The difference between system A and System B is as follows. System A is plus or minus a turn from notch location vs System B which uses the back face of the gage to check for maximum material.
These gages also come in truncated or full form. The difference being is the truncated crest will allow you to check the pitch diameter but not the radius. The full form allows you to check the radius of the thread.
This is easy. The Whitworth Screw Thread Form found in the various published standards for: BSP; BSPP; BSPT; BSW; BSF; G-series; R-series; all require a radius screw thread root and screw thread crest for both the internal screw thread and the external screw thread.
This is easy. The Whitworth Screw Thread Form found in the various published standards for: BSP; BSPP; BSPT; BSW; BSF; G-series; R-series; all require a radius screw thread root and screw thread crest for both the internal screw thread and the external screw thread.
WHAT IS TRUNCATED? Truncated is a very flexible word. The definitions range from very complicated to quite simple and its use covers a wide range of topics. Look it up on Google and see what I mean. In this situation I believe that the two definitions that make the most since are: 1) Geometrically speaking; truncation is an operation that cuts a shape creating a new facet. 2) The most basic definition; truncated means shortened. The Whitworth screw thread form is sometimes modified by cutting off the radius and replacing it with a flat, basically shortening the screw thread form.
Click below to download information on British Thread Gages
Full Form vs Truncated Threads
