How to measure screw size

Editor:Jiaxing UNITEK Machinery Technology Co., Ltd. │ Release Time:2021-11-11 

Screws are connecting fasteners that are inseparable from all major fields. Many major accidents are caused by the failure of fasteners, and it can be seen that small fasteners play an important role in the entire system. Therefore, the size of each screw must be strictly controlled within the error range. But many people don’t know how to measure the size of a screw, and even measure it directly with an ordinary ruler or even a tape measure. This is very unprofessional. For these small and precise products, we need to use professional Vernier calipers and micrometers to measure, so how to measure the most accurate?

Diameter measurement:

The diameter of the screw refers to the screw part of the screw, but the screw has a distinction between full thread and half thread. It is fine to measure the middle of the screw directly with full thread, and the polished rod part needs to be measured for half thread. The measurement methods are as follows:



Head thickness measurement:

We usually need to measure the head of screws, generally only flat head screws and hexagonal screws, other head types are generally produced according to standards.


Head size measurement:

Generally, screws must be tested for head size, especially non-standard parts and special-shaped parts.


Hexagonal side measurement:

The outer hexagonal screws need to measure the size of the opposite side and the size of the opposite corner.


Length measurement:

There are also two types of screw length measurement. One is the measurement of countersunk head screws: a whole screw from the head to the tail; while the other screws are from the head to the tail.


Groove depth measurement:

The measurement of groove depth is also indispensable. The groove depth of non-standard parts can be changed according to customer requirements.