Measuring thread pitch

How to measure thread pitch



threadpitch

Why do i need to measure thread pitch?


Measuring thread pitch is important if you are a machinist and need to recreate the thread. When copying an existing thread you must have the same thread. It is also important when purchasing bolts and nuts to have the correct pitch. For example 1/4" bolts come in two different pitches. There is 1/4" - 20 UN (this is the most common). Then there is 1/4" - 28 UNF (this is the fine version).

Here i will teach you three ways you can measure thread pitch.

Step 1 - Using a pitch gauge
A pitch gauge is a comparative measuring tool that has all the standard thread pitches cut into fingers to align against an existing thread. Gauges come in inch and metric sets.

Here is a set of inch and metric pitch gauges. These have most standard sizes of each thread. Some gauges have many more size ranges.
pitch gauge

Measuring the pitch is done by aligning the finger up to the thread like the photo below. To get the more accurate results it is important to have a clean thread and put the gauge in front of a light.
pitch gauge

Step 2 - Direct measuring
This method is not the most accurate and should only be used when you do not have a gauge. You can determine the thread pitch by measuring the distance between the crest (the top part of the thread).
Using a caliper measure the distance between the crests. As seen in the image below the approx pitch is 0.060" or 16 Threads per inch.
measuring pitch with caliper

Step 3 - Compare to known pitch
The quickest way to determine the pitch can be done by comparing the thread to a known thread pitch. All you have to do is take your known pitch thread and place it against your sample thread. As seen in the image below the two threads match perfectly.
comparing threads