Screw Dimensions
| Screw dimensions. |
| We have listed our screw dimensions in two forms — a table showing the maximum and minimum decimal dimensions, and a table showing the maximum fractional dimensions. Note: The fractional dimensions are the best approximations of the actual decimal dimensions. |
 |
Screw Heads
| Decimal Dimensions |
| |
|
“A” Flat Head |
|
“A” Pan Head |
|
“A” Round Washer Head |
|
“A” Truss Head |
| Size |
|
Max |
Min |
|
Max |
Min |
|
T max |
Max |
Min |
|
T max |
Max |
Min |
| 4 |
|
0.225 |
0.195 |
|
0.219 |
0.205 |
|
0.086 |
N/A |
N/A |
|
N/A |
N/A |
N/A |
| 6 |
|
0.279 |
0.244 |
|
0.270 |
0.256 |
|
0.103 |
N/A |
N/A |
|
0.086 |
0.321 |
0.303 |
| 8 |
|
0.332 |
0.292 |
|
0.322 |
0.306 |
|
0.120 |
0.376 |
0.352 |
|
0.102 |
0.384 |
0.364 |
| 10 |
|
0.385 |
0.340 |
|
0.373 |
0.357 |
|
0.137 |
0.443 |
0.411 |
|
N/A |
N/A |
N/A |
| 12 |
|
0.438 |
0.389 |
|
0.425 |
0.407 |
|
0.153 |
N/A |
N/A |
|
N/A |
N/A |
N/A |
| 14 |
|
0.507 |
0.452 |
|
0.492 |
0.473 |
|
0.175 |
N/A |
N/A |
|
N/A |
N/A |
N/A |
| Corresponding Fractional Measurements |
| |
|
“A” Flat Head |
|
“A” Pan Head |
|
“A” Round Washer Head |
|
“A” Truss Head |
| Size |
|
Approx. Dia |
|
Approx. Dia |
|
T max |
Approx. Dia |
|
T max |
Max |
Min |
| 4 |
|
7/32 |
|
7/32 |
|
3/32 |
N/A |
|
N/A |
N/A |
N/A |
| 6 |
|
9/32 |
|
17/64 |
|
7/64 |
N/A |
|
3/32 |
21/64 |
5/16 |
| 8 |
|
21/64 |
|
21/64 |
|
1/8 |
3/8 |
|
7/32 |
25/64 |
23/64 |
| 10 |
|
25/64 |
|
3/8 |
|
9/64 |
7/16 |
|
N/A |
N/A |
N/A |
| 12 |
|
7/16 |
|
27/64 |
|
5/32 |
N/A |
|
N/A |
N/A |
N/A |
| 14 |
|
1/2 |
|
31/64 |
|
11/64 |
N/A |
|
N/A |
N/A |
N/A |
Screw Bodies/Threads
| Decimal Dimensions |
| |
|
“B” Body Dia |
|
“C” Thread Dia |
| Size |
|
Max |
Min |
|
Max |
Min |
| 4 |
|
0.095 |
0.084 |
|
0.116 |
0.105 |
| 6 |
|
0.118 |
0.107 |
|
0.142 |
0.131 |
| 8 |
|
0.136 |
0.125 |
|
0.168 |
0.157 |
| 10 |
|
0.157 |
0.146 |
|
0.194 |
0.183 |
| 12 |
|
0.176 |
0.165 |
|
0.220 |
0.209 |
| 14 |
|
0.201 |
0.190 |
|
0.246 |
0.235 |
| Corresponding Fractional Measurements |
| |
|
“B” Body Dia |
|
“C” Thread Dia |
| Size |
|
T max |
Max |
|
Max |
| 4 |
|
N/A |
3/32 |
|
1/8 |
| 6 |
|
N/A |
1/8 |
|
9/64 |
| 8 |
|
7/64 |
9/64 |
|
11/64 |
| 10 |
|
1/8 |
5/32 |
|
3/16 |
| 12 |
|
N/A |
11/64 |
|
7/32 |
| 14 |
|
N/A |
13/64 |
|
1/4 |
Screw Length
Screw lengths are measured differently depending on head type and their intended application.
- Flat head and Trim head screws are designed to be countersunk into the surface. These screws are measured from the top of the head.
- Pan head and Round Washer head screws are designed to have the head sit on top of the surface. These screws are measured from beneath the head.
| Overall Screw Length Specifications |
| Nominal Screw Length |
Tolerances |
| Plus |
Minus |
| Up to 5/8" |
0 |
0.030" |
| Over 5/8" to 1" |
0 |
0.050" |
| Over 1" to 1-1/2" |
0 |
0.050" |
| Over 1-1/2" to 2-3/4" |
0 |
0.060" |
| Over 2-3/4" |
0 |
0.090" |
|
 |
| Overall Thread Length Specifications |
Thread Length for Flat and Trim Head
(unless specified otherwise) |
|
Thread Length for Pan Head
(unless specified otherwise) |
| under 1" |
Full Thread |
|
All sizes |
Full Thread |
| 1" and over* |
2/3 Thread |
| * Note: Tolerance on thread length of 3" and longer screws is 2/3 + or - 1/4" |
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 (IC-001 and IC-002) 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" |
|
| Decimal Dimensions |
| |
|
“A” Flat and Pan |
|
“B” Flat Head |
|
“B” Pan Head |
|
“C” Pan Head |
| Size |
|
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. Also see McFeely’s Metric Conversion Chart
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