American System
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ScribdTranslationsAmerican System
Within the regulations for threads are the ANSI, ASTM, ASME, and UST systems.
ANSI System
The American National Standards Institute (ANSI) publishes
standards for large diameter screws, including their dimensions and convention of
names. The ANSI standards include the permissible body diameter, the diameter of the
head, the size of the groove and the length of the thread. ANSI has issued standards for the
screws based on their type and design, and whether they are in metric units or
Americans. Within ANSI regulations, screws are designated by
parameters such as:
Nominal size or base diameter.
2. Number of holes per inch.
3. The length of the product.
4. Step family rings
5. Class assignment.
Because in this nomenclature ANSI has issued standards for screws based on fu
Function and design find different standardized regulations.
The ANSI B1.2 standard for Unified Thread Gages and Calipers
Screws in Inches
This standard provides essential specifications and dimensions for gauges.
used in screw threads in unified inches UN and UNR [only threads
external) thread form, and covers the specifications and dimensions for the
thread gauges and the measuring equipment are also described along with the basic purpose
and the use of each caliber.
The ANSI B1.3M standard for Dimensional Systems of Thread Gages and
Metric Acceptability in Inches,
Define the standard American fasteners of unified threads
built in metric units.
ANSI B18.3 for hexagon socket screws and slotted flat head screws
Avellaneda
It is the standard for hex head screws and slotted head screws.
avellanada. These screw thread measurement systems consist of
Characteristics of fastener threads that should be inspected to establish the
dimensional acceptability of the threads of fasteners in a threaded product and the
calibers used when inspecting those characteristics.
ANSI B18.6.2 is the ANSI standard for flat head slotted screws.
Avellaneda. This standard covers the complete general and dimensional data for
square-headed screws and slotted screws without heads, from their dimensions
general, including their chemical composition, hardness requirements, tension requirements
and its applications.
ANSI B18.11 applies to miniature screws.
They present specifications of miniature threads, including their characteristics.
dimensional, its material (can be made of stainless steel, carbon steel
carbon or alloyed steel, which makes the products capable of withstanding a
decent amount of wear), applications (ranging from use in computers,
electronic cabinets, food machines, industrial cabinets, medical
networks and telecommunications), styles (the head styles offer padding, head
flat, binding and flat head of 100 degrees
ANSI B18.1.2 is used for rivets of 1/2 inch (1 cm) in diameter and
larger.
This standard covers general and dimensional data for those types of rivets.
large solids recognized as American National Standards along with data
applicable dimensions for heads manufactured after being nailed, heads
rivets and rivets (rolling bar) and impressions of rivet sets.
1.-NPT Threads (National Pipe Thread)
It is a tapered thread very commonly used in the industry. Its origin is American and it is the
acronym for 'National Pipe Thread'.
The nominal diameter (which is merely conventional) originally expressed the
measure of the inner diameter of the tube in inches. It has a finer pitch than the
metric threads and Pg threads.
American National Tapered Pipe Thread, NPT the most known connection and
widely used where the pipe thread provides both mechanical joint and
hydraulic seal.
It has a conical design, the fillets form an angle of 60º and the ridges and valleys are
truncated at 1, 8º.
The diameter is expressed in inches and the pitch in threads per inch.
It is mounted on the same conical thread and the sealing is ensured by a
pre-coating on the thread; requires the use of a sealing product, such as tape
of PTFE, for example.
The taper for all NPT threads is 16 (3/4 inch per foot) measured by the
change in diameter (of the pipe thread) along the distance.
The most commonly used sizes are 1/8, 1/4, 3/8, 3/4, 1 1/4, 1 1/2
It is designated according to ANSI B1.20.1 with the letters NPT preceded by the
nominal diameter in inches and the number of threads per inch separated by a hyphen.
For example: 1/16” – 27 NPT. In the case of having a left-hand thread, the
letters LH.
Example: 3/8 - 18 NPT
Indicates NPT thread type, for 3/8 pipe and 18 threads per inch.
NTP threads with the most common diameters
Diameter (in Diameter Diameter Threads by
inches) exterior interior (mm) inch
1/8 10.28 8,769 27
1/4 13,716 11,145 18
3/8 17,145 14,887 18
1/2 21,336 18,434 14
3/4 26.67 23,768 11 and a half
1 33,401 29,867 11 1/2
1 1/4 42,164 36.67 1 1/2
1 1/2 48.26 44,726 1 and a half
2 60,325 56,791 11 and a half
2 1/2 79,025 67,945 8
The Unified Thread Standard (UTS)
Define a shape and a standard thread series, along with the assignments, the
tolerances and designations for screw threads that are commonly used in
the United States and Canada. It is the main standard for bolts, nuts and a wide
variety of other threaded fasteners used in these countries.
Basic profile
Each thread in the series is characterized by its major diameter and its pitch.
