Cut t i n g

Cutting Tool Applications

Tool o n s
p p l i c a t i
A
By Geor
ge Schneide
r, Jr. CMfgE
 Chapter 6
Upcoming Chapters

Metal Removal
Cutting-Tool Materials
Metal Removal Methods
Machinability of Metals

Single Point Machining

Turning Tools and Operations
Turning Methods and Machines
Grooving and Threading
Shaping and Planing
Grooving
& Threading
Hole Making Processes
Drills and Drilling Operations
Drilling Methods and Machines
Boring Operations and Machines
Reaming and Tapping

Multi Point Machining

Milling Cutters and Operations
Milling Methods and Machines
Broaches and Broaching 6.1 Introduction
Saws and Sawing Grooving and threading are both single point machining operations performed on lathes,
automatic lathes, or machining centers. Outside diameter (OD) and face grooving oper-
Abrasive Processes ations are shown in Figures 6.1a and 6.1b respectively. Internal threading or tapping will
Grinding Wheels and Operations be discussed in a later chapter.
Grinding Methods and Machines
Lapping and Honing 6.2 Grooving or Recessing Operations
Grooving or recessing operations, sometimes also called necking operations, are often
done on workpiece shoulders to ensure the correct fit for mating parts (Fig. 6.2a) When
a thread is required to run the full length of the part to a shoulder, a groove is usually
machined to allow full travel of the nut. (Fig. 6.2b) Grooving the workpiece prior to cylin-
drical grinding operations allows the grinding wheel to completely grind the workpiece
without touching the shoulder.(Fig. 6.2c)

George Schneider, Jr. CMfgE

Professor Emeritus
Engineering Technology
Lawrence Technological University
Former Chairman
Detroit Chapter ONE
Society of Manufacturing Engineers
Former President
International Excutive Board
Society of Carbide & Tool Engineers
Lawrence Tech. Univ.: http://www.ltu.edu
Prentice Hall: http://www.prenhall.com
FIGURE 6.1a: Outside diameter (OD) FIGURE 6.1b: Face Grooving operation
grooving operation (Courtesy: Valenite Inc.) (Courtesy: Valenite Inc.)

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 Chap. 6: Grooving & Threading
the part is to be heat treated.
Grinding
wheel
6.3 Parting or Cut Off Operations
In parting operations the workpiece
rotates while the tool carries out a radi-
al feed movement. As with face turn-
ing, the tool is fed from the periphery of
the workpiece towards the center and
(c) the cutting speed is reduced to zero - but
(a) here the similarities end. A typical part-
Nut Groove for
grinding relief ing operation is shown in Figure 6.4.
Groove for Thread As the cutting tool progresses
mating parts towards the center, another factor takes
effect. As the diameter of the workpiece
is reduced, the radial cutting force will
cause the material to break before the
insert has cut through it. This results in
Groove to allow (b) a pip or burr being formed in the center
full travel of nut
of the workpiece. This pip will always
FIGURE 6.2: Grooving operations to provide clearance for a) mating parts;
be there after parting, but its size can be
b) full travel of nut; c) grinding relief. reduced by choosing the correct insert
geometry, feed rate, and support for the
sagging workpiece.
6.2.1 Face Grooving can be machined, and the diameter mea- In a parting operation, there is mater-
With face grooving operations the tool sured to the inside of the blade deter- ial on both sides of the insert. This
is fed axially rather than radially mines the limit for the largest possible means that the tools used are narrow
towards the end surface of the work- groove diameter. and that the length of the toolholder
piece. The tool must be adapted to the increases with an increased diameter.
radial curve of the groove and the blade 6.2.2 Internal Grooving Therefore, stability becomes a critical
is therefore curved. When the machine The main problem with internal groov- factor.
spindle rotates in a counter-clockwise ing is chip evacuation. There is a very Since the size of the tool and tool-
direction, a right-hand version of the high risk of chip jamming which can holder must be optimized to meet
tool is used and a left-hand version is result in tool breakage, especially when requirements, only a small surface is
used when the machine spindle rotates machining small diameters. The chips present for drawing off heat, and there-
clockwise. A face grooving operation is have to be removed from the groove
shown in Figure 6.1b. then change direction 90 degrees and
So that both insert and toolholder fit pass the side of the toolholder to finally
into the groove, both the outer and inner be removed from the hole. Introducing
diameters of the groove must be consid- intermittent feed into the program is the
ered. The diameter measured to the out- best way to obtain short chips. An inter-
side of the blade determines the limit for nal grooving holder with insert is shown
the smallest possible diameter which in Figure 6.3.
Vibration is another common problem
associated with internal grooving.
Stability is related to the overhang, or
how far into the workpiece the groove is
to be machined. The risk of vibration is
reduced by using the largest toolholder
possible. The overhang should not
exceed 2 - 2.5 × the diameter. Internal
grooving is a critical operation and it is
important to choose a tool which opti-
mizes chip evacuation with vibration-
free machining.
Grooving tools are usually ground to
the dimensions and shape required for a
particular job. Most grooving tools are
similar in appearance to the cutoff tool,
except that the corners are carefully
FIGURE 6.3: Internal grooving holder rounded because they reduce the possi- FIGURE 6.4: Parting or cut-off operation
with insert (Courtesy: Valenite Inc.) bility of cracks in the part, especially if (Courtesy: Iscar Metals, Inc.)

