Article 1

A Complete Guide on Types of Taps for Threading

Threading is an important processing method that involves using a thread tap to cut the threaded part of a
pair of matching metal fasteners. It has many uses, for example, manufacturers in the automotive and
medical industries use threaded holes to hold parts together as it makes parts more compact and eases
transportation and usage.

There are many different types of tap machinists and engineers use and choosing the right thread tap
determines the outcome of a project. In this article, there is a detailed explanation of what a thread tap is,
how to use a tap for threading, and the considerations for choosing the right tap.

Contents hide

I What is a Thread Tap?

II Components of a Tap

III Types of Taps

IV How To Use a Tap for Threading?

V Considerations for Choosing the Right Tap Type

VI Find Thread Tap Size with a Chart

VII Conclusion

VIII FAQs

What is a Thread Tap?

A thread tap is a specially designed tool that cuts and restores internal threads into drilled holes in metal
parts. Many thread taps are manually operated using a tap handle while other automatic ones make use
of drilling machines. The parts of the tap have characteristic shapes that differentiate them.

Also, threaded taps are typically made of hardened chrome steel, solid carbide, or high-speed steel. The
external threads on the fasteners are made using a die. The threaded hole and the fastener serve as a
connection mechanism for parts when the use of conventional bolts and nuts is not applicable.
Components of a Tap
Though different tap types have distinct features, the following are the main components.

Body: This is the longest and most important part. The body of a tap is what does the cutting. It contains
both the thread chamfers and the full threads. The number of these varies depending on the tap type.

Shank: The shank is located just above the body. It is smooth and has a cylindrical shape. The shank
length differs according to tap type. This part has marks that indicate the distance between the threads.

Tang: This is the squared-shaped part above the shank. Based on the mode of operation (manual or
automatic), manufacturers fix the tang on a holder to rotate the tap.

Flutes: Flutes are grooves on taps that accommodate and expel the chips during tapping. They come in
different types and shapes based on the tap type. As a standard, a tap contains 2-4 flutes which can be
angular, straight, or spiral.

Land: The land is the threaded part between the flutes.

Heel: This is the slanted area behind the threads.

Cutting Face: This is the surface of the tapping tool that comes in contact with the material.

Types of Taps
Different tap types can cut different types of threads in holes. The following are the different taps for
threads with their distinct feature

Hand Taps

The taper tap, plug tap, and bottoming tap make up the complete set of hand taps.

-Taper Tap

This tap has 8-10 thread chamfers before the full cutting diameter. Hence, manufacturers use it as a
starter tap for blind holes in hard materials. A taper tap offers a more delicate and gradual cutting motion.
It is not ideal as the only tap for a project because it cannot thread to the bottom.

-Plug Tap
The use of a plug tap just after the taper tap is not uncommon. Plug taps give the desired depth and form
to already drilled holes. It has 3-5 threads that taper from the tip. Hence, it gives a more forceful cutting
action than the taper tap.

-Bottoming Tap

Manufacturers use bottoming tap as the last tap for a project. This is because it has 1-2 thread chamfers
and does not align with the hole when used to begin a threading process. Also, as bottoming tap cuts, it
cleans the already-cut threads.

Master Tap

The master tap is like the taper tap. The difference lies in the number of flutes. The master tap has 7-10
flutes with more cutting faces. Master taps are applicable in cutting clean threads in hard and strong
materials.

Gas Tap

Gas tap deeply cuts gas-type threads for merging hydraulic fittings and pipes. It has 1-2 thread chamfers
that work perfectly with both cylindrical and conical-shaped holes.
Machine Tap

In contrast to the tap types described above, machine tap is fully automated. It makes use of a tap drill
machine, so lessens the occurrence of damage to the workpiece and the tap. Furthermore, this machine
simplifies the threading process as the operation requires less human labor to complete a project.

Machine Screw Tap

This tap type is not fully automated. It is used with either a manual tap handle or a tap drill machine.
Machine screw taps have 2-4 threads that taper from the tip. For this reason, they can thread deep holes
manually in many material types. Manufacturers use machine screw taps for repairs, routine
maintenance, and rethreading where accuracy and tight tolerance are not essential.
Extension Tap

This tap type is like the hand taps. However, extension taps have a long shank above the body. Hence, it
can reach holes that are considered inaccessible like the hub of a pulley.

Bend Shank Tap

Its distinct feature is a bent handle that extends from the tang. This allows for continuous tapping without
stopping the drilling machine at intervals.

Stay Bolt Tap

This tap is 15-20 inches in length and is used in the locomotive-broiler application. The stay bolt taps
threads holes that match the diameter of the stay bolt nut.

Spiral Fluted Tap

Compared to conventional straight flutes, the flute in this tap is spiral-shaped. This feature aids in the
easy removal of chips from the tapped hole. A spiral-fluted tap is perfect for soft metals and metals that
produce short chips.

Fluteless Tap
As the name implies, this taps type has threads throughout the body without flutes. Fluteless tap uses the
pressure deformation technique to cut threads into holes without chip removal. This allows for faster-
cutting speed and high-quality threads. However, it is only compatible with soft metals.

How To Use a Tap for Threading?

Tapping threads in a hole is a careful and stepwise process. Follow these steps to make high-quality
threads.

Clamping Process

Before drilling and tapping threads, it is important to hold the workpiece in place using a vice or other
workholding tools. This is because proper clamping eases the drilling process. Any slight movement
during drilling can result in flawed final parts. To do this:

● Clean the workpiece.

● Place the workpiece in the middle of the vice jaw. For larger workpieces, clamp directly
on the workbench.

Note: It is important to control the clamping force to avoid any form of damage.

Drilling Operation

To drill that perfect hole:

● Draw a circular mark using a pencil indicating the area to be drilled.

● Apply a lubricant to the drilling tool. Using consistent speed and pressure, drill a
cylindrical hole using the most appropriate type of drill bits.
● Straighten the hole using a drill and a motor.

The bolt used will determine the size of the hole. Ideally, the diameter of the hole should be smaller. This
is because the threading process further expands the hole. However, there is a standard chart(in the
below section) that matches the size of the bolt to the diameter of the hole.

Note: One ought to be careful when drilling blind holes. The drilled hole should be a little deeper than the
length of the bolt.

Tapping Operation

The process of tapping holes is straightforward. To do this:

● Depending on the tap type, attach the tap to a tap handle or tap drill machine.
● Apply lubricant directly into the hole and the tip of the tap.
 ● Align the tap with the hole till you encounter resistance. As standard, for every 360-
degree clockwise turn, make a 180-degree anticlockwise rotation. This helps to break up
the chips and make room for the tap’s cutting teeth to continue cutting.

Considerations for Choosing the Right Tap Type

There are many types of taps in the market. Choosing the right tap for a project determines the outcome
of the threading process. Consider the following when selecting a thread tap.

Type of Workpiece

Engineering materials have different levels of hardness. Hence, the tap type manufacturers use varies
depending on how hard or soft the material is. Some taps have special features that make them more
suitable for some materials. For instance, fluteless taps are ideal for soft metals while machine taps work
better with harder materials because it is fully automated.

Tap Material

In general, taps are made of high-speed steel or carbide steel. The material one is working with
determines which one to go for. Manufacturers use taps made from high-speed steel for soft metals like
copper, lead, magnesium, aluminum, and related alloys. high-speed steel taps provide more controlled
and slower cutting action.

On the other hand, carbide steel taps are strong and cut threads faster in very hard materials like cast
iron, titanium, brass, stainless steel, nickel, and other hard alloys. This is because they can withstand the
friction and heat generated when tapping threads.
Type of Holes

The depth of the drilled hole determines the tap one would use. Different tap types have a varying number
of thread chamfers. The thread chamfers serve as a support system to guide the tap as it threads. Only
the full threads produce the cutting effect. Considering this, taps having 1-3 thread chamfers make deeper
holes. This is especially important for blind holes.

Cutting Speed

Some tap types are specially created for use in high-speed production. If speed is a determining factor,
spiral pointed taps, fluteless taps, or taps that are automatically operated may be ideal. For spiral-fluted
taps, the spiral or helical-shaped flute pulls the chips away from the tapping direction. This reduces the
time spent to remove the chip build-up. This advantage applies to fluteless taps that produce no chips.

Find Thread Tap Size with a Chart

Different types of taps come in different sizes. The size of the drilled hole determines the size of the tap. If
the size of the drilling tool is greater than the thread taps, the final threaded holes will be larger than the
fastener. On the other hand, a smaller drill diameter will create holes too small for the tap tool. This can
damage the thread tap and the workpiece.

To prevent this, one can use the boring machining process to expand the drilled hole as needed. The
standard formula for calculating the size of the drill is:

size of the drill= 7/8(size of the tap) – 1/32

The Chart to Determine Thread Tap Size

Tap size Major mm per Drill Size

 Diameter thread (mm)
(mm)

M1.6 × 0.35 1.6mm 0.35 1.25mm

M2 × 0.4 2mm 0.4 1.6mm

M2.5 × 0.45 2.5mm 0.45 2.05mm

M3 × 0.5 3mm 0.5 2.5mm

M3.5 × 0.6 3.5mm 0.6 2.9mm

M4 × 0.7 4mm 0.7 3.3mm

M5 × 0.8 5mm 0.8 4.2mm

M6 × 1 6mm 1 5mm

M8 × 1.25 8mm 1.25 6.8mm

M8 × 1 8mm 1 7mm

M10 × 1.5 10mm 1.5 8.5mm

M10 × 1.25 10mm 1.25 8.8mm

M12 × 1.75 12mm 1.75 10.2mm

M12 × 1.25 12mm 1.25 10.8mm

M14 × 2 14mm 2 12mm

M14 × 1.5 14mm 1.5 12.5mm

M16 × 2 16mm 2 14mm

M16 × 1.5 16mm 1.5 14.5mm

M18 × 2.5 18mm 2.5 15.5mm

M18 × 1.5 18mm 1.5 16.5mm

M20 × 2.5 20mm 2.5 17.5mm

M20 × 1.5 20mm 1.5 18.5mm

M22 × 2.5 22mm 2.5 19.5mm

M22 × 1.5 22mm 1.5 20.5mm

 M24 × 3 24mm 3 21mm

M24 × 2 24mm 2 22mm

M27 × 3 27mm 3 24mm

M27 × 2 27mm 2 25mm

Conclusion
A thread tap accurately cuts internal threads in holes in parts to install fasteners where conventional bolts
and nuts are not ideal. Manufacturers use different types of taps to thread drilled holes. One can thread
using many tapping machining techniques to make custom parts.

