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

Carriage bolt diameter

Diameter and Thread count

Matching Products

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Prod. # Description Buy
9480
USS flat washers, Chrome plated steel, 5/16"
USS pattern is the most common type of flat washer.
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$1.26 / ea
$10.55 / 10
$97.10 / 100
9493
Lock washers, Chrome plated steel, 5/16"
Split lock washers place tension against a nut after tightening, to help prevent loosening.
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$1.58 / ea
$12.73 / 10
$117.00 / 100