Hexagon nuts ~0,8d ISO 4032-stainless A5 1.4571 M20

The wrench sizes for hexagon bolts and nuts are specified in ISO 272: 1982-01. The nominal wrench size on the workpiece (e.g. bolt, nut) is the same as that on the tool. However, there is some play between the two to allow the tool to be fitted without difficulty. The relationship between the nominal diameter d of the thread and the wrench size s is standardised in EN ISO 4014 and EN ISO 4017 for hexagon bolts, and in EN ISO 4032 for hexagon nuts (dimensions in mm).

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.

Grade 1.4571 is an austenitic stainless steel of the A5 type. It possesses the properties of the A4 type, but with increased temperature resistance. Furthermore, the A5 type 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.