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 Chap. 6: Grooving & Threading
causing the results, a maximum deviation in posi-
insert to tioning of only ±.004 inch from the cen-
deflect. ter line is acceptable.
With large As the cutting edge deviates from the
lead angles the center line, the rake angle and the clear-
deflection can ance angle will be changed. This
be so strong change is due to the radius of the work-
that a rounding piece. A clearance angle that is too
of the end sur- small may cause the cutting edge to rub
faces occurs against the workpiece. If the cutting
and results in a edge is positioned too low, the tool will
convex or a leave material in the center and a pip
concave end will be formed.
surface. A
reduced lead 6.3.4 Operational Stability
FIGURE 6.5: Chip control grooving and parting inserts (Courtesy: angle produces With conventional external turning the
Iscar Metals, Inc.)
larger radial tool overhang is not affected by the
fore cutting fluid becomes important. cutting forces but this can cause vibra- length of the workpiece. The size of the
Unfortunately, because of the space tion problems especially when small toolholder can be chosen so that it with-
restrictions, the supply of cutting fluid diameters are machined. In grooving stands the stresses which arise during
is obstructed by the chips. Since chip operations a radial displacement of the the operation. However, with parting
evacuation is difficult and there is noth- insert results in an inaccurate groove and grooving operations, consideration
ing against which to break the chips, the depth. must be given to the depth of insertion
side surfaces can easily be damaged and the width of the groove, which
during the operation. 6.3.2 Chip Control means that stability must often be com-
With parting and grooving operations, promised to meet specifications.
6.3.1 Insert Geometry the insert has machined surfaces on both To obtain the best possible stability,
At the beginning of a cut the insert will sides of the feed direction. Therefore the overhang should be as small as pos-
work at a relatively high cutting the chips must be formed in such a way sible, so a holder for the shortest possi-
speed,and must be able to resist plastic that they are narrower than the groove, ble insertion depth should be chosen.
deformation. The speed reduces as the otherwise the surfaces can be damaged. Wider inserts can be used in order to
tool approaches the center, at which In addition, the chips must be formed in improve the stability, but more material
point it becomes zero. such a way that they can be evacuated is wasted in the form of chips. This can
Modern machines can be pro- from the groove without disrupting the be expensive with large batches and
grammed so that the spindle speed is machining with long, unwieldy chip when machining expensive materials.
automatically increased towards the coils. Therefore the chips are formed in Vibration can also arise as a result of
center, so that the cutting speed is kept two directions: bent across their width the deflection of the workpiece. The
constant. But the maximum spindle and rolled together longitudinally to closer the chuck is to the parting posi-
speed of the machine will be reached form a spiral spring-shaped chip. tion, the lower the effect of the stresses
before the tool reaches the center, and Figure 6.5 shows three chip control and the deflection of the workpiece will
this could result in insert edge build-up. inserts. be. Therefore, if a workpiece has a ten-
Therefore a tough tool material will be In order to produce this ideal chip dency to vibrate, the machining should
needed to resist edge build-up as the shape the insert is usually provided with be done as close to the chuck as possi-
tool gets closer to the center. a chip former as shown in Figure 6.5, ble.
Advanced insert geometries are nec- which takes into account both the The risk of vibration must be kept to
essary for performing parting and machining conditions and the work- a minimum in order to obtain acceptable
grooving operations in a satisfactory piece material. It is shaped in such a results in quality and tool life. In addi-
way. A positive rake insert gives lower way as to form a bank which the chips tion to choosing the best tool and most
cutting forces and thus lower pressure can climb against during machining. stable set up, the cutting data must be
on the workpiece, and this will reduce After a number of revolutions the chips adapted to minimize the tendency of the
the size of the pip. However, a large will break automatically. The diameter tool and workpiece to vibrate.
positive rake angle means a weaker cut- of the spiral spring chips is influenced
ting edge. by the width of the insert, the height of 6.3.5 Toolholder and Insert
The insert can have various lead the bank, the feed, and the workpiece Selection
angles. On straight or neutral inserts the material. Modern parting and grooving cutting
lead angle is zero. This design provides tools consist of a toolholder and an
a stronger cutting edge and a better sur- 6.3.3 Tool Positioning indexable insert developed specifically
face finish, while maintaining closer As with conventional turning, it is for a particular operation. The majority
tolerances with respect to perpendicular important that the cutting edge be posi- of inserts produced over the last decade
alignment. With an increased lead tioned on the same level as the center were designed to work with the SELF-
angle the axial cutting force increases, line. In order to achieve satisfactory GRIP concept. This clamping method