WayKen has made machining services easy. We are the right choice for your threading machining
projects. Our engineers and machinists are experts in tapping techniques. With us, you will be sure to get
high-quality and affordable machined parts. Feel free to contact us if you have questions about threading
holes.

FAQs
Can you thread holes using a die?

The internal threads in a drilled hole and the external threads on a bolt or nut makes up a pair of mating
metal fastener. The die tool cuts external threads on a bolt or nut. Both thread types must accurately fit
into each other.

Why lubricate a thread tap before tapping?

It is important to apply lubricants directly into the drilled hole and the tip of the tap before tapping a hole.
This aids the easy removal of chips and helps to reduce friction.

Can thread taps rethread an existing hole?

Yes, a thread tap can cut threads in an existing hole. Engineers and machinists across many construction
industries have a tapping set in their toolbox to clean out and rethread holes as needed.
Article 2

10 Different Types of Taps for Threads [Definitive Guide

This is your complete guide to types of taps. There are many different types of thread taps, and
knowing exactly when to use each will make your tapping faster and easier.

Note: If you're familiar with tap types, but need to learn best practices in their use to avoid breaking
taps, try our article and video 7 Ways to Avoid Breaking Taps.

A great variety of thread taps are available with varying advantages and disadvantages:

Hand Taps (Tap Set Taps, Straight Flute Taps)

 Hand taps, typically bought at the local hardware store, are the most common types of taps, but they
are generally to be avoided for CNC work. Buy some good quality taps and try tapping by hand
versus the hardware store set of thread taps. You'll be surprised at how much better taps made for
machines work.

One applicable standard for Hand Taps is ISO 529.

There are two types of Hand Taps:

Taper Tap

A taper tap has quite a lot of taper to help it ease into cutting threads gradually. Typically, the first 8
to 10 threads are tapered. Taper Taps are the most common types of taps and are typically what
you'll have in a Tap and Die Set.

Bottoming Tap

A bottoming tap has almost no taper at the end because it is designed to thread all the way to the
bottom of its reach. Only 1 to 1.5 threads will be tapered.

Bottoming Taps are useful for threading blind holes. It's desireable to thread most of the hole with a
Taper Tap first, and then finish the bottom of the hole with a Bottoming Tap.

Plug Tap

Plug Taps are in between Bottoming and Taper Taps because they have 3-5 threads tapered, which
is more than a Bottoming Tap and less than a Taper Tap.

Unfortunately, terminology is not always consistent. Some vendors call these "Second Taps" and
refer to Bottoming Taps as Plug Taps. Check to be sure what you're getting and using.
Power Taps

These are the types of taps you should choose from for CNC applications or for manual machining
work.

Spiral Point Taps (Gun Nose or Bull Nose Taps)

These thread taps have a spiral cut with relief grooves. They're common and look like most of the
hand taps you'll see around. But, the spiral angle on the front cutting edges helps eject the chips
and the angled edge also gives superior cutting performance. Hence, they're really the least
expensive thread tap you might consider using for power tapping, and can be run at slightly higher
speeds than hand taps.

Like hand taps, sprial point taps can be had as a taper tap has a tapered end, or a plug tap
(intended for blind holes) has much less taper.

They're cheaper than the other two types, but I typically prefer the other two. The primary
disadvantage of these is they push the chips ahead of the tap-down into the hole in other words.
This is not a big deal for through holes, but is a bad idea for blind holes.
Spiral Flute Taps or Gun Taps

Spiral Flute Taps have an open spiral just like an endmill. Their primary advantage is they eject
chips up and out of the hole. They're always preferable over spiral point taps when you have a blind
hole.

They're also preferable for an interrupted hole where another feature intersects because the spiral
helps restart the threading past the open feature.
 Sometime, take a spiral flute tap and a regular hand tap and tap a couple of identical holes by hand.
You'll be shocked at how much less effort the spiral flute tap requires. Choosing the right types of
taps really helps!

Interrupted Thread Tap

These thread taps only have a tooth for every other thread. The idea is to provide improved chip
extraction. Removing every other tooth helps break chips and also provides more room for the chip
to escape and for lubricant to come in and do its job.

Types of Taps for Tapered Threads: Pipe Taps

As you might expect, Pipe Taps are the types of thread taps used for tapping pipe threads. There
are both straight and tapered pipe taps depending on whether the pipe thread is intended to be
straight or tapered. The photo shows a typical NPT Thread Pipe Tap. You can see the taper of the
NPT thread profile.
 Taps for tapered pipe threads have to work harder because you can't drill a tapered hole. There's
quite a lot more material they must remove at top of hole than bottom. Use a pipe taper reamer to
taper the hole so the tap doesn't work so hard.

Form or Roll Taps (Thread Forming Taps)

Thread Forming taps don't cut threads at all. Instead they cold form. Threads made this way are
often called "rolled" threads.

With this process, the metal is pushed out of the way and compressed into position rather than
being cut. There are no chips to remove. As a result, the taps themselves are less likely to break
and the threads they make are stronger. If your application allows Form Taps, they are generally the
best thing going for those reasons.

Form Taps do require different feeds and speeds and they require a different starting hole size, so
be aware of that before using one.

While many believe they're only good for soft materials like aluminum, they can actually be used on
materials up to a hardness of 36 HRC, which is about 340 BHN. That covers a surprisingly wide
range of materials including a lot of steels.

I will almost always choose a Form Tap over a Cutting Tap out of the available types of taps if the
material isn't too hard for thread forming.

Kelly offers this tip for form taps:

 "One minor hiccup with quite a few of the roll forming taps...unless they have a groove to allow
cutting oil to escape, or there is no room at the root or crest of the thread, the oil will build up back
pressure as the tap goes in, and eventually act like solid metal plug blocking further entry of the tap
into the hole. I figured this out the hard way after breaking a few taps."

Extension Taps (Long Shank Taps)

These are just thread taps with a long shank to facilitate reaching difficult holes that are blocked by
other features on the part.

Exotic Types of Taps: Punch Taps

This proprietary technology jointly developed by Audi and Emuge can save you up to 75% of your
tapping cycle time. Check out our article for more about Punch Taps.
Standard Tap Markings

Taps are marked on the shank so you can tell at a glance what kind of thread tap you're dealing
with. The markings typically will include:

● Nominal Size: This is the description of the thread size that tap will make.
● Thread Form Symbol: This describes the thread family.
● Tap Material: Usually Carbide or HSS
● Pitch Diameter LImit: Tells what tolerance thread will be made.

Pitch Diameter Limits (Threads < 1" in diameter)

L1 = Basic to Basic minus .0005

H1 = Basic to Basic plus .0005
H2 = Basic plus .0005 to Basic plus .0010
H3 = Basic plus .0010 to Basic plus .0015
H4 = Basic plus .0015 to Basic plus .0020
H5 = Basic plus .0020 to Basic plus .0025
H6 = Basic plus .0025 to Basic plus .0030

Note: You can find these limits in G-Wizard's thread database too.

Thread Form Symbols / Abbreviations

ACME 60° STUB 60° Stub thread form

ACME STUB Stub Acme thread form
ACME-C Acme thread - centralizing
ACME-G Acme thread, general purpose
ANPT Aeronautica National Form taper pipe thread
AWWA American Water Works Association
BA British Association Standard thread form
BSF British Standard Fine thread series
BSPP British Standard Pipe Parallel
BSPT British Standard Pipe Taper
BSW British Standard Whitworth
MM ISO Metric thread form
N BUTT American Buttress screw thread
NC American National Coarse thread series
NEF American National Extra-Fine thread series
NF American National Fine thread series
NGO American National gas outlet threads
NGT American National gas taper threads
NH American National hose & fire hose coupling
NM National Miniature thread series
NPS American Standard straight pipe thread
NPSC American Standard straight pipe thread in couplings
NPSF American Standard internal straight pipe thread (dryseal)
NPSH American Standard straight pipe thread for hose couplings & nipples
NPSI American Standard intermediate straight pipe thread (dryseal)
NPSL American Standard straight pipe thread for locknuts
NPSM American Standard straight pipe thread for mechanical joints
NPT American Standard taper pipe thread
NPTF Dryseal American Standard taper pipe thread
NPTR American Standard taper pipe thread for rail fittings
NS Special threads of American National Form
PTF Dryseal SAE Short Taper pipe thread
SGT Special Gas Taper thread form
SPL-PTF Dryseal Short Taper Pipe thread
STI Special Threads for Helical Coil Wire Screw Thread Inserts
UN Unfied and American thread series
UNC Unfied and American Coarse thread series
UNEF Unfied and American Extra-Fine thread series
UNF Unfied and American Fine thread series
UNIV Unified Miniature Thread Series
UNJ Unified Thread Series with Controlled Root Radius
 UNJC Unified Coarse Thread Series with Controlled Root Radius
UNJF Unified Fine Thread Series with Controlled Root Radius
UNR Unified Constant Pitch thread series with Controlled Root Radius
UNRC Unified Coarse Thread Series with Controlled Root Radius
UNRF Unified Fine Thread Series with Controlled Root Radius
UNS Unfied and American threads of selected special diameters and pitches

Article 3

What Is Tapping?
Tapping involves creating threaded holes in a workpiece. These threads are designed to enable

engagement with machine screws, bolts, and other threaded features. It allows them to be securely

engaged in their intended holes. Anywhere that a machine screw or bolt engages with a component, the

hole is likely to have been tapped.

The process involves the use of a cutting tool called a tap. The tap is essentially a screw made of hard

material, with straight or helical flutes cut into it. These flutes expose cutting edges that perform the

thread-cutting process. The tap can be operated manually using a tap wrench, engaged using a drill press

tapping machine, or employed in a manual or CNC machine tool setup.

The precision of tappings is crucial to ensure that threaded connections are strong, secure, and function

as intended and the cut thread can appropriately resist the expected shear forces resulting from a

fastener being tightened into the threaded hole.

Appropriate tool selection, hole preparation, cutting speeds, and lubrication are all factors in achieving

successful tapping operations, resulting in whole, strong, and cleanly cut threads.

