What is a fastener?

What is a fastener?

Fastener is a kind of mechanical parts used for fastening connection and widely used. Fasteners are widely used in various industries, including energy, electronics, electrical appliances, machinery, chemical industry, metallurgy, dies, hydraulic and other industries. A variety of fasteners can be seen in machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, chemical industry, instrumentation and supplies. They are the most widely used mechanical basic parts. Its characteristics are various varieties and specifications, different performance and uses, and the degree of standardization, serialization and generalization is also very high. Therefore, some people refer to a kind of fasteners in the existing national standards as standard fasteners, or abbreviated as standard fasteners.

Material for fasteners Cadmium Plating
Standards for fasteners Application of Fasteners
Types of commonly used thread fasteners Marking of screw or bolt
Nut Marking Marking of gaskets
Marking of retaining ring Screw Thread Tables
Screw Points Flat Washer Thickness Table
Fastener Sizes Fasteners’ Inches to Metric Conversion Chart

The most commonly used material for fasteners:

  • Carbon steel
  • Alloy Steel
  • Stainless Steel: This is the most commonly used material for fasteners.
  • Inconel Stainless steel
  • Titanium: This is mostly used in aircraft application fasteners.
  • Aluminium: This is used in areas of very light loads and application requiring reduction in weight.

Note: Steel low-carbon is generally the default steel selection when no other steel grade is specified, or when no higher grade steel is required. Please check your application needs if you are not certain.

Mechanical Guidelines for Fasteners – Screws, Nuts, Bolts, Washers, Pins

Steel Grade
Material & Treatment
Proof Load Stress
Yield Strength
Tensile Strength
Core Hardness, Rockwell
Standards Authority
ksi (1000 lbs/sq inch) Min.
ksi (1000 lbs/sq inch) Min.
ksi (1000 lbs/sq inch) Min.
Low-carbon grade 2
Low/medium carbon steel, cold-forged
55
57
74
B70-B100
Society of Automotive Engineers
Grade A
Low/medium carbon steel
90-100
95-105
60
B69-B100
American Society for Testing & Materials
Grade B
Low/medium carbon steel
70-133
76-139
60-100
B69-B95
American Society for Testing & Materials
Grade 5
Medium carbon steel, quenched & tempered
74-85
81-82
105-120
C19-C34
Society of Automotive Engineers
Grade 8
Medium carbon alloy steel, quenched & tempered
120
130
150
C33-C39
Society of Automotive Engineers
Grade C
Medium carbon steel
144
154
N/A
B78-C38
American Society for Testing & Materials
2-H
Medium carbon steel
144
154
N/A
B78-C38
Society of Automotive Engineers
Strength guidelines may vary by part thickness, number of threads/inch, finish, and other design or production factors.

Apart from using the above materials as fasteners, certain types of coatings are also provided on the fasteners in order to improve their performance characteristics. The main purpose of coating is to improve the corrosion resistance characteristics of the fasteners. The various types of coatings available for the fasteners are

Cadmium Plating: used mainly for aerospace applications

  • Zinc Plating
  • Phosphate Plating
  • Chromium plating
  • Silver Plating
  • Black Oxidizing
  • Nickel plating

Fastener Plating (Finishes) Chart

Zinc
Cadmium
Zinc Dichromate
zinc - What is a fastener?
cadmium - What is a fastener?
zincdichro - What is a fastener?
Cadmium Dichromate
Galvanized
Black Zinc
cad dichro - What is a fastener?
galvanized - What is a fastener?
blackzinc - What is a fastener?
Phosphate, Black Phosphate
Chrome
Nickel
blackphos - What is a fastener?
chrome - What is a fastener?
MS  38005639P 25 - What is a fastener?

Plating availability based on accessible inventory.