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 Chap. 6: Grooving & Threading
when conditions are that must be met.
stable and higher Some important hints for applying
cutting speeds are grooving and parting tools:
required, the choice • always use plenty of cutting fluid.
narrows to titanium- • set the center-height of the cutting
aluminum-nitride edge accurately
coatings applied by • make sure toolholder/blade is accu-
the PVD process, or rately positioned at 90 degrees to the
the newer medium- workpiece axis.
temperature CVD • use toolholder with the shortest possi-
process. The reason ble length of insertion for the operation
is because TiAlN in question.
FIGURE 6.6: Self-grip tool holders use no external screw to acts as a good heat • select the largest shank/bar for the tool
hold the insert ( Courtesy: Iscar Metals, Inc.) barrier for the car- • adapt the cutting speed to avoid vibra-
bide substrate and tions
incorporates no external screws or can handle elevated temperatures. • reduce the feed rate for the final part
levers to hold the insert in place as Figure 6.8 shows a variety or grooving when parting-off bar material/compo-
shown in Figure 6.6. Instead, it relies and parting tool holders with coated nents.
on the rotation of the part and tool pres- indexable inserts.. • for axial grooving, make the first
sure to keep the insert seated in a plunging cut at the largest diameter, far-
wedge-style pocket. The inserts 6.4 Grooving and Parting thest out on the face, to minimize the
designed for this type of holder are usu- Recommendations risk of chip jamming
ally single ended and their geometry The ability to efficiently cut off work- • use the smallest possible lead angle for
permits unlimited depth of cut. pieces and blanks in lathes has always avoiding pips/burrs in parting-off
With double-ended inserts, also been important in getting the job com- • when possible, use a toolholder with a
known as “dogbones”, the depth of cut pleted. Even in special purpose cutoff strengthening radius between shank and
is limited by the second cutting edge as machines, a good parting tool is at the blade.
shown in Figure 6.7. Dogbone inserts heart of the operation. Today’s modern
traditionally can only cut as deep as the indexable insert parting and grooving 6.5 Screw Threads and Threading
overall length of the insert. Once the tools provide the same productivity lev- The screw thread dates back to 250 B.C,
depth is reached, the trailing edge will els as modern turning tools. when it was invented by Archimedes.
begin to rub inside the groove that the In parting operations, the objective is For centuries wooden screws, hand-
tool is creating. In addition, dogbone to separate one part of the workpiece made by skilled craftsmen, were used
inserts usually are secured by a screw- from the other as efficiently and reliably for wine presses and carpenters’ clamps
top clamp, which also limits the depth as possible. In grooving operations, the throughout Europe and Asia. Precision
of cut as again shown in Figure 6.7. principle is the same, although these in screw and thread manufacture did not
Coatings for grooving and parting operations are less sensitive because the come into being until the screwcutting
inserts vary from supplier to supplier. grooves are usually not as deep. In lathe was invented by Henry Maudslay
But titanium carbon nitride applied by grooving, the shape, accuracy and sur- in 1797.
the PVD process has practically become face finish are
the industry standard for lower cutting the main
speeds and tougher applications. And requirements

FIGURE 6.7: Dogbone insert tool holders have limited depth FIGURE 6.8: Various OD and ID grooving holders. (Courtesy:
of cut (Courtesy: Iscar Metals, Inc.) Iscar Metals, Inc.)

