mesure

Measuring Tips

We receive a lot of questions on measuring, Thread
pitch and the like.
I hope what we posted below helps.

The socket the bolt uses does not determine the bolt sizeAll standard bolts are
measured from the end of the threads to the bottom of
the bolt head. The bolt head makes no difference in general measurements.

All standard bolts are measured from the end of the threads to the bottom of
the bolt head. The bolt head makes no difference in general measurements.

Pitch

Here is a list of
common thread
pitches in my store:

M4=0.7
M5=0.8
M6=1.0
M8=1.25
M10=1.5

All bolts are these
pitches unless
otherwise specified

Example: M8x30
Non-Taper Head

The example to the
left shows an M8x30.

30mm does not
include the head
height.

8mm is the width of
the shaft, NOT the
size of the allen socket

Countersunk Bolts

Example: M5x20
Countersunk

Pitch

Here is a list of
common thread
pitches in my store:

M4=0.7
M5=0.8
M6=1.0
M8=1.25
M10=1.5

All bolts are these
pitches unless
otherwise specified

The example to the
left shows an M5x20.

head height.

5mm is the width of
the shaft, NOT the size
of the allen socket.

Check the photos
below for the
measurements of
Chainring bolts

A 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. Our button head and socket head cap screws are measured in this way.
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. Our flat head screws are measured in this way.

US Fasteners
US Fasteners are described by the diameter, thread count (machine threads only) and length.
The diameter and length are in inches with the exception of small screws whose diameter may be
a size number (ex. 12). In
this case the number will often have a # sign before it (ex. #12)
Example:
1/4-20 x 6
This has a diameter of 1/4 inch, 20 threads per inch (course thread) and a length of 6 inches.

Metric Fasteners
Metric fasteners are described in a similar manner to US fasteners. However, instead of threads
per inch, the metric system
uses thread pitch (the length of each thread in millimeters measured along the shaft of the bolt).
Typically the diameter of a
metric bolt is preceded by a capital M to designate metric.
Example:
M10 x 1.5 x 20
This has a diameter of 10mm, a 1.5 thread pitch and measures 20mm long.