Hex Cap Bolt Dimensions

Hex cap bolt dimensions are trickier than you think.  By default, they are not threaded all the way, so you need to be careful in your design to make sure you are not threading beyond the capability of the bolt itself.

Just as with the standard nut and washer, it it important to consider the geometric constraints of the hex cap bolt to ensure proper function and easier assembly / disassembly.


Hex Bolt Dimensions s
Basic Product Diameter
Full-Size Body Diameter
Width Across Flats
Width Across Corners
Head Height
Thread Length
Thread Length
Max
Min
Max
Min
Up to 6in
Over 6 in
1/4
.26
.237
7/16
.505
0.484
11/64
0.75
1.00
5/16
.324
.298
1/2
.577
0.552
7/32
0.88
1.13
3/8
.388
.360
9/16
.650
0.62
1/4
1.00
1.25
7/16
.452
.421
5/8
.722
0.687
19/64
1.13
1.38
1/2
.515
.482
3/4
.866
0.826
11/32
1.25
1.50
5/8
.642
.605
15/16
1.083
1.033
27/64
1.50
1.75
3/4
.768
.729
1-1/8
1.299
1.24
1/2
1.75
2.00
7/8
.895
.852
1-5/16
1.516
1.447
37/64
2.00
2.25
1
1.022
.976
1-1/2
1.732
1.653
43/64
2.25
2.50
1-1/8
1.149
1.098
1-11/16
1.949
1.859
3/4
2.50
2.75
1-1/4
1.277
1.223
1-7/8
2.165
2.066
27/32
2.75
3.00
1-3/8
1.404
1.345
2-1/16
2.382
2.273
29/32
3.00
3.25
1-1/2
1.531
1.47
2-1/4
2.598
2.48
1
3.25
3.50
1-3/4
1.785
1.716
2-5/8
3.031
2.893
1-5/32
3.75
4.00
2
2.039
1.964
3
3.464
3.306
1-11/32
4.25
4.50
2-1/4
2.305
2.214
3-3/8
3.897
3.719
1-1/2
4.75
5.00
2-1/2
2.559
2.461
3-3/4
4.33
4.133
1-21/32
5.25
5.5
2-3/4
2.827
2.711
4-1/8
4.763
4.546
1-13/16
5.75
6.00
3
3.081
2.961
4-1/2
5.196
4.959
2
6.25
6.50
3-1/4
3.335
3.21
4-7/8
5.629
5.372
2-3/16
6.75
7.00
3-1/2
3.589
3.461
5-1/4
6.062
5.786
2-5/16
7.25
7.50
3-3/4
3.858
3.726
5-5/8
6.495
6.198
2-1/2
7.75
8.00
4
4.111
3.975
6
6.928
6.612
2-11/16
8.25
8.50