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 Chap. 6: Grooving & Threading

Thread culate the dimen- to tighten it. Thread fit is the range of
angle Crest sions correctly. tightness or looseness between external
Screw set nomen- and internal mating threads. Thread
Root clature is shown in series are groups of diameter and pitch
Figure 6.9. combinations that are distinguished
The major from each other by the number of
Major Minor Pitch diameter is the threads per inch applied to a specific
Diameter Diameter Diameter largest diameter of diameter. The two common thread
the screw thread. series used in industry are the coarse
On an external and fine series. specified as UNC and
Single Depth thread it is the out- UNF.
Flanks side diameter; on
Helix angle
Pitch an internal thread it 6.5.2 Unified Thread Form
is the diameter at The Unified screw thread has a 60
FIGURE 6.9: Screw Thread Nomenclature. the bottom or root degree thread angle with a rounded root
of the thread. and a crest that is flat or rounded. As
In the early 1800’s, Maudslay also The minor diameter is the smallest mentioned earlier, this is the principal
began to study the production of uni- diameter of a screw thread. On an exter- thread form used for screw thread fas-
form and accurate screw threads. Until nal thread, the minor diameter is at the teners used in the United States. The
then no two screws were alike; manu- bottom of the thread; on an internal Unified screw thread system includes
facturers made as many threads per inch thread the minor diameter is the diame- six main thread series:
on bolts and nuts as suited their own ter located at the crest. 1. Unified Coarse (UNC)
needs. For example, one manufacturer The pitch diameter is an imaginary 2. Unified Fine (UNF)
made 10 threads per inch in 1/2 -in. - diameter that passes through the threads 3. Unified Extra-Fine (UNEF)
diameter threaded parts, whereas anoth- at the point where the widths of the 4. Unified 8-Pitch (8 UN)
er made 12 threads, and so forth. groove and the thread are equal. The 5. Unified 12-Pitch (12 UN)
During this period the need for thread pitch diameter is the most important 6. Unified 16-Pitch (16 UN)
standards became acute. dimension on a screw thread; it is the The coarse-thread series (UNC) is
Despite many attempts at standard- basis from which all thread measure- one of the more commonly used series
ization, it was not until World War I that ments are taken. on nuts, bolts, and screws. It is used
thread standards were developed. The The root is the bottom surface con- when lower-tensile-strength materials
thread profile was designated the necting two sides of a thread. The crest (aluminum, cast iron, brass, plastics,
American National thread form and is the top surface connecting two sides etc.) require threaded parts. Coarse
was the principal type of thread manu- of a thread. Pitch is the linear distance threads have a greater depth of thread
factured in the United States until World from corresponding points on adjacent and are required on these types of mate-
War II. threads. The pitch is equal to 1 divided rials to prevent stripping the internal
During World War II the United by the total number of threads per inch threads.
States manufactured military equipment (P=1/[no.threads/in.]). A screw having a The fine-thread series (UNF) is used
that used the American National thread single lead with 16 threads per inch has on higher-tensile-strength materials
form, which presented interchangeabili- a pitch equal to 1/16 in., commonly where coarse threads are not required.
ty problems with machinery made in referred to as a “16-pitch thread”. Because they have more threads per
Canada and Great Britain. Not until The lead is the axial distance a inch, they are also used where maxi-
after World War II in 1948, did these threaded part advances in one complete mum length of engagement between the
countries agree upon a Unified thread rotation. On a single lead threaded part, external and internal threads is needed.
form to provide interchangeability of the lead is equal to the pitch. The extra-fine thread series
threaded parts.The Unified thread form The depth is the distance, measured (UNEF) is used when even greater
is essentially the same as the old radially, between the crest and the root lengths of engagement are required in
American National, except that it has a of a thread. This distance is often called thinner materials. Eight, 12 and 16-
rounded root and either a rounded or flat the depth of thread. pitch threads are used on larger-diame-
crest. The Unified thread form is The flank is the side of the thread. ter threads for special applications. The
mechanically interchangeable with the Thread angle is the angle between the 8-pitch is generally regarded as a coarse
former American National threads of flanks of the thread. For example, thread for larger diameters, 12 pitch is
the same diameter and pitch. Today it is Unified and Metric screw threads have a the fine series, and 16 is the extra-fine
the principal thread form manufactured thread angle of 60 degrees. Helix is the thread used on the larger-diameter
and used by the United States. curved groove formed around a cylinder threads.
or inside a hole. The relationship between the pitch
6.5.1 Screw Thread Nomenclature A right-handed thread is a screw diameter or major diameter deter-
Screw threads have many dimensions. thread that requires right-hand or clock- mines the helix angle of that thread. For
It is important in modern manufacturing wise rotation to tighten it. A left-hand- example, a 12-pitch (12 UN) thread
to have a working knowledge of screw ed thread is a screw thread that requires with a 1.250-in. major diameter will
thread terminology to identify and cal- left-hand or counterclockwise rotation have a greater helix angle than a 12-

