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Hex Bolt Dimensions, Sizes, Threads per Inch, Head
Dimensions & Minimum Threaded Length
Nominal Size Threads
per Inch		 Head Width Head
Height		 Minimum
Threaded
Length
Across
Flats		 Across
Corners
Fraction Decimal UNC UNF Basic Avg Basic ≤6" >6"
1/4 0.2500 20 28 7/16 1/2 5/32 3/4 1
5/16 0.3125 18 24 1/2 9/16 13/64 7/8 1 1/8
3/8 0.3750 16 24 9/16 41/64 15/64 1 1 1/4
7/16 0.4375 14 20 5/8 45/64 9/32 1 1/8 1 3/8
1/2 0.5000 13 20 3/4 55/64 5/16 1 1/4 1 1/2
9/16 0.5625 12 18 13/16 59/64 23/64 1 3/8 1 5/8
5/8 0.6250 11 18 15/16 1 1/16 25/64 1 1/2 1 3/4
3/4 0.7500 10 16 1 1/8 1 9/32 15/32 1 3/4 2
7/8 0.8750 9 14 1 5/16 1 31/64 35/64 2 2 1/4
1 1.0000 8 12 1 1/2 1 45/64 39/64 2 1/4 2 1/2
1 1/8 1.1250 7 12 1 11/16 1 29/32 11/16 2 1/2 2 3/4
1 1/4 1.2500 7 12 1 7/8 2 7/64 25/32 2 3/4 3
1 3/8 1.3750 6 12 2 1/16 2 21/64 27/32 3 3 1/4
1 1/2 1.5000 6 12 2 1/4 2 17/32 1 5/16 3 1/4 3 1/2
NOTES:
1. Unless noted otherwise, all dimensions are in inches.
2. Head Width Across Corners is average size rounded to nearest 64th.
3. Actual threaded length may be longer than minimum specified for bolt
    lengths of 6 inches and less (≤6") and more than 6 inches (>6").
4. For reference only.