Parallel pins m6 DIN 7A-stainless A4 3 m6x20

The tolerance grade is indicated by numbers ranging from 1 to 18. As the number increases, the size of the tolerance zone increases. The size of the tolerance depends on the nominal dimension. The tolerance system for internal and external dimensions is standardised in accordance with DIN EN ISO 286. The tolerance zones for external dimensions are indicated by lower-case letters followed by numbers.

Grade 1.4571 is an austenitic stainless steel of the A5 type. It has the properties of the A4 type, but with improved temperature resistance. The A5 grade is stabilised by the addition of titanium. This prevents intergranular corrosion. The material has good forgeability, excellent weldability and poor machinability. It does not exhibit brittle fracture behaviour and can therefore be used at low temperatures.

Stainless steel refers to alloyed or unalloyed steels that contain at least 10.5% chromium and less than 1.2% carbon. Colloquially, stainless steel is also referred to as stainless steel (NiRo), although not all stainless steel is the same as "stainless".

The term plain indicates a completely untreated, merely oiled, smooth surface for all DIN and ISO screws such as wood screws, hexagon head screws, threaded rods, nuts and many types of washers.

Stainless steels are defined in DIN EN 10088-1 as iron alloys containing at least 10.5 per cent chromium and no more than 1.2 per cent carbon. The multi-part DIN EN ISO 3506 series of standards applies to mechanical fasteners made from stainless steels. Grade A4 is classified as acid-resistant due to its molybdenum content of 2 per cent to 3 per cent. A4 cannot be heat-treated and achieves its various strength classes through cold working to different degrees.