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 Chap. 6: Grooving & Threading

FIGURE 6.11: Various grooving and threading inserts (Courtesy: Valenite

Inc.)

FIGURE 6.10: Grooving and threading tool holders clearance on all diameters to the workpiece rotation. The point gen-
(Courtesy: Valenite Inc.) provide for free movement. erates the typical spiral groove that
Class 2G threads are used on makes up the screw thread with a cer-
pitch thread with a 2.0-in. major diame- most assemblies. Classes 3G and 4G tain pitch. Basically, threading is a
ter. Generally speaking, the lower the are used when less backlash or loose- well-coordinated turning operation with
helix angle, the greater the tensile stress ness is permissible, such as on the lead a form-tool. During the feed passes, the
applied to the bolt for a given torque screw of a lathe or the table screw of a tool is moved longitudinally along the
applied to the nut. The fastener with a milling machine. workpiece and then withdrawn and
lower helix angle will also resist vibra- moved back to the starting position for
tion and loosening more effectively. 6.5.4 Tapered Pipe Threads the next pass along the same thread
A grooving and threading holder is Pipe threads, usually designated groove.
shown in Figure 6.10 and various NPT (National Pipe Taper) are tapered The feed rate is a key factor that has
grooving and threading inserts are threads used for sealing threaded joints to coincide with the pitch of the thread.
shown in Figure 6.11 such as water and air pipes. Most pipe The coordination is obtained by various
threads have a slight taper (3/4-in./ft) means, depending on the type of
6.5.3 Acme Screw Threads and are cut using special pipe taps and machine; lead screw, cam or numerical
Acme screw threads are manufactured dies. Pipe threads can also be machined control (usually handled as a sub-rou-
for assemblies that require the carrying using the taper attachment on an engine tine in CNC). The shape of the groove
of heavy loads. They are used for trans- lathe. produced is determined by the shape of
mitting motion in all types of machine
tools, jacks, large C-clamps, and vises. 6.6 Thread Turning
The Acme thread form has a 29 degree Development of threading tools has
thread angle and a large flat at the crest
come a long way since the days of
and root (see Fig. 6.12). high speed tool-bits and tips ground to
Acme screw threads were designed to shape, which were then slowly fed
replace the Square thread, which is dif-along by the lathe lead screw. Most of
ficult to manufacture. today’s threading is performed by
There are three classes of Acme indexable insert tools as part of a very
threads (2G, 3G, and 4G), each having rapid CNC process. What used to be a
relatively difficult and time-
Pitch consuming part of machining is
now standard procedure as with
Flat any other operation. A typical
(crest)
part that requires a thread is
routinely machined with fixed
29° cycles of numerical control and
Depth a variety of other machine
Flat mechanisms and using tools
(root) which have the right thread
shape. An ID and OD threading
operation with coated indexable
inserts is shown in Figure 6.13.
The principle of single point FIGURE 6.13: OD and ID threading
FIGURE 6.12: General purpose Acme screw
thread thread cutting is the feed move- Operation (Courtesy: Sandvik Coromant
ment of the tool in relation to Corp.)

