How To Measure A Bolt Diameter

Bolt Pattern Measurements Are Typically Taken In Millimeters.

Help measuring rifle bolt diameter [ re: Bolt patterns are written with 2 measurements: The scales with bolt threads come with many bolts on them.

In The Above Example, 1/2 Inch Is The Shank's Diameter.

1/4″ ‐ 20 x 3″ means 1/4″ bolt diameter with 20 threads per inch (tpi) and 3″ length. A common measurement for a 5 bolt pattern is 120 millimetres (4.7 in) from the top of 1 lug to the center of another. The length of a bolt is also stated by the measurement from under the head to the end, but the length of the thread is determined by the diameter, as shown above.

Measure The Bolt Length From Directly Under The Hex Head To The Tip Of The Bolt.

M10 x 100 bolt = 26mm thread or 1/4″unc x 2″ bolt = 3/4″ thread or 1/2″bsw x 5″ bolt = 1″ thread. D is the bolt circle diameter. The diameter of a bolt is the shank diameter, expressed in millimetres for metric bolts.

Measuring Bolts And Screws Length Is Measured From The Point At Which The Head Sits Flat With The Surface, To The Tip Of The Threads.

It is common for people to refer to hex bolts by the size of the head measured across the flats (this is also the size wrench the bolt uses). Bolts are measured in length of shank, bolt head size, width of shank (the diameter of the threaded bolt body) and the thread pitch (the size of the thread). Diameter = p/sin(180/n), where p is the distance between neighboring bolts (measured center to center), and n is the number of bolts.

How Bolt Sizes Are Expressed.

If your wheel has 5 bolts, or another odd number of bolts, measure from the very top of 1 lug nut to the center of the bolt that is directly across from it in order to find the diameter. To find each dimension, measure the following: This can be split up into two equal right angled triangles.