Description
Plating
Corrosion Resistance Level; other Purposes
Zinc Zinc, electroplated Very good
Cadmium Cadmium, electroplated Very good, especially for wet environments
Zinc Dichromate Zinc Dichromate Very good to excellent
Cadmium Dichromate Cadmium Dichromate Very good to excellent
Galvanized Hot-dip Galvanized (electrochemical process) Very good
Black Zinc Zinc, electroplated Very good
Phosphate, Black Phosphate Manganese Phosphate Good
Chrome Chromium, electroplated Good. Useful against physical wear & erosion. Appearance more durable than zinc’s.
Nickel Bright nickel, electroplated Good
Hot Dipped Wax Hot Dip Wax Facilitates easier driving of part; reduces galling
Phosphate & Oil Grey coating with oil bath Moderate; useful against physical wear

Standards for fasteners

  • DIN
  • GB
  • ASME/IFI/ANSI
  • Q
  • EN
  • ISO
  • JIS
  • HG
  • NFE
  • UNI
  • BS
  • Other commonly used standards

Application of Fasteners

Fasteners are a kind of mechanical parts which are widely used for fastening connections. A variety of fasteners can be seen on various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments and supplies. It is characterized by a wide variety of specifications, different performance and uses, and a high degree of standardization, serialization and generalization. Therefore, some people call a class of fasteners in the existing national standards as standard fasteners, or abbreviated as standard fasteners. Fasteners are the most widely used mechanical foundations. With China’s accession to the WTO in 2001, China has entered the ranks of major international trade countries. Fastener products of our country are exported to many countries in the world, and the fastener products of all countries in the world are also pouring into the Chinese market. Fasteners, as one of the products with large import and export volume in China, are of great practical and strategic significance to promote Chinese firms to enter the world and to promote their full participation in international cooperation and competition. Due to the specifications, dimensions, tolerances, weights, properties, surface conditions, marking methods of each specific fastener product, as well as the specific requirements of acceptance inspection, marking and packaging projects.

Common Testing Instruments

The most important link in the development and design of fasteners is quality control. There are several major ports from feeding to finished product delivery. These ports have different inspection methods. First of all, feeding is related to appearance, size, elements, performance, harmful substance detection and so on; process is more about appearance, size, knock test, forging streamline; heat treatment is more about appearance, hardness, torque, tension, metallography, etc; surface treatment is more about hydrogen embrittlement test, coating, salt spray, etc., including the shipment of a harmful substance detection. In size and appearance testing, the common ones are quadratic element, profile measuring instrument, coordinate measuring instrument and image sorting machine (this is a complete sorting machine); in mechanics and chemistry testing, there are mainly hardness machine (Lowe and Vickers), tension machine and metallographic microscope; in material testing, there is a spectrum analyzer and salt spray testing machine.

Types of commonly used thread fasteners

(1) Bolts
20190330104010 17356 - What is a fastener?

The bolt consists of a bolt head and a bolt rod. Hexagonal head shape is the most widely used, and the commonly used grade is A and B. At the same time, it can be divided into full thread, part thread and thick and thin rod. The dimension of bolt specification is determined as nominal diameter D and bolt length L. After selecting one bolt, other parts of the size can be found according to relevant national standards (see attached table).
(2) Double-headed studs
Two ends of the stud are threaded, one end is screwed into the prefabricated screw hole of the connecting part, which is called the screwing end; the other end is screwed with the nut to fasten the other connecting part, which is called the fastening end. In structure, it can be divided into A-level and B-level. Class A should be marked with “A” before specifications and Class B should not be marked. The length of the screw-in end of the double-headed stud is related to the material of the connecting parts with screw holes:

  • Bronze and steel, BM = D
  • Cast iron, BM = 1.25d
  • Aluminum alloy, BM = 1.5D
  • Non-metallic materials, BM = 2D

The dimension of the twin-head stud is determined to be the diameter D of the stud and the length L of the fastening end. After choosing a twin-head stud, the dimensions of other parts can be found according to the relevant standards.
(3) Screws
20190330104033 25403 - What is a fastener?

The screw can be divided into connecting screw and fastening screw according to the nature of use. The former is used for connection, according to the shape of the head, there are slotted cylindrical head screw, slotted countersunk head screw, slotted disc head screw and so on. The latter is mainly used to prevent relative movement between two matching parts, such as slotted flat-end fastening screw, slotted taper-end fastening screw, inner hexagonal flat-end fastening screw, etc. The size of the screw is determined to be the diameter D and length L of the screw. The dimensions of other parts can be found according to the relevant standards.
(4) Nuts
Nuts are used in conjunction with bolts or studs to connect. Nuts in the form of hexagonal, round, square, etc., hexagonal head nut is the most common application. Round nuts are often used for axially fixing parts on axes. Hexagonal head nuts can be divided into type I, II, A, B and C, as well as thickness and thickness. The nominal diameter D of the thread determines the size of the nut specifications. After selecting a nut, the other parts of the size can be found according to the relevant standards.
(5) Gaskets
The washer is installed between the nut and the connector. Its purpose is to increase the contact area between the nut and the connector, and to protect the surface of the connector from scratching when tightening the nut. In addition to flat washers, there are spring washers and stop washers, which can prevent nuts from loosening due to vibration.
The dimension of the gasket is determined to be bolt diameter D. After selecting the gasket, the dimensions of other parts can be found according to the relevant standards.

