Hex nut, according to the nominal thickness, is divided into type I, type II and thin nut. Hex Jam Nut. Above Grade 8 nuts , which is divided into Type 1 and Type II two types.

I type hexagon nuts widest application, a nut is divided into A, B, C three, where A and B grade nuts applied to the surface roughness is small, the high requirements for precision machinery, equipment and structures, and C grade nuts are used for relatively rough surface of the machinery, equipment or structures less precision; type 2 hex nut relatively thick, more often need to be used in assembly and disassembly of the occasion.

Type 1 nut refers nominal nut height m≥0.8D ordinary hex nut, of the type size should be consistent with the provisions of GB / T6170's;

The height of type 2 than type 1 nut to nut, of the type size should be consistent with GB / T6175. Increase in type 2 nuts two purposes: First, to obtain a nut without heat treatment by increasing the height, relatively low nut.

The hex jam nuts are cutted from common hex nuts. Cost is higher.