HOW TO MEASURE FASTENER/SCREW LENGTHS
Reproduced by kind permission of www.boltdepot.com
Fastener length is measured from where the material surface is assumed to be, to the end of the fastener.
Hex bolts are measured from under the head to the tip of the bolt.
Wood screw measurement depends upon the type of screw you are using.
Machine screw measurement depends on the style of head it has.
Carriage bolts are measured from directly under the head.
Lag Bolts (Lag Screws)
Lag Bolts are measured from under the head.
Sheet Metal Screws
Sheet metal screw measurement depends upon the type of screw you are using.
Socket screw measurement depends upon the type of screw you are using.
Eye Bolts are measured from under the eye.
Hanger bolt length is measured from end to end.
Shoulder bolt length is measured as the length of the shoulder.
Sex bolt length is measured from under the head.
Here’s a formula sent in by Geoff Sharpe, for working out the exact diameter, in inches, of the shank of a screw.
Multiply the screw Number by 13 and add “.060.
(No.) 8 x 13 + “.060 = “.164
(No.)10 x 13 + “.060 = “.190