Distinct Thread Standards in Uses

1. GB, six forms of the A B C D F H are inclued in the GB,

Type A is the flat O-ring seal metric thread

Type B is for the national standard bite-type metric thread, used for the metric thread bite type tube fitting

Type C is the national standard 74°cone type

Type D is spherical type

Type F is flange seal, in line with SAE standards

Type H is 24°cone O'ring seal, but several specifications are different to those of German standard

2. German standard, it largly uses metric 24°cone O'ring seal, the flange seal standard is as same as the standards of GB.

3. American standard, it has JIC standard and ORFS standard, JIC is the US thread, and those threads are usually fine threads, such as the SAE Adapter JIC 37°. 74° cone, ORFS are the US thread as well, they are flat seal but the seal groove is quite different to those of the national standard.

4. Japanese standard, it is JIS standard, BSP/BSPT thread, 60° cone.