(6) Nails

One of the easiest fasteners used to affix pieces of wood intact.

20190330104053 55526 - What is a fastener?

(7) Clamps

Clamps are the best fasteners available for fastening objects only for a limited period of time without causing damage to the object while it is unfastened.

20190330104125 68158 - What is a fastener?

(8) Tapping screws

These are fasteners that enable quick installation which create a mating thread when fastened into a performed hole of the object. This process is known as thread forming. The installation is quick tapping screws does not employ buts for fastening.

20190330104150 96255 - What is a fastener?

(9) Set Screws

Set screws are used hold intact pulleys, collars, gears with a shaft. This semi – permanent fasteners are available in various heads and points styles.

20190330104214 75896 - What is a fastener?

(10) Studs

Studs are headless fasteners which are threaded externally. In this, one end of the fastener connects with a tapped part while the other end meets with a standard nut. The forms of bolt and screw heads vary with the usage of the fastener. Some of the different forms in terms of shape include:

20190330104233 21770 - What is a fastener?
  • Bolt Heads – square, eye-shaped, hexagonal etc.,
  • Screw heads – Button head, counter sunk, hexagonal, etc.,

1. Marking of screw or bolt: name, standard number, nominal diameter * pitch * nominal length – material – screw form – surface treatment

  • A) Name: Use the standard names specified in the national standard, such as: screw, bolt, nut, tapping screw, screw assembly, plastic screw, etc.
  • B) Standard number: label the national label, the Ministry label or the enterprise label (not the year number). If our company designs it by itself, label the model of the product it belongs to.
  • C) Pitch: Only for fine threads, rough teeth are omitted.
  • D) Material: If carbon steel is used, this part is omitted, otherwise it should be noted, such as copper, C1 (stainless steel). Stainless steel material code see GB3098.6, which: austenite, A1, A2, A4; martensite, C1, C3, C4; ferrite, F1.)
  • E) Twisting form: If the standard form of Twisting is adopted, it will be omitted, otherwise it should be injected, such as composite slot.
  • F) Surface treatment: If it is galvanizing passivation of carbon steel, it is omitted. Otherwise, it should be noted, such as copper/Ni (copper-nickel plating), copper/Ni6b (copper-bright nickel plating, nickel layer thickness of 6 microns), copper/Sn (copper-tin plating), copper/Sn (60) Pb (copper-lead-tin plating), Fe/Ni6bCr0.3r (carbon-steel-nickel-chromium plating), O (surface oxidation), stainless steel materials usually do not need to be coated. If the coating complies with ROHS instructions, it is marked after surface treatment and placed in brackets.

Note 1: If the material and surface treatment are not indicated in the label of the fastener, it means that the material of the fastener is galvanized passivation of carbon steel (i.e. galvanized).
Note 2: There are two types of tapping screw, C type and F type, C type is pointed face, F type is flat face. But the self-tapping locking screw is not classified.
Note 3: The difference between the disc head and the cylinder head is that the diameter of the disc head is slightly larger than that of the cylinder head, but the thickness of the head is slightly thinner than that of the cylinder head.
Note 4: The difference between a countersunk head and a semi-countersunk head is that the head of a countersunk head is flat, while the head of a semi-countersunk head is curved, and the thickness of the head of a countersunk head is thinner than that of a semi-countersunk head.
Note 5: The difference between the fastening screw and the ordinary screw is that the head shape of the ordinary screw is T-shaped, while the fastening screw has no T-shaped head.
Note 6: Slotting means that the head is a slot. Compound groove, cross groove and word groove can be used in general, but the same batch of products should be unified.
Note 7: For stainless steel fasteners, since our employees are not familiar with their code, we can put “stainless steel” in brackets after the material code.
Note 8: Difference between Screws and Bolts
Screw: It is composed of head and screw. It is used where there are prefabricated threads. It does not need to be matched with nuts. Internal wrench is commonly used, and there are often holes in the head.
Bolt: It is composed of head and screw. It should be matched with nut to fasten the parts with two through holes. External wrench, often hexagonal head.
Note 9: If the screw assembly meeting the XXXX enterprise standard is selected, the marks are: screw assembly ZBY1 (combination of screw and round cushion), ZBYA1 (combination of screw and round cushion, round cushion), ZBF1 (combination of screw and square cushion), ZBFA1 (combination of screw and square cushion, square cushion).
2. Nut Marking: Name, Standard Number, Nominal Diameter *Pitch-Material-Surface Treatment

