HOW TO MEASURE 
FASTENER/SCREW LENGTHS

Reproduced by kind permission of www.boltdepot.com

General

Fastener length is measured from where the material surface is assumed to be, to the end of the fastener.

• For fasteners where the head usually sits above the surface the measurement is from directly under the head to the end of the fastener.    

• For fasteners that are designed to be countersunk, the measurement is made from the point on the head where the surface of the material is, to the end of the fastener.

Specific Types

Hex Bolts

Hex bolts are measured from under the head to the tip of the bolt.

 

Wood Screws

Wood screw measurement depends upon the type of screw you are using.

 

Countersunk (Flat or Oval head) are measured overall.

 

Round head screws are measured from under the head.

 

 

Machine Screws

Machine screw measurement depends on the style of head it has.

Countersunk (Flat or Oval) is measured overall.

 

Pan Head or Round Head screws are measured from under the head.

 

 

 

Carriage Bolts

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.

 

Countersunk screws (Flat or Oval) are measured by overall length.

 

Pan Head, truss head, and Hex Head screws are measured from under the head.

 

 

 

 

Socket Head Products

Socket screw measurement depends upon the type of screw you are using.

 

Flat Socket Caps are measured by the overall length.

 

Socket Head Caps and Button Head Caps are measured from under the head.

 

This is just one of the very useful articles featured on the site of www.boltdepot.com

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.

Examples -  

(No.) 8 x 13 + ".060 = ".164

(No.)10 x 13 + ".060 = ".190

 

           

Copyright © 2000-2008 Hints and Things
All Rights Reserved.

No portion of this site may be reproduced or redistributed without prior written permission from Hints and Things. All trademarks & copyrights throughout Hints and Things remain the property of their respective owners.

Hints and Things cannot be held responsible for any information given on this site nor do they necessarily agree with, or endorse, the views given by third parties.