ASME B18.3 Hexagon Socket Set Screws

ASME B18.3 Hexagon Socket Set Screws

ASME B18.3 Dimensions of Hexagon Socket Set Screws

Nominal Size (Basic Screw Diameter) Nominal Hexagon Socket Size, J Minimum Key Engagement to Develop Functional Capability of Key, T Cup and Flat Point Diameters, C Basic Oval Point Radius, R Cone Point Angle 90 deg ± 2 deg for These Nominal Lenghts or Longer: 118 deg ± 2 deg for Shorter Nominal Lenghts, Y Half Dog Point Shortest Optimum Nominal Length to Which THApplies, B Shortest Optimum Nominal Length to Which Ts Applies,
B1
Diameter, P Length, Q Cup and Flat Points 90 deg Cone and Oval Points Half Dog Points Cup and Flat Points 90 deg Cone and Oval Points Half Dog Points
Hex Socket, TH Max. Min. Max. Min. Max. Min.
0 (0.0600) ... 0.028 0.050 0.033 0.027 0.045 0.09 0.040 0.037 0.017 0.13 0.13 0.13 0.13 0.06 0.13 0.13
1 (0.0730) ... 0.035 0.060 0.040 0.033 0.055 0.09 0.049 0.045 0.021 0.017 0.13 0.19 0.13 0.13 0.19 0.13
2 (0.0860) ... 0.035 0.060 0.047 0.039 0.064 0.13 0.057 0.053 0.024 0.020 0.13 0.19 0.19 0.13 0.19 0.19
3 (0.0990) ... 0.050 0.070 0.054 0.045 0.074 0.13 0.066 0.062 0.027 0.023 0.19 0.19 0.19 0.13 0.19 0.19
4 (0.1120) ... 0.050 0.070 0.061 0.051 0.084 0.19 0.075 0.070 0.030 0.026 0.19 0.19 0.19 0.13 0.19 0.19
5 (0.1250) 1/16 0.062 0.080 0.067 0.057 0.094 0.19 0.083 0.078 0.033 0.027 0.19 0.19 0.19 0.13 0.19 0.19
5 (0.1250) 1/16 0.062 0.080 0.067 0.057 0.094 0.19 0.083 0.078 0.033 0.027 0.19 0.19 0.19 0.13 0.19 0.19
6 (0.1380) 1/16 0.062 0.080 0.074 0.064 0.104 0.19 0.092 0.087 0.038 0.032 0.19 0.25 0.19 0.13 0.25 0.19
6 (0.1380) 1/16 0.062 0.080 0.074 0.064 0.104 0.19 0.092 0.087 0.038 0.032 0.19 0.25 0.19 0.13 0.25 0.19
8 (0.1640) 5/64 0.078 0.090 0.087 0.076 0.123 0.25 0.109 0.103 0.043 0.037 0.19 0.25 0.19 0.13 0.25 0.19
10 (0.1900) 3/32 0.094 0.100 0.102 0.088 0.142 0.25 0.127 0.120 0.049 0.041 0.19 0.25 0.25 0.19 0.25 0.25
1/4 (0.2500) 1/8 0.125 0.125 0.132 0.118 0.188 0.31 0.156 0.149 0.067 0.059 0.25 0.31 0.31 0.25 0.31 0.31
5/16 (0.3125) 5/12 0.156 0.156 0.172 0.156 0.234 0.38 0.203 0.195 0.082 0.074 0.31 0.44 0.38 0.31 0.44 0.38
3/8 (0.3750) 3/16 0.188 0.188 0.212 0.194 0.281 0.44 0.250 0.241 0.099 0.089 0.38 0.44 0.44 0.38 0.44 0.44
7/16 (0.4375) 7/32 0.219 0.219 0.252 0.232 0.328 0.50 0.297 0.287 0.114 0.104 0.44 0.63 0.50 0.44 0.63 0.50
1/2 (0.5000) 1/4 0.250 0.250 0.291 0.270 0.375 0.57 0.344 0.334 0.130 0.120 0.50 0.63 0.63 0.50 0.63 0.63
5/8 (0.6250) 5/16 0.312 0.312 0.371 0.347 0.469 0.75 0.469 0.456 0.164 0.148 0.63 0.88 0.88 0.63 0.88 0.88
3/4 (0.7500) 3/8 0.375 0.375 0.450 0.425 0.562 0.88 0.562 0.549 0.196 0.180 0.75 1.00 1.00 0.75 1.00 1.00
7/8 (0.8750) 1/2 0.500 0.500 0.530 0.502 0.656 1.00 0.656 0.642 0.227 0.211 0.88 1.00 1.00 0.88 1.25 1.00
1 (1.0000) 9/16 0.562 0.562 0.609 0.579 0.750 1.13 0.750 0.734 0.260 0.240 1.00 1.25 1.25 ... ... ...
1 1/8 (1.1250) 9/16 0.562 0.562 0.689 0.655 0.844 1.25 0.844 0.826 0.291 0.271 1.25 1.50 1.25 ... ... ...
1 1/4 (1.2500) 5/8 0.625 0.625 0.767 0.733 0.938 1.50 0.938 0.920 0.323 0.303 1.25 1.50 1.50 ... ... ...
1 3/8 (1.3750) 5/8 0.625 0.625 0.848 0.808 1.031 1.63 1.031 1.011 0.354 0.334 1.50 1.75 1.50 ... ... ...
1 1/2 (1.5000) 3/4 0.750 0.750 0.926 0.886 1.125 1.75 1.125 1.105 0.385 0.365 1.50 2.00 1.75 ... ... ...
1 3/4 (1.7500) 1 1.000 1.000 1.086 1.039 1.312 2.00 1.312 1.289 0.448 0.428 1.75 2.25 2.00 ... ... ...
2 (2.0000) 1 1.000 1.000 1.244 1.193 1.500 2.25 1.500 1.474 0.510 0.490 2.00 2.50 2.50 ... ... ...

