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
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||||||||
Basic Product Diameter
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Full-Size Body Diameter
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Width Across Flats
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Width Across Corners
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Head Height
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Thread Length
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Thread Length
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||
Max
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Min
|
Max
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Min
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Up to 6in
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Over 6 in
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|||
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
|