The Purpose of Tapping in Machining

A tapping machine, tapping press, or tapping center is a specialized machine that facilitates accurate and

efficient tapping of multiple holes. They are designed to operate a standard series of taps to cut internal

threads into pre-drilled holes in workpieces. Tapping facilitates precise control over thread depth and the

cutting process, ensuring greater uniformity and consistency of threads in multiple workpieces.
 Additionally, they improve operator efficiency by more rapidly creating threaded holes with better

repeatability despite the faster throughput, compared to manual tapping.

Automated tapping machines further reduce the dependency on operator skill by removing all manual

operational processes and allowing the operator to act simply as a loader/unloader. Tapping machines

can generally accommodate a very wide range of workpiece sizes and materials, though workholding may

require customization for high efficiency and precise part location. They can be operated with all types of

taps to produce varied thread profiles—standard metric, UNF, UNC, acme, etc. Automation in turn

reduces unexpected forces and poor operation, reducing breakages and wear of taps.

Comparing Tapping with Drilling

Tapping is not the same as drilling. The action of tapping is to use a straight fluted multi-point thread-

cutting tool—the tap—to remove material from the wall of a hole, to impose a thread form of a larger tip,

or maximum diameter than the hole into which it was cut.

In certain instances, the drilling operation that precedes tapping is performed with a combination drill and

tap tool, in which the drill presents the cutting tip that forms the hole, and a tapping region is machined

onto the flutes above the tip, to switch from drilling to tapping as the operation proceeds. These tools are

unusual in that they use helical flutes like a twist drill, to allow effective bulk chip clearance from the

drilling stage and they are used for relatively low-criticality and low-precision threading.

The Process of Tapping

Thread tapping is a manual or machining process that cuts the full spectrum of smaller-diameter internal

threads. The taps are positioned at an angle between the cutting face and the tap's axis which is referred

to as the helix angle. This allows the cutting face to engage more progressively in machine taps, reducing

cutting forces and tool wear, as well as improving surface finish.

As the tap rotates, the cutting faces engage with the wall of the hole, dragging the sharp edges of the

cutting faces into the material and removing the material to expose the thread. This action involves the

cutting faces of the tap shearing material away, creating the thread profile. Swarf is generated during the

process which is evacuated via the flutes of the tap.

 At the tap tip, a taper is applied which reduces the cutting teeth from their full height. This enables multi-

pass cutting in a single rotation, as many teeth of increasing height engage with any given point, as the

tap draws itself into the hole by rotation. Proper lubrication is essential, to reduce friction and tool wear

and to reduce the incidence of snagging, in which the cut stalls and the risk of tooth or shank breakage

greatly increases.

Precise alignment of the tool to the hole is also essential. At the start, there is generally little to no

engagement between hole and tap, so the alignment must be imposed by the operator or the machine.

Errors in tap alignment will result in defective threads.

Different Types of Taps

Various types of taps are used for specific applications and materials. The three main types are:

1. Taper or Starter Taps: Taper or starter taps have a gradual taper cut onto the first 20–30% of
their functional length, allowing gradual engagement and better self-centering when starting
threads.

2. Plug Taps: Plug taps have a shorter tapered region and are used to progress threading more
deeply after a taper tap has started the process.

3. Bottoming Taps: Bottoming taps have no taper but a slightly chamfered tip to ease engagement
with an already part-formed thread. They are used to thread the bottom of blind holes.

Different Tapping Processes

The different tapping processes are listed below:

1. Tapping on the CNC Lathe

Tapping on a CNC (Computer Numerical Control) lathe involves cutting threads into a workpiece using a

tap or a thread mill. First, secure the workpiece in the lathe's chuck. Then securely insert the tapping tool

into the lathe's tool holder or turret. Use the CNC controls to jog—align the tapping tool with the

workpiece, where X-Y axis adjustments are available. Set appropriate spindle speed and feed rate for

tapping.

Next, load the CNC program that includes the tapping operation. Once the CNC program is initiated, the

lathe will move the tapping tool into the workpiece, engage it with the workpiece, and begin cutting
 threads with coolant applied. While tapping is in progress, the CNC control continuously monitors the

process. More advanced equipment may include features to detect issues like excessive torque, tool

breakage, or tap wear.

2. Hand Tapping

Manual tapping is a more delicate and skilled operation and requires some experience. It starts with firmly

mounting the workpiece in a vice or work holder. Then, select an appropriate tap for the required thread

and cutting stage (taper or plug for starting to thread a hole). Fit the tap to a suitable tap wrench, ensuring

it is firmly clamped. Next, apply an appropriate cutting compound to the tap and engage its taper with the

hole.

While applying axial load to force the tool, rotate the wrench to begin to engage the cutting faces with the

bore. This will feel uncertain at the start but will quickly centralize if the engagement remains straight.

Once the cut feels secure, advance by a half turn and then retract by a quarter turn, to break off the chips

formed. Complete the first pass to finish the entry threads. Change to a bottoming tap if the hole is blind

or the space beneath is restricted. Ensure perfect engagement as a second (misaligned) start will create

a weak and damaged thread that is at risk of cross-threading when a fastening is fitted. Complete the

thread, remove the tool, and clean the swarf.

Choosing a Tapping Tool

Choosing the right tapping tool requires consideration of a few factors. First, determine the specific

requirements of your application. Consider factors such as: the material being tapped, the type of hole

(through-hole or blind hole), and the thread size, profile, and pitch. Next, determine the equipment and

methods to be used: manual, manual machine, lathe, mill, or CNC machine. Consider the coating or

surface treatment of the tapping tool to reduce friction and heat generation during tapping of extensive

workload. Ensure that the tap's direction matches the equipment setup direction.

Next, consider the required thread tolerance, pull-out strength, and quality. Also, consider the tap's design

for effective chip evacuation. Taps with spiral flutes or spiral point (gun) taps are better at removing chips

from the hole. Determine if your application involves through-hole or blind-hole tapping and select the

degree of taper accordingly. Ensure that your tap is compatible with your tapping equipment.
 It is often helpful to test options on a sample workpiece to determine which one performs best for your

specific needs. Choosing an appropriate tap is essential to cutting accurate and repeatable threads

The Size of the Tapping Tool Affects Accuracy

The size of the tapping tool, specifically its diameter and pitch, can significantly affect the accuracy of the

threading operation, depending on several factors. For example, using an improperly sized tap can result

in threads that are too loose or too tight, leading to functional issues. Proper alignment and centering are

also essential for creating straight and accurate threads. If the hole is undersized, precise alignment will

be hard to achieve. Additionally, the relative size of the tap and hole affects how much material it engages

with during the tapping process. Heavier engagement requires more force, which can result in

inaccuracies, tool breakage, or damage to the workpiece.

Choosing a tap of appropriate length can improve precision and is necessary to allow full depth of thread

over the required region. The size and design of the tapping tool's flutes or grooves play a role in chip

evacuation during tapping, reducing the risk of thread or tool damage.

The Depth of Tapping a Thread

The limiting factor in the depth of thread cutting is the length of the tap shank, or in some cases the

accessibility of the tool in presenting to the workpiece over a long tapping process. For example, it is

typical for an M3 tap to be able to cut a thread to the limit of its 40–50 mm shank, as long as the tap

wrench or machine chuck can approach close to the surface without obstruction.

Advantages of Tapping
Tapping offers significant advantages such as:

1. A cost-efficient method for creating threads in materials, compared with all other methods.
2. Produces precise and accurate threads.
 3. Can be applied to the widest range of materials, from metals to composites, from ceramics and
plastics, and also natural materials such as wood.

4. It is quick, especially for small-scale production.

5. Provides consistent thread quality and pitch when performed well.
6. Generates minimal waste.
7. Allows for the creation of various thread types, such as: metric, UNF, UNC, and specialized
threads like NPT and acme.

8. Can be used for both through holes and blind holes.

9. Manual tapping is straightforward and low-cost to set up, and automated CNC tapping machines
offer precise control and repeatability.

10. Is valuable for repairing damaged threads in existing components, extending their service life.

Disadvantages of Tapping
While tapping is a widely used method for creating threads in various materials, it does have some

disadvantages and limitations such as:

1. Can be challenging and less effective in extremely hard materials, requiring specialized taps or
alternative threading methods.

2. Tapping tools can wear out relatively quickly, especially when used on harder or abrasive
materials.

3. Taps are relatively delicate cutting tools that break or chip easily.
4. The length of threads created by tapping is limited by the length of the tap.
5. Ensuring consistent and high-quality threads can be challenging, using manual tapping.
6. Effective chip evacuation is essential to prevent tap breakage and maintain thread quality, and
this can be challenging—especially in blind holes.

7. Manual tapping relies heavily on operator skill and experience. In manual tapping, there is a risk
of cross-threading, especially when starting the tap incorrectly, which can damage both the tap
and the workpiece.

The Difference Between Tapping and Thread Milling

Tapping and thread milling are two distinct machining processes used to create threads in a workpiece,

each with its advantages and disadvantages. For example, tapping uses a tap that has all of the thread

diameter and tooth profile in its form, and it cuts the threads as it rotates concentrically with the hole.

Thread milling, on the other hand, uses a milling cutter with multiple flutes or inserts to create threads.

Instead of cutting threads with a single-point tool like a tap, thread milling removes material by spiraling

along the desired thread path.

Additionally, tapping is a faster and more straightforward process for creating threads in certain

applications but has limitations in terms of thread type, diameter, and depth. Thread milling offers greater

flexibility and versatility. The choice between tapping and thread milling depends on the specific needs of

the machining operation and, most of all, on the intended diameter of the bore to be threaded.

Article 4

How to choose the right type of tap

When choosing the right tap, there are several factors that need to be considered. Follow these steps to

find the best tap type for your application.

Different tapping tool types

Which tapping tool you use depends on what type of hole you want to thread.

Thread form type and material (ISO application area)

Find the right thread form type and material to thread.

Threading chamfer type

The type of tapping hole determines which chamfer type you use.

Different tapping tool types

Tapping tools are divided into four types: straight flute tap, spiral point tap, spiral fuse tap, and forming
tap. Which type you use depends on what type of hole you want to thread, blind hole or through hole, and
the component material.
Straight flute tap

Spiral point tap

Spiral fuse tap

Forming tap

Cutting taps

With a cutting tap, the tap cuts the material, and chips are generated.