UTS threads consist of a symmetrical V-shaped thread.
In the plane of the thread axis, the flanks of the V have an angle of 60° between them.
The outer 1/8 and the inner 1/4 of the height of the V shape are cut from the
profile.
It has a pitch, the distance between the peaks of the threads.
In this type of threads, the advancement is equal to the axial distance that the screw travels.
during its 360° rotation.
In external threads, the major diameter and the minor diameter define the
maximum dimensions of the thread, that is, the external thread could be rounded.
below the minor diameter, while in an internal thread the diameters
greater and lesser determine the minimum dimensions and therefore the profile of the
The ring may be smaller than the dimensions.
Designation
The standard designation for a UTS thread is a number that indicates the nominal diameter.
(major) of the thread, followed by the pitch measured in threads per inch. For diameters
less than 1/4 inch, the diameter is indicated by a defined integer in the
Standard; for all other diameters, the figure is provided in inches.
Example: # 6-32 UNC 2B
0.1380 inches
step: 32 TPI
Calibration
A screw thread gauge system comprises a list of thread characteristics.
the screws that must be inspected to establish dimensional acceptability of the
screw threads in a threaded product and the gauge or gauges that will be used
inspect those characteristics.
Calibers and ASME / ANSI B1.2-1983 calibers for unified screw threads in
inches
This standard provides essential specifications and dimensions for the gauges
used in unified inch threads UN and UNR in thread form, and covers
the specifications and dimensions of thread gauges and measuring equipment.
ASME / ANSI B1.3-2007 Screw Thread Measurement Systems for
Metric and inch screw threads.
Understand the list of characteristics of screw threads that must be inspected
to establish the dimensional acceptability of screw threads in products
coiled
Both standards provide essential dimensional specifications for gauges
used in unified screw threads in inches in externally threaded products
internally. In addition, it covers the specifications and dimensions of thread gauges and
measurement equipment and also establish the criteria for the acceptance of the threads.
Unified rings come in three different classes:
a) For applications where a liberal tolerance is required to allow a
simple assembly even with slightly chipped threads
b) The most commonly used class for general applications
c) For applications where the accuracy of the fit and/or the accuracy of the elements
the rings are important
Unified screw threads UNC, UNF and UNEF
UNF and UNC are the two main categories of Unified Thread Standard
thread used in the United States. For a given nominal diameter of a screw
exterior, there are fine and thick thread densities (laid from the thread of the screw), measured in threads per
inch. It is used in threads in inches.
UNC Paso Grueso refers to the series of unified thread standards.
normal.
o Side angle of 60°.
Its dimensions are in the imperial system.
It is generally used for the mass production of screws, bolts, and nuts, and
other industrial applications, especially threading in low materials
tensile strength, such as castings, mild steel, and materials
soft, to achieve maximum tear resistance of the thread.
UNF Fine Thread refers to the series of Unified Fine Thread standards.
o Like UNC threads, it has the same design and the same angle of
60° flank.
It has general use, although it is more resistant to tension and torsion than the UNC.
it even withstands loosening due to vibration.
The major diameters are designated in fractions, starting at 1/4"-28UNF
up to 1.1/2”-12UNF.
UNF, Extra Fine Thread Pitch Finodiámetro with Extra Fine Pitch
It is designed with a thread angle of 60° and various combinations.
diameter-pitch.
Compared to the coarse and fine donuts, these have very few steps.
small.
The smallest diameter UNEF is No. 12-32 UNEF and the largest diameter is
1.11/16"-18UNEF.
They are particularly useful in aeronautical equipment due to the high
vibrations involved, and for threads in thin-walled parts.
Designation of unified threads.
It is designated according to the ANSI B1.1 standard with the letters UNC or UNF, which is preceded by the
nominal diameter in inches followed by the threads per inch, for example:
¼” 20 UNC
The designation of unified threads is carried out through the number of threads.
existing in one inch. It also incorporates the thread class, 2A (class 'standard' with
tolerance – a fundamental deviation from nominal diameter – and a tolerance field).
2B being the 'standard' class without tolerance, but only with a tolerance field.
Each series assigns a step to the diameter. For example,
3/8 UNC has 16 threads per inch --- 3/8 - 16
3/8 UNF has 24 threads per inch --- 3/8 - 24
For example, a normal nomenclature in a workshop plan could be:
1/4 – 28 UNF – 3B – LH
This means:
1/4 inch is the nominal major diameter of the thread.
28: it is the number of threads per inch.
UNF: it is the series of threads, in this case unified fine.
3B: the 3 indicates the adjustment (relationship between an internal thread and an external one when it is
B indicates an internal nut. An A indicates an external nut.
LH: indicates that the thread is left-handed. (When no indication is present...)
assume that the thread is right-handed).
Thread in numbered inches UNC and UNF
Designation Diameter Number of Threads Step
nominal
4-40 UNC 2,844 40 0.635