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 Chap. 6: Grooving & Threading
coated inserts allow a wider range of
Cutter Feed direction cutting speeds between the area charac-
terized by built-up edge formation at
lower speeds and plastic deformation at
(a) (b) higher speeds. Threading involves
many short cutting sequences and often
relatively low cutting speeds throughout
machining. Of major importance in
threading is the ability of the cutting
tool to keep the built-up edge tendency
to an absolute minimum, or prevent it
entirely, depending upon the workpiece
Part material. A built-up edge will cause
poor surface finish and eventually lead
FIGURE 6.14: External thread milling with: a) single-row and b) multiple-row
tooth cutter to edge breakdown and tool failure.

the insert point, and the feed rate is con- cutting conditions this order is not criti- 6.7 Thread Milling
siderably higher than for ordinary turn- cal. It is vital, however, that inserts Thread milling has been an established
ing operations. always be used with holders of the same method of manufacturing accurate
The relatively small 60 percent point hand. screw threads for many years. Long
angle of the tool makes the cutting edge screws, such as lead screws on lathes
susceptible to the forces and stresses of 6.6.2 Toolholders and Insert and multiple start threads, are often
metal cutting. To counter this, a long Selection manufactured by milling.
established method has been to use the Compared to conventional turning, the Milling a screw thread is done with
thread depth to determine the cutting tool and machining parameters of either a single- or multiple-lead milling
depth, and to avoid machining in one threading are not so flexible. This is cutter. The rotating cutter is fed into the
pass. Instead, the depth is machined in mainly because the feed is related to the work to the required depth. The work is
several passes. The cutting tool opens pitch, the cutting depth is divided into then rotated and fed longitudinally at a
up the thread groove by cutting deeper passes, and the cutting speed is limited rate that will produce the proper lead on
and deeper, usually by making 5 to 16 because of the pointed cutting edge. the part (Fig. 6.14). Any class of fit or
passes, depending on the thread pitch. Indexable inserts are available for thread form can be manufactured by the
As each pass is made, more and more external and internal threading. The thread milling process.
material is removed per cut as a larger inserts for internal threading
part of the edge is engaged. For this are mirror images of the cor-
reason, the depth of cut is reduced suc- responding external inserts.
cessively as the passes are made. Both external and internal Single-rib wheel
It is best to have radial in-feeds which inserts are available in right
decrease successively as the passes are and left-hand versions. Since
performed. The number of in-feed pass- tolerances and cutting geome-
es must be balanced to provide the edge tries differ between external
with sufficient but not excessive cut into and internal inserts, it is
the workpiece. Too much cutting force important that they should not
with insufficient cutting depth leads to be confused.
premature tool wear.
6.6.3 Coated Threading (a)
6.6.1 Left and Right-Hand Threads Inserts
The difference in direction between left The development within
and right-hand threads does not affect thread turning tools has been Multi-rib
the thread profile; it does, however, considerable during the past wheel
have some effect on the choice and thirty years, since the intro-
combination of tools. The method of duction of the first flat inserts
cutting the thread depends on the work- with a loose chip former
piece design. Working towards the clamped on top of the inserts.
chuck is the most common method, Today’s modern inserts have
even though working away from the done away with most of the
chuck is in many cases also satisfactory. possible problems that can
The advantage in using right-hand arise with conventional (b)
tools for right-hand threads and left- threading inserts. This has
hand tools for left-hand threads, is that made threading more closely FIGURE 6.15: Shown are: a) single and b) multiple
the holder is designed to give maximum resemble a turning operation. rib thread grinding wheels
support to the insert. But under normal The multi-purpose PVD

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 Chap. 6: Grooving & Threading
6.8 Thread Grinding Ground threads are produced by threads are single-or multiple-rib. (Fig.
Grinding a screw thread generally is thread-grinding machines. A thread- 6.15) Single-rib types are used for
done when the hardness of the material grinding machine closely resembles a grinding longer threads and feed longi-
makes cutting a thread with a die or sin- cylindrical grinder in appearance. It tudinally for the required length of
gle point tool impractical. Grinding incorporates a precision lead screw to thread. The multiple-rib type of grind-
threads also results in greater accuracy produce the correct pitch or lead on the ing wheel is generally used for forming
and in superior surface finishes com- threaded part. Thread-grinding short threads. This type of wheel is
pared to what can be achieved with machines also have a means of dressing “plunged” into the workpiece to pro-
other thread-cutting operations. Taps, or truing the cutting periphery of the duce the thread.
thread chasers, thread gages, and grinding wheel so it will produce a pre- Internal threading or tapping will be
micrometer spindles all use ground cise thread form on the part. Grinding discussed in a later chapter as part of
threads. wheels used in producing ground hole-making processes.

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