Forming taps

Advantages compared to cutting taps:

● Forming is usually faster than ordinary thread cutting

● Deep threads down to 3.5 × D are possible without chip removal problems
● Forming taps often give a longer tool life
● One type of tool can be used in different materials and for both through and blind holes
 ● Forming taps have a stable design which has a lower risk of breakage
● Threads with the right tolerance are guaranteed
● No chips are generated
● Up to 100% stronger thread (higher stripping strength)
● Lower surface roughness on thread

Pre-conditions for effective use:

● Not all materials are suitable since there is a certain ductility needed
● Recommended tensile strength limit is 1200 N/mm2
● A precise drilled hole diameter is required
● Good lubrication is imperative

Thread form type and material (ISO application area)

Tapping tools are available in many thread forms. You need to know which thread form type you want to
thread.The table below shows which thread forms are available for tapping tools optimized for specific
materials and tapping tools optimized for versatility.

Versatility

M, MF, M, MF, M, MF, UNC, M, MF, M M, MF,

UNC, UNF UNC, UNF, G UNC, UNF UNC, UNF,

UNF, G, G, NPT,
NPT, NPTF NPTF, EGM
 Threading chamfer type

The tap chamfer is the tapering of the threads that distributes the cutting action over several teeth.
Usually, the type of hole to be tapped determines which chamfer type should be used. There are three
common chamfer types: B, C, and E.

Chamfer type B = 3.5–5 × threads

Long chamfer:

● High torque
● Best surface quality
● Thin chips
● Low pressure at the chamfer
● Longer tool life
● Most common for spiral point tap

Chamfer type C = 2–3.5 × threads

Medium chamfer:

● Low torque
● Good surface quality
● Normal thick chips
● Normal pressure at the chamfer
● Normal tool life
● Most common design
● Standard chamfer for blind holes
● Most common for spiral flute tap
 Chamfer type E = 1.5–2 × threads

Short chamfer:

● Low torque
● Good surface quality
● Thick chips
● High pressure at the chamfer
● Shorter tool life
● Extreme design
● To be used when there is not much clearance in the bottom of the hole

Point/chamfer matrix

The type of point on taps is a result of the tap production. Below is a chart showing the points and
chamfers that are commonly used together, sorted by tap diameter.

1 Full point 2 Reduced point 3 Internal point 4 Removed point

Tap, mm Tap, inch B 3.5 - 5 C 2 - 3.5 E 1.5 - 2

 ≤5 >No1-No10 1 1 1

>5 ≤6 >No12-1/4 1 1, 2 1

>6 ≤10 >1/4-1/2 1 1, 2, 4 1, 4

>10 ≤12 >3/8-1/2 2, 3 2, 3 2, 3

>12 >1/2 3 3 3

Article 5

Taps make threaded holes so that they’re ready for fasteners like screws and bolts to be inserted or

tightened with a drill or appropriate hand tool. Turning the tap by hand creates threads inside pre-drilled

holes. They’re found in manufacturing parts, like vehicles and structures, and they’re also in flat-packed

furniture—handy for those putting it together as they won’t have to manually make these holes.

Thread Tap Types

 There are tons of different types of thread taps with many varying endpoints, tapers, and flutings. Let’s

look at 13 of them to help you decide on the right one for your needs—because, let’s face it, knowing

which one to use is a total shot in the dark.

Hand Taps

Hand taps are multifunctional and work either by hand or with a power tool. They’re used for machine

tapping in general and most materials with blind or through holes. These have straight flutes used in

shallow blind or through holes. A standard hand tap set has three separate types, which we’ll discuss

below.

Plug Taps

A plug tap has a five-thread cutting chamfer that slowly cuts away material to create the thread, starting

with the smaller diameter. They’re used when there is enough space at a blind hole’s bottom part, or to

make through-holes. They make a more complete set of threads compared to taper taps, but aren’t as

well suited to finishing threads in blind-holes as bottoming taps.

 A plug tap.

Taper Taps

These have nine-thread chamfers and the smallest diameter of any hand taps. Taper taps are typically

the starting point for blind- or through-hole applications. One of their biggest advantages is they clear out

most of the material early in the process. They shouldn’t be used for finishing the bottom of blind holes

since they can leave incomplete threads.

 A taper tap.

Bottoming Taps
A bottoming tap has the smallest thread chamfer (1.5 inches). It’s used to finish the end of a blind hole

since it can get all the way to the bottom (unlike plug and taper), but isn’t good at removing most of the

material from the hole (that’s what the other two are for).
 A bottoming tap.

Pipe Tap

Pipe taps carve threads for pipes internally for pressure-tight joints. Some pipe taps are made for

hydraulic and gas purposes, and others for mechanical joints and hose couplings. They have to be done

more carefully than other types because they’re designed to mechanically seal a joint to add pressure and

prevent leaks.
 An NPT pipe tap.

Spiral Flute Tap

The spiral flute tap has flutes wrapped around the axis in a spiral (helical) formation, making their cutting

edge weaker than a hand tap’s. They’re most often used to tap thread into blind-holes and then pull the

chippings back out of the hole.

 A spiral flute tap.

Gas Tap
Gas taps are compliant with specifications used in gas and hydraulic systems. They’re a form of pipe tap

used for cutting deep threads, and either have one- or two-thread chamfers suitable for conical and

cylindrical-shaped holes.

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Machine Tap

The growing use of machinery in manufacturing has meant an increase in machine taps, too. These have

to be durable and particularly resistant to wear. Automated machining processes (like CNC) use these

taps to create both blind holes and through holes on hard materials, where spiral flute taps won’t be

strong enough. Sometimes their cutting end is coated with titanium nitride (shown in the below image) to

give it more wear resistance and increase its lifespan.

 A machine tap with a titanium-nitride coating.

Thread-Forming Tap

Also known as fluteless taps or rolled threads, these taps don’t actually cut threads; they cold-form them

instead, during which the metal isn’t cut, but moved away before being compressed into position. No

chips are formed in the process, meaning you don’t have to remove any. These taps make stronger

threads that are less likely to break.

We suggest using form taps instead of cutting taps whenever you can, as long as the material isn’t too

hard. Lots of people think that these are only good for soft materials like aluminum, but they work with any

material with a hardness of 36 HRC (or 340 BHN). That covers a bunch of materials, including a lot of

steel types.

Pro tip: It’s important to know that form taps need different feeds and speeds, as well as different starting

hole sizes. There’s another common hiccup among quite a few roll-forming taps: the oil can build up back

pressure as the tap goes in, and eventually act like a plug that blocks the tap from getting further into the

hole. There has to be a groove to let cutting oil escape, or room at the root or crest of the thread.
 A thread-forming or fluteless tap.

Master Tap

A master tap is used in many industries. They’re known for their universal ability and are typically used to

cut clean threads in hard, strong materials. They’re not that dissimilar to taper taps but have 7–10 flutes

(as opposed to a taper tap’s 3–7) and more cutting faces.

 A master tap.

Combined Drill and Tap

A combined drill and tap lets the user drill the hole and tap threads all at once without having to switch

tools. This saves both time and money on production drilling jobs. It’s helical flute-shaped and works on a

host of materials and metals, like iron and brass.

 A combined drill and tap.

Solid Carbide Tap

Solid carbide taps are made of composite material and last a long time in all sorts of environments.

They’re very hard and wear-resistant so are used on harder materials, including sintered, ultra-fine

tungsten carbides.
 A solid carbide tap.

Extension Tap

Extension taps are similar to hand taps. Their long shanks make them useful for accessing hard-to-reach

holes, like a pulley hub.

 An extension or long-reach tap.

Spiral Point Tap

These taps are strong and made to work faster than regular taps on hard materials, and don’t need as

much power, either. They make shallow grooves that can remove more metal in one go. Some feel they

are similar to straight flute taps since they share the same general shape, but they have different cutting

faces.
 A spiral point tap.

Stay Bolt Tap

A stay bolt tap is around 15-20 inches long. It’s designed to cut threads in drilled holes for threaded

machine screws or threaded bolts to be screwed in, in the exact diameter of the stay bolt nut. They were

commonly used in installing and repairing fireboxes in steam locomotives.

Interrupted Thread Tap

This type of tap only has a tooth for every other thread. It’s designed to provide better chip extraction.

Removing every other tooth helps with breaking up the chips. It also gives more room, both for the chip to

clear out and the lubricant to enter.

 An interrupted thread tap.

Thread Tap Type—Summary

For ease of reference, we’ve made the below table so you can quickly see the main differences between

these types of thread taps (in the hole size column, “M” is the outer diameter in mm).

Type Hole Chamfer Material Uses

 Size/Type Type/Flute
Design

Plug M3–M12, 5-thread, HSS (high- Finishing

blind and straight speed threads
through steel)

Taper M3–M12, 9-thread, HSS Starting

blind and straight threads
through

Bottoming M3–M12, 1.5-thread, HSS Completing

blind straight threads to
the bottom
of blind
holes

Pipe NPT/ n/a, HSS Sealing

NPTF* straight pressure-
tight joints
Spiral flute M3–M12, n/a, helical HSS, Tapping
blind flutes coated blind holes,
HSS evacuating
chips
upwards

Gas M3–M12, 1–2-thread, HSS Gas and

cylindrical straight hydraulic
and conical systems,
deep
thread
cutting

Machine M3–M20, 3–7-thread, HSS, TiN- CNC

blind and straight coated machining,
through HSS automation
on hard
materials

Thread- M3–M12, n/a (forms HSS, Cold-

forming through threads) carbide forming
threads,
chip-free
threading
 in materials
up to 36
HRC

Master M8–M24, 7–10- HSS Clean

blind and thread, threads in
through straight or strong,
spiral hard
materials

Combined M3–M10, n/a, helical HSS, Simultaneo

drill/tap through carbide us drilling
and
tapping

Solid M3–M20, n/a, Solid Hard

carbide blind and straight/spi carbide materials
through ral with high
wear
resistance
Extension M5–M16, n/a, long HSS Accessing
blind and shank, deep or
hard-to- straight narrow
reach holes

Spiral point M3–M20, n/a, HSS High-speed

through shallow, tapping
forward with low
chip power
ejection needs

Stay bolt Custom n/a, long HSS Bolts for

sizes, shank (15– fireboxes,
large- 20-inch), steam
diameter straight trains,
holes heavy
machinery

Interrupted M5–M16, n/a, HSS Better chip

thread blind and alternating clearance
through teeth, and
straight/spi lubrication
ral access
 Thread Taps Summary: *NPT and NPTF are the standardized thread forms for pipe fittings in the U.S.
(NPT needs a sealing material, but NPTF is self-sealing)

Standard Tap Markings

Taps have marks on the shank, so you can tell with just a look what type of thread tap you’re working

with. The markings include the nominal size, which is the thread size that the tap will take. There’s also

the thread form symbol, which identifies the thread family. There’s also tap material, which is usually

carbide or HSS. It also typically shows the pitch diameter limit, which tells what tolerance thread will be

made.