GENERAL NOTE: For additional requirements, refer to Notes (5) through (15) and section 2, General Data, of this Standard.
NOTES:

(1) Face. The plane of the face on the socket end of the screw shall be approximately normal to the axis of the screw, and shall be chamfered on screws longer than lengths listed in this Table, columns B and B1. The chamfer angle, V, shall be between 30 deg and 45 deg. The chamfer shall extend slightly below the root diameter of the thread and the edge between flat and chamfer may be slightly rounded. For screws equal to or shorter than the lengths listed in this Table, columns B and B1, or screws 0.250 in. diameter or greater, with a national coarse thread, including lengths longer than listed in this Table, columns B and B1, chamfering shall be at the option of the manufacturer. If chamfered, the chamfer angle, V, shall not exceed 45 deg.

(2) Point Angles. Point angles specified shall apply only to those portions of the angles that lie below the root diameter of the thread. The angles may vary in the threaded portions due to manufacturing processes. W shall be 45 deg, +5 deg −0 deg, for screws of lengths equal to or longer than the lengths listed in this Table, columns B and B1, and 30 deg minimum for shorter screws.

(3) Oval Point Radius Tolerance. The tolerance shall be +0.015 in. for screw nominal sizes through 5 (0.125 in.) and +0.031 in. for screw nominal sizes 6 (0.138 in.) and larger.

(4) Cone Point Configuration. The apex of the cone may be flatted or rounded to the extent of 10% of the basic diameter of the screw.

(5) Nominal Size. Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted.

(6) Length. The length of the screw shall be measured overall, parallel to the axis of the screw. The basic length dimension on the product shall be the nominal length expressed as a two-place decimal.

(7) Standard Lengths. Standard length increments for set screws shall be as tabulated below.

Nominal Screw Length Standard Length Increments
0.13 through 0.19* 0.3
0.19 through 0.50* 0.06
0.50 through 1.00* 0.13
1.00 through 2.00 0.25
2.00 through 6.00 0.50
Over 6.00 1.00

*A nominal screw length of 0.13 through 0.19 is applicable only to nominal sizes 0 (0.060 in.) through 3 (0.099 in.), inclusive.

(8) Hexagon Sockets. See Table 6 for hexagon socket dimensions and Mandatory Appendix I for gaging of hexagon sockets.

(9) Socket Depths. The key engagement dimensions shall apply only to nominal screw lengths equal to or longer than the lengths listed in this Table, columns B and B1, respectively. For hexagon socket key engagement dimensions in screws of shorter nominal lengths than those listed in column B of this Table, see Table 15.

(10) Half Dog Point Runout. The runout of the half dog point shall not exceed 3% of the nominal size and shall not exceed 0.010 FIM for nominal sizes up to and including 3⁄4 in. diameter and 0.020 FIM for nominal sizes over 3⁄4 in. diameter. Runout is defined as the full indicator movement (FIM) obtained by holding on the thread major diameter near the half dog point, and rotating the screw 360 deg and indicating on the half dog point diameter.

Tolerance on Length. Tolerance on length of set screws shall be tablutad below.

Nominal Screw Length Tolerance on Length
Up to 0.63, incl. ±0.01
Over 0.63 to 2.00, incl. ±0.02
Over 2.00 to 6.00, incl, ±0.02
Over 6.00 ±0.06

(12) Threads. Threads shall be Unified external thread: Class 3A, UNC and UNF Series. Thread lead deviation is controlled by standard thread gages within a thread length equal to 1.5 basic thread diameters. When using set screws longer than 1.5 basic diameters in length, the pitch diameter of the set screw may need to be reduced, or the tapped hole’s pitch diameter may need to be increased to avoid interference during assembly. Thread acceptability shall be based on System 22, ASME B1.3. NOT GO gaging shall not be required for set screws equal to or shorter than 7-pitch lengths. Class 3A threads do not provide a plating allowance. When set screws must be plated, they should be manufactured with an undersized pitch diameter to accommodate the plating.

(13) Material
(a) Steel, Alloy. Socket set screws shall be fabricated from alloy steel and shall conform in all respects to ASTM F912.
(b) Steel, Corrosion-Resistant. Socket set screws shall be fabricated from austenitic corrosion-resistant steel and shall conform in all respects to ASTM F880.

(14) Flat Point. The plane of the end on the flat point shall be perpendicular to the axis of the thread within 2 deg obtained by holding the screw on the major thread diameter near the flat point, and inspecting on an optical comparator or comparable inspection equipment.

(15) Designation. To promote uniformity and understanding in communications relating to products conforming to this Standard, it is recommended that Hexagon Socket Set Screws be designated in accordance with the following data, preferably in the sequence shown:
(a) product name and point style
(b) designation of the standard
(c) nominal size (number, fractional or decimal equivalent)
(d) thread pitch
(e) nominal length (fractional or decimal equivalent)
(f) material
(g) protective finish, if required
EXAMPLES:
Hexagon Socket Set Screw, Cup Point, ASME B18.3, 1⁄4-20  1⁄4 , Alloy Steel
Hexagon Socket Set Screw, Cup Point, ASME B18.3, 6-32  0.250, Corrosion-Resistant Steel
For the recommended B18 part identifying numbering system (PIN), see ASME B18.24.