Machine Screw Dimensions
Need dimensions? We've got'em - right out of the Industrial Fasteners Institute Fastener Standards , Sixth Edition! If all you want to do is determine what size fastener you have, might I suggest our nifty thread gage ( DG-0014) instead? It's a lot easier!
 |
| Length Tolerance |
Up to and Including 3/4”
|
-.03” |
Over 3/4”, up to 1-1/2” Included
|
-.05” |
| Over 1-1/2” |
-.06” |
| Size |
"A" Flat and Pan |
"B" Flat Head |
"B" Pan Head |
"C" Pan Head |
| Max |
Min |
Max |
Min |
Max |
Min |
Max |
Min |
| 6-32 |
.137 |
.131 |
.279 |
.244 |
.270 |
.256 |
.097 |
.087 |
| 8-32 |
.163 |
.157 |
.332 |
.292 |
.322 |
.306 |
.115 |
.105 |
| 10-24 |
.189 |
.181 |
.385 |
.340 |
.373 |
.357 |
.133 |
.122 |
| 10-32 |
.189 |
.183 |
.385 |
.340 |
.378 |
.357 |
.133 |
.122 |
| 1/4-20 |
.249 |
.236 |
.507 |
.452 |
.492 |
.473 |
.175 |
.162 |
To convert the decimal dimensions shown above to fractional dimensions, simply multiply by 64. The result will be the number of 64ths of an inch equal to the decimal dimension. For instance, the thread size on a 1/4-20 screw is given as .249”. Converting to a fraction, multiply by 64 (.249 x 64=15.936). The answer, 15.936, rounds to 16/64, or 1/4 of an inch. McFeely's Metric Conversion Chart