Screws - the length

Screws are really available in all imaginable versions and variations. The length of the screw and other dimensions are of great importance. However, there are small differences in measuring the length of a screw, depending on the type of screw and use.

Technical distinction of screws

Basically, two major distinctions can be made with screws that already say a lot. Distinguish the screws as follows:

  • cylindrical screws requiring a counter thread (mostly metric screws)
  • conical or tapered screws that cut the mating thread itself

The length of a screw can be measured differently

But to measure a screw, other information is important. Screws for countersinking are measured differently than screws whose head is not sunk in the workpiece. A concrete example is the countersunk screw. Note, however, that even screws with a cylindrical head can be quite sunk.

Countersunk or not countersunk screw is important for length measurement

Why this distinction is so important becomes clear quickly. Screws that are countersunk are completely screwed or screwed into the workpiece from the tip to the screw head. For all other workpieces, the screw head is on the other hand. Important for the length of the screw, however, is the screw-in length or insertion length. Therefore, screws that are countersunk are measured in absolute length and all other screws from below the screw head to the top of the thread.

You have to differentiate again. Between screws that are specifically made to sink completely and other screws that can be sunk, but not necessarily be sunk. Special countersunk screws are always measured in absolute length. All other screws, however, individually as they are used.

The knife the length of screws

To measure the screw length you need a caliper. The length is then determined and specified in millimeters. Unscrewed screws are measured without a head and all others with a screw head.

Measuring the screw size (cross section)

This number is important because it is always given together with the length of a screw. The size of the screw is measured by placing the screw lengthways between the jaws of the caliper. The measurement is therefore not transverse to it! Otherwise, there is a risk that the screw in the jaws of the caliper will tilt.

Length examples of screws

A typical screw size would be 5 times 60. A screw with these dimensions has a size (cross section) of 5 mm and a length of 20 mm. Screws are always offered in certain gradations. If you need an "intermediate size", it may be possible that you need to cut these screws.

Tips & Tricks

Besides these dimensions, other values ​​are important. So there are great differences in the threads (regular or fine thread or thread pitch). In addition, screws have different hardnesses depending on the manufacturing process and selected metal alloy.

Video Board: How to Choose the Right Screws