Hex bolt diameter is measured on the outside of the threads.

Hex bolt diameter

Diameter and Thread count

Matching Products

Click on a product # for additional info

Prod. # Description Buy
3048
SAE flat washers, Zinc plated grade 8 steel yellow, 5/16"
SAE pattern is a tighter fit on the bolt and a smaller outside diameter.
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$0.12 / ea
$7.88 / 100
$70.00 / 1000
3061
USS flat washers, Zinc plated grade 8 steel yellow, 5/16"
USS pattern is the most common type of flat washer.
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$0.15 / ea
$8.74 / 100
$73.60 / 1000
3038
Lock washers, Zinc plated grade 8 steel yellow, 5/16"
Split lock washers place tension against a nut after tightening, to help prevent loosening.
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$0.06 / ea
$3.56 / 100
$31.80 / 1000

See also

Metric hex bolt

Metric hex bolts

A bolt with a six sided head.