  • A) Name: Use the standard name specified in the national standard, such as nuts.
  • B) The labeling method of standard number, pitch, material and surface treatment is the same as that of screw.

3. Marking of gaskets: name, standard number, nominal diameter * pitch – material – surface treatment

  • A) Name: The national standard stipulates that the standard names of flat washers and spring washers are “washers”, but in view of our company’s actual situation, in order to avoid confusion, flat washers are universally named “flat cushions” and spring washers are universally named “bullet cushions”.
  • B) Nominal specification: refers to the big diameter of thread, such as the big diameter of external thread M 8 is 8.
  • C) The labeling method of standard number, material and surface treatment is the same as that of screw.
  • D) If the material and surface treatment are not indicated in the marking of the cushion, it means that the material is 65Mn and the surface treatment is surface oxidation.

4. Marking of retaining ring: name, standard number, nominal specification

  • A) Name: Uniform name for “retaining ring”. Nominal specification: refers to shaft diameter or aperture. The labeling method of the standard number is the same as that of the screw.
  • B) The material of the retaining ring is 65Mn, and the surface treatment is surface oxidation.
  • Note 10: In addition, the cylindrical pin is the fastener commonly used by our company in the manufacture of dies. Its standard number is GB/T119-86. Marking example: pin GB/T119 A 6*40 (denoting nominal diameter – large end diameter is_6, nominal length is 40, material is carbon steel, surface oxidation treatment, A shape).

Note 11: When choosing fasteners, we should first choose from the existing order number of BOM list, and try to choose fasteners commonly used or in large stock. New selections are allowed only when all the components in the existing BOM database are confirmed to be inappropriate.
Note 12: In BOM system, all’*’numbers in fastener labels are denoted by’*’.

Note 13: When the fastener marking format specified in these Rules can not express all its elements, it is allowed to add suffixes at the end of this naming format and place them in brackets, such as (XX exclusive), (natural color), etc.

Screw Thread Tables
Coarse Thread Table

Nominal Size
Major Diameter
Threads/inch
Basic Pitch Diameter
Minor Diameter
Lead Angle
at Basic Pitch Diameter
Height of Fundamental Triangle
Tensile Stress Area
(Degrees)
(Min)
(square inches)
#1 0.073 64 0.063 0.056 4 31 0.01353
0.003
#2 0.086 56 0.074 0.067 4 22 0.01547
0.004
#3 0.099 48 0.086 0.076 4 26 0.01804
0.005
#4 0.112 40 0.096 0.085 4 45 0.02165
0.006
#5 0.125 40 0.109 0.098 4 11 0.02165
0.008
#6 0.138 32 0.118 0.104 4 50 0.02706
0.009
#8 0.164 32 0.144 0.130 3 58 0.02706
0.014
#10 0.190 24 0.163 0.145 4 39 0.03608
0.018
#12 0.216 24 0.189 0.171 4 1 0.03608
0.024
1/4 0.250 20 0.218 0.196 4 11 0.04330
0.032
5/16 0.313 18 0.276 0.252 3 40 0.04811
0.052
3/8 0.375 16 0.334 0.307 3 24 0.05413
0.078
7/16 0.438 14 0.391 0.360 3 20 0.06186
0.106
1/2 0.500 13 0.450 0.417 3 7 0.06662
0.142
9/16 0.563 12 0.508 0.472 2 59 0.07217
0.182
5/8 0.625 11 0.566 0.527 2 56 0.07873
0.226
3/4 0.750 10 0.685 0.642 2 40 0.08660
0.334
7/8 0.875 9 0.803 0.755 2 31 0.09623
0.462
1 1.000 8 0.919 0.865 2 29 0.10825
0.606
1 1/8 1.125 7 1.032 0.941 2 31 0.12372
0.763
1 1/4 1.250 7 1.157 1.095 2 15 0.12372
0.969
1 3/8 1.375 6 1.267 1.195 2 24 0.14434
1.155
1 1/2 1.500 6 1.392 1.320 2 11 0.14434
1.405
1 3/4 1.750 5 1.620 1.534 2 15 0.17321
1.900
2 2.000 4 1/2 1.856 1.759 2 11 0.19245
2.500
2 1/4 2.250 4 1/2 2.106 2.009 1 55 0.19245
3.250
2 1/2 2.500 4 2.338 2.229 1 57 0.21651
4.000
2 3/4 2.750 4 2.588 2.479 1 46 0.21651
4.930
3 3.000 4 2.838 2.729 1 36 0.21651
5.970
3 1/4 3.250 4 3.088 2.979 1 29 0.21651
7.100
3 1/2 3.500 4 3.338 3.229 1 22 0.21651
8.330
3 3/4 3.750 4 3.588 3.479 1 16 0.21651
9.660
4 4.000 4 3.838 3.729 1 11 0.21651
11.080
TRANS - What is a fastener?
(standards set by American Society of Mechanical Engineers)

