In an order of my regular client,he requested thread hole in the blind flanges.And the type of thread is WHITW.As follow:BLIND FLANGE/C PN16 WITH 1/2″WHITW.THREAD HOLE  H445/DIN2527   RST37-2.

So i searched some common thread types and made a simple classification.

NPT,PT,G are all pipe threads.

ASTM A182 F91 threaded elbows in Haihao Pipe Fitting Factory

1.NPT is the abbreviation of national (American) pipe thread,which is a 60-degree taper pipe thread of the US standard for use in North America.

2.PT is the abbreviation of pipe thread,which is a 55 degree sealed tapered pipe thread.It belongs to WHITW thread and is used in Europe and commonwealth countries.Commonly PT thread is applied to the pipe industry of water and gas,the taper is 1:16.

3.G is a kind of thread of 55 degree non-threaded sealed pipe,belonging to the WHITW thread.G stands for cylindrical thread.G is the general name of the pipe thread (Guan),the division of 55, 60 degrees is functional, commonly called the pipe circle.That is,the thread is machined from a cylindrical surface.