Hex bolts are bolts with a hexagonal head on one end, with no washer face on the bearing surface, and a threaded shaft on the other end; hex bolts are tightened with a wrench, they are used to connect metal parts. (The body tolerances of hex bolts are not as close as those of hex cap screws.)
Also known as the Hex Head Bolts, the Hex Head Machine Bolts, or Machine Bolts, Hex Bolts offer easier wrenching than square bolts, and is much more common in present-day applications. Sizes run from ¼-20 to 2-4. Machine bolt shafts may be partially threaded or fully threaded.
Basic thread length equals twice the bolt diameter (size) plus 1/4 inch for machine bolt lengths up to and including 6 inches, and twice the bolt diameter plus 1/2 inch for lengths over 6 inches.
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Hex Machine Bolt Dimensions s
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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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|
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Max
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Min
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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
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.26
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.237
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7/16
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.505
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0.484
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11/64
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0.75
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1.00
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5/16
|
.324
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.298
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1/2
|
.577
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0.552
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7/32
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0.88
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1.13
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3/8
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.388
|
.360
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9/16
|
.650
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0.62
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1/4
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1.00
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1.25
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7/16
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.452
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.421
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5/8
|
.722
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0.687
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19/64
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1.13
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1.38
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1/2
|
.515
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.482
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3/4
|
.866
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0.826
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11/32
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1.25
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1.50
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5/8
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.642
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.605
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15/16
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1.083
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1.033
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27/64
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1.50
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1.75
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3/4
|
.768
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.729
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1-1/8
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1.299
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1.24
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1/2
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1.75
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2.00
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7/8
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.895
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.852
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1-5/16
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1.516
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1.447
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37/64
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2.00
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2.25
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|
1
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1.022
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.976
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1-1/2
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1.732
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1.653
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43/64
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2.25
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2.50
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1-1/8
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1.149
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1.098
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1-11/16
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1.949
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1.859
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3/4
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2.50
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2.75
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1-1/4
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1.277
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1.223
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1-7/8
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2.165
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2.066
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27/32
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2.75
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3.00
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1-3/8
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1.404
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1.345
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2-1/16
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2.382
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2.273
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29/32
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3.00
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3.25
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1-1/2
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1.531
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1.47
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2-1/4
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2.598
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2.48
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1
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3.25
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3.50
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1-3/4
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1.785
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1.716
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2-5/8
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3.031
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2.893
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1-5/32
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3.75
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4.00
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2
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2.039
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1.964
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3
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3.464
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3.306
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1-11/32
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4.25
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4.50
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2-1/4
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2.305
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2.214
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3-3/8
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3.897
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3.719
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1-1/2
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4.75
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5.00
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2-1/2
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2.559
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2.461
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3-3/4
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4.33
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4.133
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1-21/32
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5.25
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5.5
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2-3/4
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2.827
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2.711
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4-1/8
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4.763
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4.546
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1-13/16
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5.75
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6.00
|
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3
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3.081
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2.961
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4-1/2
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5.196
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4.959
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2
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6.25
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6.50
|
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3-1/4
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3.335
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3.21
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4-7/8
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5.629
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5.372
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2-3/16
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6.75
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7.00
|
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3-1/2
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3.589
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3.461
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5-1/4
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6.062
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5.786
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2-5/16
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7.25
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7.50
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3-3/4
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3.858
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3.726
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5-5/8
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6.495
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6.198
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2-1/2
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7.75
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8.00
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4
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4.111
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3.975
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6
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6.928
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6.612
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2-11/16
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8.25
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8.50
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(Standards set by American Society of Mechanical Engineering)
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