Metric thread - field of application and application methods

One of the most common in industry and at home is metric carving. It is used in most fasteners. It has a profile in the form of an equilateral triangle, all dimensions are measured in millimeters.

Thread metric - basic dimensions

The indicated thread is indicated by the letter "M" and the numbers that denote the diameter of the rod. Thus, the designation M8 indicates that the product is marked with a metric thread and the diameter of the rod is 8 mm.

Another indicator of such a thread is its step, which is indicated after the first digit and the sign "x." Large steps are usually not written, since they are basic, the step itself is the distance between the vertices of the turns that are located side by side. Experienced masters define a step by step, as well as there are special templates, which are called threadmakers.

If the bolt has a metric thread and you need to determine its step, and there is no threadmeter on hand, this can be done with any measuring device, for example, a caliper, but you can use a locksmith. To do this, measure the distance between several turns, and then divide the resulting number by their number.

The determination of the thread pitch is necessary for various operations, for example, for the correct selection of a threading tool or a drill. Since during the threading of the rod, the metal is pulled out, then take a rod slightly smaller in diameter than the required thread size.

There are times when it is necessary to make a hole for the thread to be cut, but there are no necessary directories. This problem can be dealt with using simple mathematical calculations. For example, you need to drill a hole for thread diameter of 14 mm. We found that the thread pitch is 1 mm, then 14 - 1 = 13. That is, the diameter of the hole in which the metric thread will be cut should be 13 mm.

A metric tapered thread that has a taper of 1:16 is usually used for conical joints, and an outer tapered thread with an internal cylindrical thread can also be connected.

Cutting metric threads can be done in several ways, for example, on a lathe or drilling machine, on special thread cutting machines , and can also be done manually. When manually threading the rod, a die is used, tapping is used to cut the internal thread.

In the latter case, taps of several sizes are used. The first and second numbers are pre-cut, and the third is given the final shape and size. Only two sizes can be used - a finishing and a rough tap. They are made of strong, high-carbon steels.

Plates can be either round or sliding, they are also called prismatic. When using round dies, they are preliminarily clamped into the wrenches, and then threaded by the external thread.

We cut the internal thread

First you need to prepare a hole. For better cutting, it is necessary for the drill to have a slightly larger diameter than the inner diameter of the future thread. If you make a hole that is equal to the internal diameter of the thread, then when it is cut, the metal particles to be removed will strongly press the tap teeth and cause it to overheat. The result of this will be a poor-quality thread with torn combs, as well as a tool breakage.

When cutting the external thread with a plate, problems usually do not arise. From the very beginning it is necessary to accurately expose the workpiece and the tool, then you will get a quality thread.