Fine Thread Table

Basic Dimensions for Fine Thread Series Parts (UNF/UNRF)
(measured in inches)
Nominal Size
Major Diameter
Threads/inch
Basic Pitch Diameter
Minor Diameter
Lead Angle
at Basic Pitch Diameter
Height of Fundamental Triangle
Tensile Stress Area
(Degrees)
(Min)
(square inches)
#0
0.060 80 0.052 0.047 4 23
0.01083
0.002
#1
0.073 72 0.064 0.058 3 57
0.01203
0.003
#2
0.086 64 0.076 0.069 3 45
0.01353
0.004
#3
0.099 56 0.087 0.080 3 43
0.01547
0.005
#4
0.112 48 0.099 0.089 3 51
0.01804
0.007
#5
0.125 44 0.110 0.100 3 45
0.01968
0.008
#6
0.138 40 0.122 0.111 3 44
0.02165
0.010
#8
0.164 36 0.146 0.134 3 28
0.02406
0.015
#10
0.190 32 0.170 0.156 3 21
0.02706
0.020
#12
0.216 28 0.193 0.177 3 22
0.03093
0.026
1/4
0.250 28 0.227 0.211 2 52
0.03093
0.036
5/16
0.313 24 0.285 0.267 2 40
0.03608
0.058
3/8
0.375 24 0.348 0.330 2 11
0.03608
0.088
7/16
0.438 20 0.405 0.383 2 15
0.04330
0.119
1/2
0.500 20 0.468 0.446 1 57
0.04330
0.160
9/16
0.563 18 0.526 0.502 1 55
0.04811
0.203
5/8
0.625 18 0.589 0.565 1 43
0.04811
0.256
3/4
0.750 16 0.709 0.682 1 36
0.05413
0.373
7/8
0.875 14 0.829 0.798 1 34
0.06186
0.509
1
1.000 14 0.946 0.903 1 36
0.07217
0.663
1 1/8
1.125 12 1.071 1.035 1 25
0.07217
0.856
1 1/4
1.250 12 1.196 1.160 1 16
0.07217
1.073
1 3/8
1.375 12 1.321 1.285 1 9
0.07217
1.315
1 1/2
1.500 12 1.446 1.410 1 3
0.07217
1.581
(standards set by American Society of Mechanical Engineers)

Screw Points


Type AFound on Sheet Metal (Tapping) Screws 
TypeA - What is a fastener?
Type A tapping screws have coarse threads and gimlet points. They are used in thin metal, resinous plywood, and various composite boards.

Type AB: Found on Sheet Metal (Tapping) Screws
TypeAB - What is a fastener?
Type AB tapping screws have spaced threads and gimlet points. Like the Type A, they are used in thin metal, resinous plywood, and various composite boards. Type AB screws offer a wider range of applications over Type A screws.

Type B: Found on Sheet Metal (Tapping) Screws
TypeB - What is a fastener?
Type B tapping screws have spaced threads and a blunt point with incomplete entering threads. They are used in thin metal, nonferrous castings, resinous plywood, plastics, and various composite boards.