Pitch Diameter Limits

Here is a quick guide for threads with a diameter of less than an inch:

● L1 = Basic (B) to B minus .0005

● H1 = B to B plus .0005
● H2 = B plus .0005 to B plus .0010
● H3 = B plus.0010 to B plus .0015
● H4 = B plus .0015 to B plus .0020
● H5 = B plus .0020 to B plus .0025
● H6 = B plus .0025 to B plus .0030

Note: You can find these limits in G-Wizard’s thread database as well.

Choosing Thread Taps

When you’re choosing which thread tap to use, there are four main factors to think about so you can up

your chances of success:

Workpiece material: Various materials have different levels of firmness and there will be a tap suitable for

each level. Some will work better than others on different materials, i.e., a machine tap works well on

harder materials, but a fluteless tap is best for soft materials.

Tap material: You’ll have to choose this according to the material of the piece you want to work on, e.g.,

carbide steel taps can cut threads quickly, and are strong enough to handle hard materials like cast iron.
Hole type: Depending on what hole you need to make, there will be a tap up to the task. Taps with 1–3

thread chamfers can create deeper holes, for instance.

Cutting speed: Some taps, i.e., spiral flute, are designed for high-speed work, while others not so much,

so you’ll have to know the speed of cutting before choosing your taps.

Article 6

Thread tapping is a crucial manufacturing method where a thread tap creates threaded parts in metal

fasteners. This is commonly seen in industries like automotive and medical, where threaded holes hold

parts together, making them more compact and convenient for transportation and use.

Machinists and engineers employ various types of taps, and selecting the right one is vital for the project’s

success. In this article, we’ll break down what a thread tap is, explain how to use it for threading, and

discuss the factors to consider when choosing the appropriate tap for the job.

Thread Tap

A thread tap is a special tool that helps create threaded holes in metal parts. It’s like a magic wand for

metalworkers! This tool is used after a hole is drilled in the metal. The tap comes in different shapes and

sizes, and you can use it by turning it with your hands or a machine. These taps are often made from

tough materials like hardened chrome steel, solid carbide, or high-speed steel. They are like superheroes

that give metal parts their special threads. The threads are like the tiny ridges on screws, and they help

hold parts together when regular bolts and nuts won’t do the trick. So, think of a thread tap as a helpful

tool that adds these special twists to metal holes, making them perfect for connecting different parts!

Types Of Taps

Various types of taps are designed for cutting different thread types in holes. The following outlines these

taps and their unique characteristics:

Hand Taps: The complete set of hand taps consists of the taper tap, plug tap and bottoming tap.

Taper Tap: With 8-10 thread chamfers before the full cutting diameter, the taper tap is often used as a

starter tap for blind holes in hard materials. It provides a gentle and gradual cutting motion but isn’t

suitable as the sole tap for a project since it cannot thread to the bottom.

Plug Tap : Following the taper tap, the plug tap is commonly used to give pre-drilled holes the desired

depth and form. It has 3-5 threads tapering from the tip, offering a more forceful cutting action than the

taper tap.

Bottoming Tap : Used as the last tap in a project, the bottoming tap has 1-2 thread chamfers and does not

align with the hole when starting the threading process. It cleans already-cut threads as it cuts.

Master Tap

Like the taper tap, the master tap differs in the number of flutes, featuring 7-10 flutes with more cutting

faces. Master taps are useful for cutting clean threads in hard and strong materials.

Gas Tap

Designed for cutting gas-type threads for merging hydraulic fittings and pipes, the gas tap has 1-2 thread

chamfers that work well with cylindrical and conical-shaped holes.

Machine Tap

Unlike the manual hand taps, the machine tap is fully automated, utilizing a tap drill machine. This

reduces the risk of damage to the workpiece and the tap, streamlining the threading process with less

manual labor.

Machine Screw Tap

Not fully automated, the machine screw tap can be used with either a manual tap handle or a tap drill

machine. With 2-4 threads tapering from the tip, it can manually thread deep holes in various material

types, suitable for repairs and routine maintenance.

Extension Tap

Like hand taps, extension taps have a long shank above the body, enabling them to reach inaccessible

holes like those in the hub of a pulley.

In summary, mastering thread tapping, commonly used in many industries, is crucial for making threaded

holes in metal parts. A thread tap is a special tool, like a magic wand for metalworkers, that adds twists to

holes, making them perfect for connecting parts. There are different types of taps, from manual ones like

taper and plug taps to automated ones like machine taps. Each tap has a specific job, and choosing the

right one depends on factors like the material and the hole depth. This guide helps professionals

understand and choose the right tap for successful manufacturing projects, ensuring metal parts fit

together smoothly and securely.

Article 7

Machine vs Hand Taps vs Roll Taps

In this section, we'll compare three different types of taps: machine taps, hand taps, and roll taps. We'll
discuss the reasons why and where you would use each type. By understanding their unique
characteristics and applications, you'll be able to make informed decisions when selecting the appropriate
tap for your specific projects.

Machine Taps: Machine taps, come in options of spiral point or spiral flute, are specifically designed for
use with machine tools such as CNC lathes and Milling machines, drill presses, manual lathes and milling
machines. Machine Taps are manufactured using special grinding processes that provide unique
geometries with optimal flute space for improved chip evacuation, the unique geometries also make them
suitable for high-speed operations. Our best performing general purpose machine tap is the Prime-X from
YG-1, with 50% higher tapping speeds!

Hand Taps: Hand taps, also referred to as first, second taps and plug taps. They are a versatile tools
commonly used for manual threading operations. They have straight flutes and a chamfer at the tip to aid
in aligning the tap with the hole. Hand taps require more care and control compared to machine taps but
offer flexibility and convenience in various situations.

Roll Taps: Roll taps, also known as thread-forming taps or cold-forming taps, are unique in their
operation. Instead of cutting the material and creating swarf they reshape the existing material to form the
thread. Roll taps have no flutes, however they are available with or without oil grooves. Oil grooves allow
cutting fluid to pass through while the forming process takes place. When using roll taps specially
calculated pre-tapping drill sizes are necessary.

Conclusion: Machine taps are ideal for high-volume, automated operations, while hand taps offer
flexibility and precision in manual threading tasks. Roll taps excel in situations where material integrity
and high-quality threads are paramount. Understanding the strengths and best uses of each tap type will
empower you to make informed decisions when selecting the appropriate tool for your specific threading
requirements.

Spiral Flute vs Spiral Point vs Straight Flute Taps

Now we'll explore the distinctions between spiral flute, spiral point, and straight flute taps. Each type has
its own advantages and best-suited applications. By understanding the differences, you'll be able to
choose the most suitable tap for your threading requirements, whether it's chip evacuation, specific hole
types, or material considerations.

Spiral Flute Taps: Spiral flute taps, also known as helical flute taps, feature a spiral-shaped flute design
that runs along the cutting length of the tap. The spiral flute geometry helps evacuate chips efficiently
during the threading process of a blind hole, the spiral flute design draws swarf out of the hole like that of
a twist drill. It is crucial that spiral flute taps are used when tapping blind holes to reduce the risk of tap
breakage.

Spiral Point Taps: Spiral pointed taps are generally stronger than spiral flute taps due to their shallower
flute design, giving them a stronger core. The flute geometry of a spiral pointed tap is designed to push
swarf forward making them first choice for tapping through holes, this is where the tap can pass
completely through the predrilled hole.
Straight Flute Taps: Straight flute taps have a straight flutes that run parallel to the tap's axis. These
taps have a simple design without spirals or points. Straight flute taps are typically used for tapping short
chipping materials such as cast iron and can be used in both blind and through holes.

Article 8

#1. Hand Taps

A hand tap set is used to manually cut an internal thread. Normally, a hand tap set consists of three taps:
taper tap, center tap and finishing tap.

The hand taps have a square shaft (square according to DIN 10) to be clamped securely in thread holding
tools. The hand taps can be clamped in an adjustable tap wrench and holding tools with ratchet.

A hand tap is a tool used to manually carve an internal thread into a piece of material ready for a screw
or bolt to be inserted in.

Hand taps are used across a variety of applications as they are multifaceted and adaptable for use by
hand as well as tapping under power.

Hand taps are also used in general machine tapping and for the majority of materials that have blind- or
through-hole conditions.

A key feature of the hand taps in comparison to other types of thread taps is the straight flutes to be used
in either a shallow blind hole or through hole.

#2. Plug Tap

A plug tap is a type of hand tap, distinguished from bottoming and taper taps by the length of its cutting
chamfer.
A 5 thread chamfer Plug tap performs similar to a Taper chamfer tap by slowly removing the material in
the thread starting with the smallest diameter of the threaded protion of the tap.

Plug taps are most commonly used for through holes and where there is enough room at the bottom of a
blind hole.

The rotation of the tap continues, more material is removed from the thread by many partial thread forms
of the tap until a full thread is created.

There are times when a Plug tap can be used to start a thread without using a taper tap first if the Plug
tap is started with a guiding center or fixture.

One of the main advantages of plug taps is that they are easy to use through holes, but provide a more
complete set of threads in comparison to taper taps. However, a plug tap is not as well suited to blind
holes as taper taps.

#3. Taper Tap.

The taper tap can be identified by the visible and pronounced tapering of the cutting edges. This provides
a very gradual and less aggressive cutting action.

The distinct feature of a taper tap is the 8 to 10 threads that taper from the tip to the full cutting force
diameter. A taper tap is most often used as a starter tap for difficult blind holes.

The gentle taper of the cutting edge is the most forgiving when tapping by hand and allows for a straight
hole to be cut in especially hard materials.

A taper tap is rarely the final tap used before completing a project, however, as the taper leaves
incomplete threads cut at the bottom of a blind hole.
#4. Bottoming Tap.

Bottoming taps have 1 to 2 tapered cutting edges before the full cutting force is engaged. Though this tap
is extremely hard to start threads with, it is capable of cutting threads all of the ways to the bottom of a
blind hole.

Bottoming taps are best used after a taper or plug tap has been used to cut the initial thread.

When rotated by hand, the bottoming taps chamfer is too short to start a thread because all the thread
form would be removed with only 1.5 threads of the tap.

Bottom chamfer taps are normally used to get close to the the bottom of a blind hole but only after Taper
and Plug chamfer taps have removed most of the material.

