Measuring Fastener Length
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 | Wood Screws | Machine Screws | Carriage
Bolts | Lag Bolts (Lag Screws) | Sheet
Metal Screws | Socket Products | Eye Bolts | Hanger Bolts
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 head) 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 head) are measured by overall
length.
 
- Pan Head, truss head, and Hex Head screws are measured from
under the head.
 
Socket 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.
 
Eye Bolts
Eye Bolts are measured from under the eye.
 
 
Hanger Bolts
Hanger bolt length is measured from end to end.
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