PRODUCT USER GUIDE: Measuring a screw

Choosing the right screw dimensions for the work and assemblies you are carrying out is the first step in selecting the right screw. Using your assembly and set screws correctly requires a length and diameter that match your fixing support. The way to measure a screw can vary and is not always the same for every screw type. To help you, Ajile explains in its product user guide for screws how to measure the length and diameter of a plastic screw.

Measuring the length of a screw

The screw length depends on your fixing. For small screws, it is commonly recommended to use a screw three times the thickness of the part being fixed. For long screws, twice the thickness of the part being fixed is enough to ensure strength and durability. Measuring the length of a screw follows different techniques and standards depending on the head type.
To measure a countersunk head screw as well as a hex head screw, the entire component is taken into account, from the tip to the top of the head.
The measurement of a round head screw and a flange head screw is taken from the tip of the screw to the end of the flange, under the head.

Ajile offers a wide selection of plastic screws: countersunk head screws, round, hex head, knurled and headless are available in different lengths to give you all the options you need for your fixing and assembly work.

You will find them sorted by diameter, in lengths from 5 mm for the screws with the smallest diameters (M2 screws; M2.5 screws) up to 80 mm for screws with larger diameters (M12 screws).

Measuring the diameter of a screw

In addition to the screw length, which is important to hold the part to be fixed and ensure good strength, choosing the screw diameter is also essential to avoid damaging the support and to guarantee the part is held securely. The diameter of a screw is measured at the thread, not on the shank. There are different thread types. Metric thread is the most common and widely used; it is expressed in millimeters and is associated with the letter M. The screw diameter is therefore given after this letter. A 10 mm screw will be обозначated as “M10”.
The metric thread therefore defines the diameter of a screw.

Measuring the thread of a screw

To measure the thread of a screw and determine the thread pitch, you need to consider the length of the screw from the first thread to the last thread, as well as the number of threads. The screw length must be divided by the total number of threads minus one thread. This calculation gives the thread pitch for a coarse pitch (standard screw pitch).
For example, a nylon screw with a length of 79 mm from the first thread to the last thread, counting 80 threads, will have a thread pitch of 1 mm - (79/(80-1)).

On the ajile.biz website, you will find different ranges of screws sorted by their metric thread, from M2 to M10 plastic screws for round heads and countersunk heads, and from M2 to M12 plastic screws for hex heads. Headless screws are offered in M3, M4, M5, M6, M8 and M10.

Want to learn more about plastic fasteners?

Our website, specialized in the sale of plastic fasteners and plastic hardware, provides all the information you need for your online purchase and remains available for personalized advice. Find all details about our plastic fasteners and their technical characteristics in the dedicated pages.

Choose online purchase of plastic screws on ajile.biz, the reference site for plastic components!

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