#5. Power Taps.

If you have manual matching work or CNC applications, then this is the right type of thread tap for you.
The above tips are generally referred to as hand taps since they are manually operated.

During operation, the machinist must periodically reverse a hand tap to break the chip (also known as
swarf) that forms from cutting. This prevents the cut material from crowding and breaking the tap.

The most common type of power-driven tap is the “spiral point” plug tap, also referred to as a “gun” tap,
whose cutting edges are angularly displaced relative to the tap centerline.

This feature causes the tap to continuously break the chip and eject it forward into the hole, preventing
crowding. Spiral point taps are usually used in holes that go all the way through the material so that the
chips can escape.
Another version of the spiral point plug tap is the spiral flute tap, whose flutes resemble those of a twist
drill. Spiral flute taps are widely used in high-speed, automatic tapping operations due to their ability to
work well in blind holes.

#6. Spiral Point Taps

These thread taps have a spiral cut with relief grooves. They’re common and look like most of the hand
taps you’ll see around. But, the spiral angle on the front cutting edges helps eject the chips and the
angled edge also gives a superior cutting performance.

Hence, they’re really the least expensive thread tap you might consider using for power tapping and can
be run at slightly higher speeds than hand taps.

Like hand taps, spiral point taps can be had as a taper tap has a tapered end, or a plug tap (intended for
blind holes) has much less taper.

They’re cheaper than the other two types, but I typically prefer the other two. The primary disadvantage of
these is they push the chips ahead of the tap–down into the hole in other words. This is not a big deal for
through holes but is a bad idea for blind holes.

#7. Spiral Flute Taps

Spiral Flute Taps have an open spiral just like an endmill. Their primary advantage is they eject chips up
and out of the hole. They’re always preferable over spiral point taps when you have a blind hole.

They’re also preferable for an interrupted hole where another feature intersects because the spiral helps
restart the threading past the open feature.

Sometimes, take a spiral flute tap and a regular hand tap and tap a couple of identical holes by hand.
You’ll be shocked at how much less effort the spiral flute tap requires. Choosing the right types of taps
really helps!
#8. Interrupted Thread Tap

These thread taps only have a tooth for every other thread. The idea is to provide improved chip
extraction. Removing every other tooth helps break chips and also provides more room for the chip to
escape and for lubricant to come in and do its job.

#9. Pipe Taps

As you might expect, Pipe Taps are the types of thread taps used for tapping pipe threads. There are
both straight and tapered pipe taps depending on whether the pipe thread is intended to be straight or
tapered. The photo shows a typical NPT Thread Pipe Tap. You can see the taper of the NPT thread
profile.

Taps for tapered pipe threads have to work harder because you can’t drill a tapered hole. There’s quite a
lot more material they must remove at top of the hole than at the bottom. Use a pipe taper reamer to taper
the hole so the tap doesn’t work so hard.

#10. Forming tap

A quite different kind of tap is a forming tap. A forming tap, aka a flueless tap, simply forcefully displaces
the metal into a thread shape upon being turned into the hole, instead of cutting metal from the sides of
the hole as cutting taps do.

A forming tap closely resembles a cutting tap without the flutes, or very nearly just like a plain thread.

There are lobes periodically spaced around the tap that actually do the thread forming as the tap is
advanced into a properly sized hole. The threads behind the lobes are slightly recessed to reduce contact
friction.

Since the tap does not produce chips, there is no need to periodically back out the tap to clear away
chips, which, in a cutting tap, can jam and break the tap.
Thus, thread forming is particularly suited to tapping blind holes, which are tougher to tap with a cutting
tap due to the chip build-up in the hole. Forming taps only work in malleable materials such as mild steel
or aluminum.

Formed threads are typically stronger than cut threads. Note that the tap drill size differs from that used
for a cutting tap as shown in most tap drill tables and that an accurate hole size is required because a
slightly undersized hole can break the tap.

Proper lubrication is essential because of the frictional forces involved; therefore, lubricating oil is used
instead of cutting oil.

#11. Extension Taps

Extension taps have long shanks. This allows you to get to hard-to-reach holes. “Long shark tap” is
another name of this thread tap.

#12. Punch Taps

This thread tap uses the technology of Audi and Emuge that allows tapping cycle time to fall 75%. It’s a
great tool to have for your thread tapping needs.

#13. Gas Tap

A gas tap is a type of threading tap. It is commonly used to cut deep threads for merging pipes and
hydraulic fittings. Gas taps are ideally suited for both conical and cylindrical shaped holes due to their
one- or two-thread chamfers, unlike the much wider nine-thread chamfer taper tap.

#14. Machine Tap

Machine taps are used for threading and have grown in popularity and importance recently in line with the
increased use of machinery in production.

Threading tools used in these machines are now required to be increasingly wear-resistant and durable.

Machine taps are fully automated and used in threading hard materials and are suited to both blind holes
and through holes. Machine taps are used for hard materials, unlike spiral flute taps.

#15. Master Tap

A master tap is a variety of threading tap and is widely used across a range of industries. Master taps are
known for their universality and diversity and are most commonly used to cut clean threads in strong and
hard materials.

Master taps are similar to taper taps, however the key difference is in the number of flutes. The master
tap has more cutting faces and on average 7 to 10 flutes.

#16. Combined Drill and Tap

A combined drill and tap enables the manufacturer to drill the hole and tap threads in one operation,
without the need to switch tools, saving both time and money on a production drilling job.

It can be used for a variety of materials, including: aluminum, malleable iron, and brass. Similar to a
spiral flute, this implement has a helical flute design.

#17. Solid Carbide Tap

Solid carbide taps are threading implements made of composite material that consists of sintered ultra-
fine tungsten carbides.
They are commonly used on hard materials as solid carbide has an extremely high hardness and wear
resistance. One of the key benefits of solid carbide taps is the long life span of this tool, even in more
challenging working environments.

#18. Fluteless Tap

A fluteless tap is a form of threading tap that utilizes a pressure deformation technique to cut threads into
a material. Fluteless taps are used only on softer metals and, unlike other forms of threading taps, the
threads through the body are without flutes.

Similar to a thread-forming tap, there is no chip removal with this form of threading and this allows for
high-quality threads with fast cutting speed.

#19. Machine Screw Tap

Machine screw taps are used to carve threads into the material and have on average 2–4 threads
tapering from the tip. By their design, machine screw taps are used to manually thread deep holes in a
variety of material types.

Manufacturers utilize the machine screw tap for routine maintenance, repairs, and rethreading in
situations in which tight tolerance and accuracy are not necessary.

Unlike machine taps, machine screw taps are not fully automated—they are used alongside a tap drill
machine or a manual tap handle.

#20. Stay Bolt Tap

A stay bolt tap is a type of thread tap, roughly 15–20 inches long that is designed to cut threads in drilled
holes for the threaded machine screws or threaded bolts to be screwed in.
Stay bolt taps were commonly used in the application of locomotive boilers, predominantly in the repair
and installation of fireboxes in steam locomotives.

The distinct feature of this thread tap is that it threads holes that match the diameter of a stay bolt nut.

#21. Bent Shank Tap

A bent shank tap is one option for thread tapping, whereby threads are cut into a material. This form of
tap is used with automatic tapping machines that release nuts through the shank.

In comparison to other thread taps, a bent shank tap has the distinct feature of a bent handle extending
from the tang.

This enables the tap to continuously tap, without the need to stop the drilling machine at different
intervals.

#22. Form or Roll Taps (Thread Forming Taps)

Thread Forming taps don’t cut threads at all. Instead they cold form. Threads made this way are often
called “rolled” threads.

With this process, the metal is pushed out of the way and compressed into position rather than being cut.
There are no chips to remove.

As a result, the taps themselves are less likely to break and the threads they make are stronger. If your
application allows Form Taps, they are generally the best thing going for those reasons.

Form Taps do require different feeds and speeds and they require a different starting hole size, so be
aware of that before using one.
While many believe they’re only good for soft materials like aluminum, they can actually be used on
materials up to a hardness of 36 HRC, which is about 340 BHN. That covers a surprisingly wide range of
materials including a lot of steels.

I will almost always choose a Form Tap over a Cutting Tap out of the available types of taps if the
material isn’t too hard for thread forming.

Article 9

Types of Thread Taps Used in CNC Machining

A thread tap’s construction can provide advantages depending on your project. Different taps may be
appropriate depending on some of the following project specifications:

● Hole type: Your CNC tapping capabilities will depend on whether the hole you’re threading is a
blind or through hole. Blind holes extend to a specific depth without breaking through the other
side of a material, whereas through holes breach the other side. The shape of your thread tap will
need to accommodate the hole type to prevent breakage.
● Fluting needs: Many thread taps have channels — known as flutes — cut into the body to guide
chips away from the tapping site. Different flute types allow taps to either push chips ahead of the
tool or draw them up and away from the tool. These fluting types can be valuable, depending on
whether you’re tapping a blind or through hole.
● Material: The materials used in tapping will make a difference in the type of thread tap you
choose. For example, a material’s hardness may warrant a stronger carbide tap rather than
standard steel. The way the material forms chips is also important. When combined with certain
taps, some materials form short chips, and others create spiraled chips. The direction your tap
pushes a certain kind of chip can either work for or against your tapping process.

With these considerations in mind, let’s examine some common tap types, as well as their uses and
benefits.

1. Straight Flute/Hand Taps

A straight flute or hand tap is one of the most basic taps available. This thread tap gets its name from the
four straight channels that run along the body to handle chips. A straight flute or hand tap can be used
with a machine or powered by hand, which gives it increased versatility. In addition, this tap type works
well with through holes or blind holes.

Some of the strengths of a straight flute or hand tap include:

 ● Its one-size-fits-all nature may decrease the number of tools you need.
● It is well suited for materials like cast iron that create short chips.
● It can transition from a machine to a tap wrench depending on your needs.

2. Spiral Flute Taps

Spiral flute taps differ from straight flute taps due to their flute construction. As the name suggests, a
spiral flute tap utilizes channels that spiral around the tap body in a helical form. This structure helps to
guide chips upwards and away from the tap site, which is especially helpful when tapping a blind hole.