Type 25: Found on Thread Cutting Screws
Type25 - What is a fastener?
Also known as Type BT, Type 25 screws have spaced, incomplete tapered threads with a blunt point and tapered entering edges, with one or more cutting edges and chip removal indentations. They are used in plastic, asbestos compositions, and other composites.

Type F: Found on Thread Cutting Screws
TypeF - What is a fastener?
Type F screws have machine screw threads with a blunt point and tapered entering edges, with one or more cutting edges and chip removal indentations. They are used in nonferrous castings, steel sheets, plastics, brass, cast iron, etc.

Type 23: Found on Thread Cutting Screws
Type23 - What is a fastener?
Also known as Type T, Type 23 screws have machine screw threads with a blunt point and tapered entering edges, with one or more cutting edges and chip removal indentations. In this sense they are similar to Type F screws. The cutting edge on the point, however, is broader and deeper than that of the Type F. Type 23 screws are also used in nonferrous castings, steel sheets, plastics, brass, cast iron, etc.

Type 17: Found on Thread Cutting Screws
Type17 - What is a fastener?
A thread cutting screw especially for wood, with a coarse tapping screw thread and a special long sharp point fluted to capture chips.

Teks screw (Self-Drilling Screw)
Type2 - What is a fastener? Type3 - What is a fastener?
Type 2
Type 3

Teks screws, also known as self drilling screws, drill their own hole in thin sheet metal, heavier gauge metals and other materials, then form close mating threads in the hole. The Teks screw is ideal for automated assembly and reduces or eliminates the need for drill bits or taps. Once the hole is drilled, Teks screws (self drilling screws) tap the hole in the same way as thread forming or thread cutting screws do in a pre-drilled hole. They are also designed to eliminate paint build-up, weld flash, or foreign material that may occur in pre-drilled or pre-punched holes.

Type U-drive:
TypeU - What is a fastener?

U-Drive screws are round head metallic drive screws having multiple start threads of large helix angle, with a pivot. Featuring case-hardened threads, designed to be harder than the mating part. The Type U-Drive Screw is used when an attachment is not meant to be removed. It is driven into an undersized hole for great adherence, usually in metals or plastics. U-Drive Screws also have a round, unslotted head, again intended for a permanent fixture.

Flat Washer Thickness Table

Steel Gage Thicknesses

The Flat Washer Gage Thickness/Plain Washer Gage Thickness Table displays standardized steel thicknesses for standard flat washers (also known as plain washers). Washers are manufactured from Strip & Tube steels. Gage Numbers are standardized strip/tube steel thicknesses. These gage thicknesses are standards among manufacturers of strip & tube steel. Gage measurements are in inches.

 
Thickness
Gage Number
 
Gage Measurement (in inches)
00000
 
0.500
0000
 
0.454
000
 
0.425
00
 
0.380
0
 
0.340
1
 
0.300
2
 
0.284
3
 
0.259
4
 
0.238
5
 
0.220
6
 
0.203
7
 
0.180
8
 
0.165
9
 
0.148
10
 
0.134
11
 
0.120
12
 
0.109
13
 
0.095
14
 
0.083
15
 
0.072
16
 
0.065
17
 
0.058
18
 
0.049
19
 
0.042
20
 
0.035
21
 
0.032
22
 
0.028
23
 
0.025
24
 
0.022
25
 
0.020
26
 
0.018
27
 
0.016
28
 
0.014
29
 
0.013
30
 
0.012
31
 
0.010
32
 
0.009
33
 
0.008
34
 
0.007
35
 
0.005
36
 
0.004

Fastener Sizes

The Size Dimension pertains to diameter of screws, bolts, & pins and inner diameter of nuts and washers. You may search for your product based on diameter by selecting a measurement on the Size dropdown. Other size measurements, such as screw, bolts, pin length, the outer diameters of nuts & washers, etc., appear on the search result itself.

A. Parts that Require Matching with a Mating Item

For example: Screws or bolts that drill through nuts, washers
Those parts that require matching with a mating item – screws or bolts with nuts or washers – have diameters that are denominated in actual inches or fractions thereof, followed by the number of threads per inch.
Screws and bolts that mate with a nut, as well as the nuts themselves, are denominated as such. Washers are not.
Examples:

1. A fraction followed by a hyphen, followed by a number:

The fraction is the diameter of the shaft, in fraction of an inch. The number following the hyphen is the number of threads per inch, that is, the number of threads on the shaft itself, per inch of shaft length.

