ASME B18.8.1 Cotter Pins

ASME B18.8.1 Cotter Pin

Dimensions of ASME B18.8.1 Cotter Pin

Nominal Size or Basic Pin Diameter A B C D Gage Hole Diameter +-0.001
Total Shank Diameter Wire Width Head Diameter Extended Prong Length
Max Min Max Min Min Min
1/32 0.031 0.032 0.028 0.032 0.022 0.06 0.01 0.047
3/64 0.047 0.048 0.044 0.048 0.035 0.09 0.02 0.062
1-16 0.062 0.060 0.056 0.060 0.044 0.12 0.03 0.078
5/64 0.078 0.076 0.072 0.076 0.057 0.16 0.04 0.094
3/32 0.094 0.090 0.086 0.090 0.069 0.19 0.04 0.094
3/32 0.094 0.090 0.086 0.090 0.069 0.19 0.04 0.109
7/64 0.109 0.104 0.100 0.104 0.080 0.22 0.05 0.125
1/8 0.125 0.120 0.116 0.120 0.093 0.25 0.06 0.141
9/64 0.141 0.134 0.130 0.134 0.104 0.28 0.06 0.156
5/32 0.156 0.150 0.146 0.150 0.116 0.31 0.07 0.172
3/16 0.188 0.176 0.172 0.176 0.137 0.38 0.09 0.203
7/32 0.219 0.207 0.202 0.207 0.161 0.44 0.10 0.234
1/4 0.250 0.225 0.220 0.225 0.176 0.50 0.11 0.266
5/16 0.312 0.280 0.275 0.280 0.220 0.62 0.14 0.312
3/8 0.375 0.335 0.329 0.335 0.263 0.75 0.16 0.375
7/16 0.438 0.406 0.400 0.406 0.320 0.88 0.20 0.438
1/2 0.500 0.473 0.467 0.473 0.373 1.00 0.23 0.500
5/8 0.625 0.598 0.590 0.598 0.472 1.25 0.30 0.625
3/4 0.750 0.723 0.715 0.723 0.572 1.50 0.36 0.750
See Notes 1,2 3

NOTES.
(1) Where specifying nominal size in decimals, zeros precedin9 the decimal shall be omitted.
(2) 5/64, 7/32, and 3/4 not preferred for new design.
(3) Total shank diameter, A, dimension is two times wire thickness. A is measured at end of pin where no gap is permitted.
(4) For additional requirements, refer to General Data for Cotter Pins, page L-34.

ASME B18.8.1 Cotter Pin

Cotter Pin Length Gage

The Tolerance on length of cotter pins shall be tabulated below:

Nominal Pin Length Tolerance on Length
Up to 1 in. ± 0.03
1 in. and longer ± 0.06

Preferred Sizes and Lengths of Extended Prong Type Cotter Pins

Nominal Pin Length Nominal Pin Size
1/32 3/64 1/16 3/32 1/8 5/32 3/16 1/4 5/16 3/8 1/2 5/8
1/2 XX XX XX XX XX
3/4 XX XX XX XX XX XX XX
1 XX XX XX XX XX XX XX XX XX
1-1/2 XX XX XX XX XX XX XX XX
2 XX XX XX XX XX XX XX XX
2-1/2 XX XX XX XX XX XX XX XX
3 XX XX XX XX XX XX XX XX
3-1/2 XX XX XX XX XX XX
4 XX XX XX XX XX XX
5 XX XX XX XX
6 XX XX XX

Preferred Sizes and Lengths of Hammer Lock Type Cotter Pins

Nominal Pin Length Nominal Pin Size
3/64 1/16 3/32 7/64 1/8 5/32 3/16 1/4 5/16 3/8
1/2 XX XX XX XX XX
3/4 XX XX XX XX XX XX XX
1 XX XX XX XX XX XX XX XX
1-1/2 XX XX XX XX XX XX XX XX XX
2 XX XX XX XX XX XX XX XX XX
2-1/2 XX XX XX XX XX
3 XX XX XX XX XX
3-1/2 XX XX XX XX
4 XX XX XX XX

Material
Low carbon steel. When so specified by purchaser, pins may also be made from ASTM A493, Types 302 (UNS S30200) and 304 (UNS S30400), corrosion resistant steel; ASTM 8134, Alloy 260 (UNS C26000), cartridge brass; Monel Alloy (UNS N04400) or other material as agreed upon between manufacturer and purchaser.

Desgination
Cotter pins shall be designated by the following data, in sequence shown:
(a) product name (noun first);
(b) nominal size (fraction or decimal equivalent).
(c) pin length;
(d) poinl type;
(e) material and protective finish, if required.
EXAMPLES:
P-in, Cotter, 1/8 x 1-1 /4, Extended Prong Type, Steel, Zinc Plated
Pin, Cotter, 0.250 x 1.50, Hammer Lock I Type, Corrosion Resistant Steel