If you use a thread tap that pushes chips into the bottom of a blind hole, you could risk breaking or
damaging the tap when you reach the bottom. Spiral flute taps mitigate this issue by evacuating the chips
efficiently. You may want to differentiate your spiral flute tap further by choosing a spiral degree that
aligns with the material you’re tapping:

● A 5-to-20-degree spiral: A low spiral degree generates slow spirals. This method does not
impede the cutting edge, which is best for tough materials like titanium, nickel or stainless alloys.
● A 25-to-35-degree spiral: This configuration works well for free machining, leaded or low steels,
as well as free-machining brass and bronze.
● A 38-to-42-degree spiral: This degree works well with materials that form relatively tight chips,
such as free machining stainless steel or medium to high carbon steels.
● A 45-degree spiral or higher: Spiral taps with angles of 45 degrees or higher produce a fast
spiral. This configuration works well for ductile materials like copper or aluminum.

In general, some of the strengths of a spiral flute tap include:

● It prevents chips from congregating at the bottom of a blind hole.

● It may take less effort to tap.
● It makes it easier to restart tapping when working with a hole that’s interrupted by another feature.

3. Spiral Point Taps

A spiral point tap utilizes a small but important variation on the straight flute tap. Spiral point taps have an
angled point that helps direct chips out in front of the tool during tapping. Given this construction, spiral
point tap capabilities encompass both through holes and blind holes with enough room to accommodate
chips.

Many of the spiral point tap’s strengths stem from its shallow flute design, including:

● Increased cross-sectional areas

 ● Greater tapping strength with less tapping power required
● Capacity for increased tapping speeds

4. Pipe Taps

A pipe tap has a more narrow application centered around creating pipe threads. This tool is used to cut
the threads in a portion of a pipe fitting or part that will be paired with the portion of an adjoining pipe.
Because of this use, pipe taps tend to have several straight flutes and require more force to use.

You may use a type of pipe tap that differs from standard construction based on your project:

● Spiral flute pipe taps: A spiral flute pipe tap combines the helical channels of a spiral flute tap
with the standard pipe tap structure. This tool draws chips away from the tapping hole when they
may cause issues otherwise.
● Interrupted thread pipe taps: This type of pipe tap has a tooth removed on each cutting edge to
increase chip flow and cut down on tapping friction. Interrupted pipe taps tend to have an odd
number of threads and may be used on a variety of metals.
● Extension pipe taps: Extension pipe taps are designed to drill deep holes in pipes or pipe
fittings. An extension pipe tap may incorporate either a standard or interrupted thread pattern that
helps when tapping difficult areas.
● Thread forming pipe taps: A thread forming pipe tap displaces material rather than cutting it.
This type of tap may be a good choice when working with pipes made of soft metal, steel, copper,
aluminum or brass.

A pipe tap’s key strength is that, when used properly, it can create pressure-tight pipe joints.

5. Thread Forming Taps

Thread forming taps stand out from other tap types because they produce threads differently. Most taps
utilize cutting edges to shave away material and create a thread. While this is effective, it makes
inconvenient chips that can impede the tapping process. Instead of cutting, a thread forming tap displaces
material during tapping.

The thread forming method offers a variety of advantages, including:

● Strength: Formed threads are stronger than cut threads.

● Convenience: Thread forming taps do not produce chips, which is helpful for blind holes.
● Longevity: Thread forming taps may be less likely to break or wear down.
● Efficiency: Thread forming taps may run at faster speeds than cutting taps.
Because of their unique functionality, thread forming taps are best suited for somewhat malleable
materials, such as:

● Aluminum
● Soft steels
● Brass
● Lead
● Copper
● Zinc
● Other medium alloys

An important consideration for thread forming taps is lubrication. The thread forming method generates
increased friction, which can hinder a successful thread. For this reason, most thread forming taps include
grooves or channels that help transport lubricant to the front of the tap. A dedicated tapping or extrusion
fluid may support the best results when using this type of tool.

6. Combined Drill and Tap

As its name suggests, a combined drill and tap can bore and thread a hole in one pass. A combined drill
and tap typically features a drill bit at the tip followed by a spiral fluted tap. This tool is designed so the
drill portion of the tap breaks through the material before the threading section begins.

A combined drill and tap is recommended for through holes only and can handle depths of up to twice the
tap’s diameter. This tool may have a variety of applications within the assembly, construction,
maintenance and repair industries.

Some of the strengths of a combined drill and tap include:

● It is self-centering.
● It operates at high speeds.
● It can save time where applicable.

7. Solid Carbide and Carbide Insert Taps

Most thread taps are made from steel, but some use carbide because of the advantages it provides. As a
material, carbide is extra strong and extra efficient. This makes it ideal when tapping more abrasive
substances such as:

● Cast iron
● Cast aluminum
 ● Polymers
● Glass-filled polycarbonates
● Other non-ferrous materials

Carbide taps may come in one of two configurations:

● Solid carbide taps: These taps are completely fashioned from carbide material, which allows for
increased metal removal at high speeds.
● Carbide insert taps: These taps incorporate carbide at the cutting portion of the tool and High
Speed Steel (HSS) in the body. Though not as strong as a solid carbide tap, a carbide insert tap
can be more affordable.

Solid carbide and carbide insert taps are manufactured in many of the tap configurations we’ve covered. If
you need extra strength and durability for your project, you can choose one of the following:

● Carbide straight flute taps

● Carbide spiral point taps
● Carbide pipe taps
● Carbide thread forming taps

Types of Chamfers Used in CNC Machining

A thread tap can be further differentiated by the type of chamfer it has. The term chamfer refers to the
bottom-most section of a tap. Chamfer designs serve two main purposes: to decrease the amount of
force needed to use the tap and to allow the cutting teeth to make continually deeper cuts.

Manufacturers use varying chamfer angles and lengths depending on a thread tap’s purpose. When
choosing a chamfer type, your primary consideration should be the type of hole you’re tapping and its
depth. There are three main chamfer types you may encounter in CNC machining.

1. Taper Taps

A tapered tap has the longest chamfer length — usually about seven to 10 threads long. In general, the
longer a tap’s chamfer, the easier it will be to begin tapping a hole. A tapered chamfer has a slight inward
angle, which makes it easier to align the tap within your hole.

Because tapered taps don’t have fully formed threads in the chamfer, they are not ideal to use when
tapping the bottom of a blind hole. Instead, tapered taps work well for through holes or when cutting
threads for the first time. You can typically pair a tapered tap with another chamfer style to get the results
you need.
2. Plug Taps

Plug taps have medium-sized chamfers between three and five threads long with a medium inward angle.
A plug tap’s shallow construction requires more force to start a new thread, which makes it more difficult
to use than a taper tap.

This chamfer style works well when you’re repairing a thread that has already been tapped. It can also
help tap deeper into a hole once you’ve started the hole with a taper tap. If you’re threading a through
hole, a plug tap can be a more effective choice than a taper tap due to its construction.

3. Bottoming Taps

A bottoming tap has the smallest chamfer with just one or two threads. This chamfer type has a sharp
inward angle, which makes it ideal for cutting threads to the bottom of a blind hole. Because a bottoming
chamfer is so short, it’s extremely difficult to use when beginning a new thread. Bottoming taps are ideal
to use after you’ve tapped a hole with a taper or plug tap.

Forum

Hand Tapping

Hand taps come in three basic configurations -Taper, Plug and Bottoming.

TAPER taps have the first 7 – 10 threads at the tip ground flatter than the main body of the tap to enable
easy starting of the threads in the hole. Sometimes called a starter tap, taper taps can be be used to start
the thread in a blind hole for another tap to finish or used to cut threads all the way on a through hole.

PLUG taps are like taper taps in that they have tapered threads at the starting end of the tap, the
difference is there are fewer of them, usually the first 3-5 threads, so you get to cutting a full thread
sooner. Although not as easy to start as a taper tap, they can be used to start a thread. If you can only
buy one type of tap, and you’re a patient user, plug taps can be a good choice because they are still easy
to start, but they can also form complete threads deeper into a blind hole than a taper tap.

BOTTOMING taps have no ground threads at the starting end and are generally used after, and in
conjunction with a taper or plug tap. Bottom taps can cut threads to the bottom of blind holes although
they do not do well at starting threads.

The pointed style is usually used as a starter tap. I usually use the flatter style to clean threads. There is
also one called the bottom tap, its cutting edges are closer the end of the tap. The end is more square
and not as tappered as the flat style.
Taper taps are for threw holes

Plug Taps are for blind holes

Bottoming taps are for finishing up the last few threads not cut from the plug tap.

Pointed taps, like stated are for starting or through holes. Flat bottom taps are for blind holes, or holes
that do not goo through the part. Once you get into larger sizes though, some may look like a bottom tap
but are in actuality a starter tap. The larger ones just don't need the point on it.

Another thing about taps, stay away from 4 flutes. More trouble than what they are worth due to not
having enough chip clearance. The best bet for home use, is get two or three flute Gun Taps. I think the
three flute gun taps start at either 5/16" or 3/8" in size. Most small 4 flutes, you'll snap them off and they
are a real bitch to get out. I've had to remove hundreds over the years for production departments. And if
you bind a tap or hear a snap while it's in the hole, good luck on getting one out. They make "tap
extractors" but I have never had any luck with them. When you bind and snap a tap, it's stronger than the
tap extractor anyways.

And never use a rusty tap. 90% of the time it's dull from rust, or it's an older tap that has been laying
around after being used quite a few times. Taps are cheap until you get into the larger sizes. Once you
get a tap, don't let them bang around one another and don't loan any out, so you'll always know what you
have.

Also, ! some of the 4 flute and spiral flute taps are made of Powdered metal, so TREAD LIGHTLY if you
end up having to try to hand tap something with them .

Spiral point taps are for best for through holes and shoot the chips ahead of the tap. Apparently these are
gun taps, altho I was never taught that way.

Spiral flute taps are better for blind holes and feed the chips back out towards you, much like a drill bit.
These are probably my favorite but are more expensive. I once bought a no-name import 8-32 that did
nothing but strip the hole, so now I only buy quality taps, especially in spiral flute.

For general, all-around use I prefer hand taps (which might be the 4 flutes Kevin refers to?). I've
personally had no problems with them over the years, you just gotta use the right technique of back and
forth to break your chip. Hand taps pretty much don't feed the chips one way or another, which sounds
like a bad idea but works out fine in practice.

Your Craftsman link looks like a basic hand tap to me. The Grainger link specifies it's a gun tap, thus
spiral point.
Spiral point taps are for best for through holes and shoot the chips ahead of the tap. Apparently these are
gun taps, altho I was never taught that way.

