09-12-2021, 09:37 PM
The topic of pipe threads is very confusing and although the situation can be fathomed by pondering the data it is seldom explained directly. 1/2 inch is based on the outside diameter of a nominal 1/2 inch bore thick walled wrought iron pipe as in use from sometime well back in the 19th Century. So the size is much larger than the name. The taper threads theoretically provided a watertight joint when forced together, although hemp or somesuch is usually necessary. Some medium point of the taper is adopted for the parallel version, used where adjustment is necessary and for railings etc. a parallel thread of sorts can be produced by mal adjusting two piece taper die sets.
just to be awkward the American system is not based on the 55 deg Whitworth thread and differs in dimensios, some pitches etc. Machinerys Handbook defines a myriad variants of the basic spec.
To add to the confusion, here the traditional and still standard BSP threads have been allotted nominal metric sizes! So oldies like me get funny looks when we ask for some 1/2 inch BSP fitting.
Incidentally I recall some Seven blocks have plugs for the gallery below the ports. Are these 1/2 BSP or smaller?
just to be awkward the American system is not based on the 55 deg Whitworth thread and differs in dimensios, some pitches etc. Machinerys Handbook defines a myriad variants of the basic spec.
To add to the confusion, here the traditional and still standard BSP threads have been allotted nominal metric sizes! So oldies like me get funny looks when we ask for some 1/2 inch BSP fitting.
Incidentally I recall some Seven blocks have plugs for the gallery below the ports. Are these 1/2 BSP or smaller?