Screw marking

When choosing the right screw, basic information about it is an important factor. In addition to the type of screw we choose, we should consider the type of thread, strength class, as well as thickness and length.

Of course, each bolt feature is properly described and so the thickness is expressed via “M”, and the type of head is determined by the standard expressed most often via the DIN marking. There are as many markings as there are types of bolts, but for the example DIN 603 means a mushroom head bolt, and DIN 933 is a hexagonal head bolt. An example of a full bolt marking may look like this: DIN 933 M10x100, where x100 at the end is on its own information about the length of a given bolt, given in millimeters. An exemplary bolt may be of various sizes, but the standard size ranges from 8mm to 260mm, although of course there are exceptions.

As for the accuracy of execution, we can distinguish the following bolts:

• Raw (plain), marked with the symbol C and usually made with a hexagonal head, square head, and also with a smooth cylindrical shank.
• Medium, marked with the symbol B
• Fine, marked with the symbol A
• Shoulder bolts, characterized by a smaller diameter of the threaded section than the smooth section, most often mounted in small holes by tapping with a hammer. However, this type is rarely used nowadays.

The last type of screws are bolts for pre-stressed connections, made as grade B, but made of very high-strength steel. Such a bolt is often made with traditional shapes and used in pre-stressed butt joints.