Spiral flute taps are better for blind holes and feed the chips back out towards you, much like a drill bit.
These are probably my favorite but are more expensive. I once bought a no-name import 8-32 that did
nothing but strip the hole, so now I only buy quality taps, especially in spiral flute.

For general, all-around use I prefer hand taps (which might be the 4 flutes Kevin refers to?). I've
personally had no problems with them over the years, you just gotta use the right technique of back and
forth to break your chip. Hand taps pretty much don't feed the chips one way or another, which sounds
like a bad idea but works out fine in practice.

^^^ This. I always recommend against spiral point taps for home use as they can quickly get you into
trouble on blind holes. Learn to use a regular 4 flute hand tap well as that is what you will likely be buying
upon the occasion of needing a special thread.

I believe calling spiral point taps "gun taps" is a relatively recent misnomer. I was always taught that gun
taps are like gun drills - for tapping/drilling DEEP holes.

While we're here;

Can someone clarify the different between a thread-chasing tap and a cutting tap?

I was under the impression a thread-chaser was less likely to over-size a given thread.

There are 4 different thread tolerances, that is the easiest way to put it. They are each classified as a
"Class".

Basically,the only difference between plug and taper type taps is the number of threads that are ground

away or chamfered at the very end. The taper type is the easiest to start off square,the plug type is the

most common. Bottoming type taps are used for tapping closer to the bottom of a blind hole,meaning

there is not a hole all the way through the part you are tapping. Other than different H limits,which is the

amount of play the cutting edges of the tap allow inside the hole,there is practically no difference between

taps used for cutting metal or wood threads. For example,an H2 tap for 5/16-18 threads is the basic

diameter of the fastener to be used,in this case .3125,plus .0005-.001. In just about all cases for fasteners
under 1 1/2,an H3 tap is most common. For applications such as large wood-screw/Acme type joint

pins,H0 taps are available,this is a super tight,almost interference fit. Thread forming taps work a little

differently,it pushes the material out of the way and forms it to the new shape rather than cutting the

material away,thread forming taps are not of much use in cuemaking as far as I know. Tommy D.

What are these kind of taps called?

Quote

Post

by ecdez » Mon Dec 24, 2018 7:13 pm

See the picture below. The add lists them as this

Thread Limit H3, 3 Flute, Oxide Finish Vanadium High Speed Steel Spiral Flute Tap
Modified Bottoming Chamfer, Right Hand Thread, Right Hand Flute, 2-1/2 OAL, 6.477mm Diam, Class 3B

No problem. Question is, the threads appear to taper off after the 4th or 5th thread in. Is there a specific
name for that feature? All the other nomenclature in the listing seems to reference everything else. I'm
having some trouble tapping 1" thick stock on the CNC with every other tap I can get my hands on. I think
the coolant (mist) can't get down toward the bottom of the hole. I'm also thinking having only a few full
size cutting threads will help keep things cool. Sure this is the one I can try buy knowing what that feature
is called will help me locate them in the future or from another source.

Thanks in avance!

Link to catalog listing.

https://www.mscdirect.com/product/details/62666789
Top
 choprboy

Posts: 322

Joined: Sat Oct 29, 2011 11:23 pm

Re: What are these kind of taps called?

Quote

Post

by choprboy » Mon Dec 24, 2018 8:14 pm

Well... the are 3 basic tap thread taper/chamfer: Taper, Plug, and Bottoming. The more taper the easier it
is to cut (less cutting force on each tooth), but the longer it takes and less efficient the cut.The tap in your
description is a bottoming tap. The number threads in the taper varies a bit manufacturer, but tend to
roughly be:
Taper - 7-10 threads - for thru-hole hand tapping
Plug - 3-6 threads (normally around 5) - for machine thru-hole tapping (though I normally hand tap with
one)
Bottoming - 1-3 threads (normally about 2) - for machine tapping to the bottom of blind holes (possibly
with a plug tap partially run to start)

If your are thru-hole tapping on a CNC, you probably want to use a spiral flute plug tap.
Top

John Hasler

Posts: 1852

Joined: Tue Dec 06, 2016 4:05 pm

Location: Elmwood, Wisconsin

Re: What are these kind of taps called?

Quote

Post

by John Hasler » Mon Dec 24, 2018 8:31 pm

For through-hole tapping you want a spiral point tap, also called a gun tap. It shoots the chips forward out
through open hole. Spiral (helical, actually) flute taps are most suitable for blind holes because they pull
the chips up and out.
Top

johnfreese

Posts: 219

Joined: Thu Jan 21, 2016 2:10 am

Re: What are these kind of taps called?

Quote

Post

by johnfreese » Mon Dec 24, 2018 11:26 pm

Most of my spiral flute taps have dimensions similar to a hand tap. I see the type pictured here in
catalogs. They seem to be designed for machine tapping in a production environment. They have a short
threaded portion with a reduced shank above the threads. I have no idea what the benefit of that
configuration is. I hope there is a member that could educate me regarding that tap design.
Top

neanderman

Posts: 932

Joined: Mon Jan 09, 2012 7:15 pm

Location: Cincinnati, Ohio, USA

Re: What are these kind of taps called?

Quote

Post
by neanderman » Tue Dec 25, 2018 2:15 am

johnfreese wrote: ↑

Mon Dec 24, 2018 11:26 pm

I hope there is a member that could educate me regarding that tap design.

Second that!

Ed

LeBlond Dual Drive, 15x30

US-Burke Millrite MVI

Atlas 618

Files, snips and cold chisels

Proud denizen of the former "Machine Tool Capitol of the World", I know a little bit about a lot of things.
Top

ecdez

Posts: 30

Joined: Mon Mar 12, 2012 4:14 pm

Re: What are these kind of taps called?

Quote

Post

by ecdez » Tue Dec 25, 2018 5:07 am

Thanks for the responses thus far. I understand that it's a bottoming tap both by the general shape and by
the number of tapered threads leading in. It's the tapered threads above the threaded portion that I
thought would have special name and knowing that name might make it easier to locate. Perhaps I'm
wrong.
I've used both a sprial flute and a gun tap and either will work fine for tapping 1/2" material but when I get
to the 1" stuff they always break 2-3 holes into the project. EVERY TIME!!

This special tap may not be the solution to the problem but it's worth a try. That is, unless someone can
offer another solution I hadn't thought of.

Thanks!
Top

Harold_V

Posts: 20499

Joined: Fri Dec 20, 2002 11:02 pm

Location: Onalaska, WA USA

Re: What are these kind of taps called?

Quote

Post

by Harold_V » Tue Dec 25, 2018 5:39 am

ecdez wrote: ↑

Tue Dec 25, 2018 5:07 am

I've used both a sprial flute and a gun tap and either will work fine for tapping 1/2" material but when I
get to the 1" stuff they always break 2-3 holes into the project. EVERY TIME!!

How do you drive the tap? If you're tapping by hand, or without some means to register the tap so it's
dead vertical with the hole, yeah, you can expect breakage. A tap, once started crooked, suffers because
it doesn't have the ability to straighten as it progresses in the hole. That condition is forgiving to some
degree in thin material, but a death sentence in thick stuff. It typically leads to a broken tap as the chip
load becomes so great on one side that the tap deflects until it breaks. Needless to say, taps, which are in
excess of 60 Rc, don't bend.

Strange as it may sound, if you hope to tap without breaking taps, power drive them, but make damned
sure you can stop the tap at the appropriate time, and that it is well lubricated with the proper lubrication
for the material being tapped. The use of a tapping head is strongly advised, assuming you can justify
one. They're not cheap. Using a drill chuck for tapping can be acceptable, although if the threads are
inspected, pretty good chance they will be oversized. Drill chucks rarely run true enough to yield a tight
thread. If nothing else, they'll usually start bell-mouthed.

The other concern might be if you're trying to power tap using a hand tap. If they're not reversed regularly,
which breaks the chip and, hopefully, allows it to drop from the flute, the flutes will fill to the point of
wedging the tap in the generated thread. That is usually followed by breakage. Don't power tap with a
hand tap unless the material is quite thin.

Unfortunately for me, I left the machining field way back in '83, and made no attempt to stay current with
technology. While I am aware of the grind of the "new" style taps, I am not aware of the benefits they
offer, so I can't contribute anything to that conversation. Such taps were not on the market when I was
actively machining.

Wise people talk because they have something to say. Fools talk because they have to say something.
Top

ecdez

Posts: 30

Joined: Mon Mar 12, 2012 4:14 pm

Re: What are these kind of taps called?

Quote

Post

by ecdez » Tue Dec 25, 2018 8:11 am

I'm tapping on a CNC mill with a tapping head. It's a tension/compression style so the motor reverses to
get it out.
Top
 John Hasler

Posts: 1852

Joined: Tue Dec 06, 2016 4:05 pm

Location: Elmwood, Wisconsin

Re: What are these kind of taps called?

Quote

Post

by John Hasler » Tue Dec 25, 2018 9:06 am

Here is a document that may be relevant:

https://www.natool.com/sites/default/fi ... 05-106.pdf

I think that "back taper" may be the term you are looking for.
Top

ecdez

Posts: 30

Joined: Mon Mar 12, 2012 4:14 pm

Re: What are these kind of taps called?

Quote

Post

by ecdez » Tue Dec 25, 2018 9:18 am

Could be! I didn't realize that it had a purpose. It says it gives a slight radial relief on the thread.
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 GlennW

Posts: 7353

Joined: Sun Apr 15, 2007 9:23 am

Location: Florida

Re: What are these kind of taps called?

Quote

Post

by GlennW » Tue Dec 25, 2018 1:37 pm

If you are tapping 1" deep, your mist coolant is most likely the problem, unless you are trying to tap blind
holes that deep using spiral point or hand taps.

You need flood coolant or a good tapping fluid.

Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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Harold_V

Posts: 20499

Joined: Fri Dec 20, 2002 11:02 pm

Location: Onalaska, WA USA

Re: What are these kind of taps called?

Quote
Post

by Harold_V » Tue Dec 25, 2018 5:03 pm

ecdez wrote: ↑

Tue Dec 25, 2018 9:18 am

Could be! I didn't realize that it had a purpose. It says it gives a slight radial relief on the thread.

Unbeknownst to many, many cutting tools have that same feature. The periphery of drills and reamers get
smaller towards the shank, as an example. That's to lower friction of the tool in the hole. Woodruff cutters
are hollow ground on the sides, for the same reason. It's very important that cutting tools make contact
with material ONLY where they cut.