Table 8

SOCKET CAP, SHOULDER, AND SET SCREWS, HEX AND SPLINE KEYS (INCH SERIES) ASME B18.3-1998

TABLE 8 DIMENSIONS OF HEXAGON KEYS AND BITS
Nominal Key or Bit and Socket Size		Hexagon Width Across Flats W		Hexagon Width Across Corners Y [Note (2)]		Length of Short Arm B		Length of Long Arm C				Minimum Radius of Bend R	Length of Bit, +0.062 L [Note (3)]	Maximum Chamfer, K [Note (4)]
		Hexagon Width Across Flats W		Hexagon Width Across Corners Y [Note (2)]		Length of Short Arm B		Short Series		Long Series
		Max.	Min.	Max.	Min.	Max.	Min.	Max.	Min.	Max.	Min.
... ... ... 1/16	0.028 0.035 0.050 0.062	0.0280 0.0350 0.0500 0.0625	0.0275 0.0345 0.0490 0.0615	0.0314 0.0393 0.0560 0.0701	0.0300 0.0378 0.0540 0.0680	0.312 0.438 0.625 0.656	0.125 0.250 0.438 0.469	1.312 1.312 1.750 1.844	1.125 1.125 1.562 1.656	2.688 2.766 2.938 3.094	2.500 2.578 2.750 2.906	0.062 0.062 0.062 0.062	... ... ... ...	0.003 0.004 0.006 0.008

5/64 3/32 7/64 1/8	0.078 0.094 0.109 0.125	0.0781 0.0937 0.1094 0.1250	0.0771 0.0927 0.1079 0.1235	0.0880 0.1058 0.1238 0.1418	0.0859 0.1035 0.1210 0.1390	0.703 0.750 0.797 0.844	0.516 0.562 0.609 0.656	1.969 2.094 2.219 2.344	1.781 1.906 2.031 2.156	3.281 3.469 3.656 3.844	3.094 3.281 3.469 3.656	0.078 0.094 0.109 0.125	... ... ... ...	0.008 0.009 0.014 0.015

9/64 5/32 3/16 7/32	0.141 0.156 0.188 0.219	0.1406 0.1562 0.1875 0.2187	0.1391 0.1547 0.1860 0.2172	0.1593 0.1774 0.2135 0.2490	0.1566 0.1745 0.2105 0.2460	0.891 0.938 1.031 1.125	0.703 0.750 0.844 0.938	2.469 2.594 2.844 3.094	2.281 2.406 2.656 2.906	4.031 4.219 4.594 4.969	3.844 4.031 4.406 4.781	0.141 0.156 0.188 0.219	... ... ... ...	0.016 0.016 0.022 0.024

1/4 5/16	0.250 0.312	0.2500 0.3125	0.2485 0.3110	0.2845 0.3570	0.2815 0.3531	1.219 1.344	1.031 1.156	3.344 3.844	3.156 3,656	5.344 6.094	5.156 5.906	0.250 0.312	... ...	0.030 0.032
Cam-Tech Industries uses up to 5/16" key only.

NOTES:
(1) Hexagon Keys are furnished as Short Arm Series or Long Arm Series.
(2) Any truncation or rounding of hexagon comers within the specified across-corner dimensions shall be evident on all corners.
(3) For nominal socket sizes above 1 in., it is recommended that bits be used in conjunction with standard hexagon wrenches or power drives. When the application makes the use of keys necessary, the keys should conform to the dimensions listed. Bits 1 in. and smaller are available, but the lengths have not been standardized.
(4) Each end shall be square with the axis of each arm within 4 deg and edges may be sharp or chamfered at the option of the manufacturer. The chamfer shall not exceed the values listed.
(5) Material (Steel Alloy). Hexagon keys and bits shall be fabricated from an alloy steel having two or more of the following alloying elements: chromium, nickel, molybdenum, or vanadium, in sufficient quantity to ensure that the specified minimum hardness of 48 HRC at the surface for nominal sizes up to and including 3/8 in., and 45 HRC for nominal sizes over 3/8 in., is met when hexagon keys and bits are hardened by quenching from the austenitizing temperature and tempered.
(6) For plated hexagon keys and bits, all dimensions are before plating. Because of the high hardness of these products, it is recommended that they not be electroplated.
(7) For applicability of keys and bits to various socket screw types and sizes, see Nonmandatory Appendix B, Table B-1.
(8) Designation. To promote uniformity and understanding in communications relating to products conforming to this Standard, it is recommended that Hexagon Keys or Bits be designated in accordance with the following data, preferably in the sequence shown: (a) product name (b) designation of the standard (c) nominal key or bit size (d) series (e) protective finish, if required
EXAMPLES:
Hexagon Key, ASME B18.3, '/, Short Arm Series
Hexagon Key, ASME B18.3, 1/8 Long Arm Series, Nickel Plated. [See Note (6).]
Hexagon Key Bit, ASME B18.3, 11/2 Hex

TABLE 8 DIMENSIONS OF HEXAGON KEYS AND BITS