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measuring_fasteners_screws


 

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.

round headed screw

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

countersunk screw

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.

 

Hex Bolts

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

 

hex bolt

 

Wood Screws

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

  • Countersunk (Flat or Oval head) are
    measured overall.

 

flat headed wood screw         
oval head wood screw

 

  • Round head screws are measured from
    under the head.

 

round head wood screw

 

Machine Screws

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

  • Countersunk (Flat or Oval head) is
    measured overall.

 

flat head machine screw       
oval head machine scew

 

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

 

pan head machine screw      
round head machine screw

 

Carriage Bolts

Carriage bolts are measured from directly
under the head.

 

carriage bolt

 

Lag Bolts (Lag Screws)

Lag Bolts are measured from under the
head.

 

lag bolt or lag screw

 

Sheet Metal Screws

Sheet metal screw measurement depends upon
the type of screw you are using.

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

 

flat head sheet metal screw      
oval head sheet metal screw

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

 

pan head sheet metal screw      
hex head sheet metal screw

 

Socket Products

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

  • Flat Socket Caps are measured by the
    overall length.

 

flat socket cap

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

 

socket head cap            
button head caps

 

Eye Bolts

Eye Bolts are measured from under the eye.

 

eye bolt          
eye bolt

 

 eye bolt         
eye bolt

 

Hanger Bolts

Hanger bolt length is measured from end to end.

hanger bolt

 

Shoulder Bolts

Shoulder bolt length is measured as the
length of the shoulder.

shoulder bolt

 

Sex Bolts

Sex bolt length is measured from under the
head.

sex  bolt

 

 

 

This is just one of the very useful
articles featured on the site of

https://www.boltdepot.com

others include 


Metric
Tap and Drill Bit Size Table


US
to Metric Conversion Table


 

 

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