  • 1/4-20: One quarter inch shaft diameter, 20 threads per inch
  • 3/4-16: Three quarter inch shaft diameter, 16 threads per inch

2. For parts 1 inch or larger:

A number 1 or number larger than one, or number one or number larger than one followed by a fraction, then followed by a hyphen then a fraction or whole number:
The number 1 or number larger than one, or number one or number larger than one followed by a fraction, is the diameter of the shaft. The number following the hyphen is the number of threads per inch; that is, the number of threads on the shaft itself, per inch of shaft length. Same as for smaller parts.

  • 1-12: One inch shaft diameter, 12 threads per inch
  • 2-1/4-4-1/2: Two and one quarter inch shaft diameter, four and a half threads per inch

Note: The diameters of some smaller machine screws (though they may take a mating part), are denominated with the industry Numeric Size system described below. See section C below for clarification.

B. Parts that do not Require Matching with a Mating Item

Those parts that do not require matching with a mating item – screws or bolts that simply drill into or through a surface – are often denominated by industry Numeric Sizes preceded by a # sign. These do not show a number of threads-per-inch designation. These industry Numeric Sizes run from #0 through #15, with #0 the smallest and #15 the largest.
These Numeric Sizes are shaft diameters (and inner diameters of some washers) that were standardized years ago by the American Society of Mechanical Engineers (ASME), American Society of Testing & Materials (ASTM), and other standards bodies. These sizes were standardized based on sizes already commonly in use in the market.

1. Examples:

An industry Numeric Size, preceded by a # sign:

  • #6: A Number 6 size (sheet metal screws, Teks screws, drywall screws, particle board screws, wood screws, U-drive screws)
  • #8: A Number 8 size (sheet metal screws, Teks screws, drywall screws, particle board screws, wood screws, U-drive screws)
  • #14: A Number 14 size (sheet metal screws, Teks screws, wood screws)

2. Basic Major Diameters of industry Numeric Size-denominated screws:

(in inches)

  • #0: 0.0600 or 3/50 in 
  • #1: 0.0730 or 73/1000 in 
  • #2: 0.0860 or 43/500 in 
  • #3: 0.0990 or 99/1000 in 
  • #4: 0.1120 or 14/125 in 
  • #5: 0.1250 or 1/8 in 
  • #6: 0.1380 or 69/500 in
  • #7: 0.151 or 77/512
  • #8: 0.1640 or 41/250 in 
  • #10: 0.1900 or 19/100 in 
  • #12: 0.2160 or 27/125 in 
  • #14: 0.2500 or ¼ in 
  • #15: 0.3750 or 3/8 in

Numeric Size denominations larger than #15 are uncommon.
Diameters are based on ASME Coarse Thread Series (UNC/UNRC) and ASME Fine Thread Series (UNF/UNRF)
C. Machine Screw Diameters denominated with the industry Numeric Size system
The diameters of smaller machine screws are denominated with the same Basic Major Diameters of industry Numeric Size-denominated screws noted in section B. 2. above, but with a number of threads per inch count as well. Here follows a list, in inches:

  • 2-56: 0.0860 or 43/500 in diameter; 56 threads per inch
  • 4-40: 0.1120 or 14/125 in diameter; 40 threads per inch
  • 5-40: 0.1250 or 1/8 in diameter; 40 threads per inch
  • 6-32: 0.1380 or 69/500 in diameter; 32 threads per inch
  • 8-32: 0.1640 or 41/250 in diameter; 32 threads per inch
  • 10-32: 0.1900 or 19/100 in diameter; 32 threads per inch
  • 10-24: 0.1900 or 19/100 in diameter; 24 threads per inch
  • 12-24: 0.2160 or 27/125 in diameter; 24 threads per inch

Fasteners’ Inches to Metric Conversion Chart

 

