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.
Add
$0.11 each
$6.85 / 100
$60.90 / 1000
3061
USS flat washers, Zinc plated grade 8 steel yellow, 5/16"
USS pattern is the most common type of flat washer.
Add
$0.13 each
$7.60 / 100
$64.00 / 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.
Add
$0.05 each
$3.09 / 100
$27.60 / 1000

See also

Metric hex bolt

Metric hex bolts

A bolt with a six sided head.