Inches
Inches
Millimeters
Centimeters
Meters
Fractional
Decimal
1/64
0.0156
0.3969
0.03969
0.000397
1/32
0.0312
0.7925
0.07925
0.000793
3/64
0.0469
1.1906
0.11906
0.001191
1/16
1/16
0.0625
1.5875
0.15875
0.001588
5/64
0.0781
1.9844
0.19844
0.001984
3/32
0.0938
2.3813
0.23813
0.002381
7/64
0.1094
2.7781
0.27781
0.002778
1/8
1/8
0.1250
3.1750
0.3175
0.003175
9/64
0.1406
3.5719
0.35719
0.003572
5/32
0.1562
3.9675
0.39675
0.003968
11/64
0.1719
4.3656
0.43656
0.004366
3/16
3/16
0.1875
4.7625
0.47625
0.004763
13/64
0.2031
5.1594
0.51594
0.005159
7/32
0.2188
5.5563
0.55563
0.005556
15/64
0.2344
5.9531
0.59531
0.005953
1/4
1/4
0.2500
6.3500
0.635
0.00635
17/64
0.2656
6.7469
0.67469
0.006747
9/32
0.2812
7.1425
0.71425
0.007143
19/64
0.2969
7.5406
0.75406
0.007541
5/16
5/16
0.3125
7.9375
0.79375
0.007938
21/64
0.3281
8.3344
0.83344
0.008334
11/32
0.3438
8.7313
0.87313
0.008731
23/64
0.3594
9.1281
0.91281
0.009128
3/8
3/8
0.3750
9.5250
0.9525
0.009525
25/64
0.3906
9.9219
0.99219
0.009922
13/32
0.4062
10.3175
1.03175
0.010318
27/64
0.4219
10.7156
1.07156
0.010716
7/16
7/16
0.4375
11.1125
1.11125
0.011113
29/64
0.4531
11.5094
1.15094
0.011509
15/32
0.4688
11.9063
1.19063
0.011906
31/64
0.4844
12.3031
1.23031
0.012303
1/2
1/2
0.5000
12.7000
1.27
0.0127
33/64
0.5156
13.0969
1.30969
0.013097
17/32
0.5312
13.4925
1.34925
0.013493
35/64
0.5469
13.8906
1.38906
0.013891
9/16
9/16
0.5625
14.2875
1.42875
0.014288
37/64
0.5781
14.6844
1.46844
0.014684
19/32
0.5938
15.0813
1.50813
0.015081
39/64
0.6094
15.4781
1.54781
0.015478
5/8
5/8
0.6250
15.8750
1.5875
0.015875
41/64
0.6406
16.2719
1.62719
0.016272
21/32
0.6562
16.6675
1.66675
0.016668
43/64
0.6719
17.0656
1.70656
0.017066
11/16
11/16
0.6875
17.4625
1.74625
0.017463
45/64
0.7031
17.8594
1.78594
0.017859
23/32
0.7188
18.2563
1.82563
0.018256
47/64
0.7344
18.6531
1.86531
0.018653
3/4
3/4
0.7500
19.0500
1.905
0.01905
49/64
0.7656
19.4469
1.94469
0.019447
25/32
0.7812
19.8425
1.98425
0.019843
51/64
0.7969
20.2406
2.02406
0.020241
13/16
13/16
0.8125
20.6375
2.06375
0.020638
53/64
0.8281
21.0344
2.10344
0.021034
27/32
0.8438
21.4313
2.14313
0.021431
55/64
0.8594
21.8281
2.18281
0.021828
7/8
7/8
0.8750
22.2250
2.2225
0.022225
57/64
0.8906
22.6219
2.26219
0.022622
29/32
0.9062
23.0175
2.30175
0.023018
59/64
0.9219
23.4156
2.34156
0.023416
15/16
15/16
0.9375
23.8125
2.38125
0.023813
61/64
0.9531
24.2094
2.42094
0.024209
31/32
0.9688
24.6063
2.46063
0.024606
63/64
0.9844
25.0031
2.50031
0.025003
1 inch
1
1.0000
25.4000
2.54
0.0254
6 inches
6
6.0000
152.4000
15.24
0.1524
12 inches
12
12.0000
304.8000
30.48
0.3048
24 inches
24
24.0000
609.6000
60.96
0.6096
36 inches
36
36.0000
914.4000
91.44
0.9144

Source: China Fasteners Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

References:

  • https://www.instockfasteners.com
Summary
what is a fastener - What is a fastener?
Article Name
What is a fastener?
Description
Fastener is a kind of mechanical parts used for fastening connection and widely used. Fasteners are widely used in various industries, including energy, electronics, electrical appliances, machinery, chemical industry, metallurgy, dies, hydraulic and other industries.
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www.steeljrv.com
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