G TAPS BSPF BRITISH STANDARD PIPE PARALLEL

Sutton Tools manufactures a comprehensive range of G (BSPF - British Standard Pipe Parallel) thread taps designed for both light trade maintenance and high-performance industrial production. These 55° parallel pipe thread taps are widely used for gas, plumbing, and fluid-power fittings. BREAKDOWN OF 1/8 X 28 1. The "1/8" Nominal Size In pipe threading, 1/8 inch does not measure the physical outside diameter of the metal thread. It historically refers to the approximate inside diameter (ID) of the steel pipe. The actual physical outside diameter (OD) of a 1/8 BSPF thread is much larger, measuring 0.383 inches 9.73mm. 2. The "28" Pitch This number defines the thread density. There are exactly 28 crests per axial inch of thread length. To find the distance from one thread point to the next (the pitch), you divide 1 inch by 28. Pitch= 1 inch Divided by 28 = 0.0357 inches 0.907mm 3. The "BSPF" Profile Parallel Threads: Unlike BSPT (tapered) threads which seal by binding together, BSPF threads maintain a constant diameter along their entire length. They require a sealing washer, gasket, or O-ring at the base of the joint to prevent leaks. 55° Whitworth Form: The thread profile features a \(55^{\circ }\) V-shape angle with rounded crests (tops) and roots (bottoms), unique to British standards 1. Taper Tap (The Starter) Design: Features a long, gradual chamfer at the tip covering the first 7 to 10 threads. Purpose: Used to start the threading process. The long taper allows the tool to easily enter the drilled hole, align straight, and gently begin cutting the first shallow groove. Limitation: It cannot cut a complete thread to the bottom of a hole because the tip is narrow and lacks full-sized cutting teeth. 2. Intermediate / Plug Tap (The Follower) Design: Features a shorter chamfer at the tip covering the first 3 to 5 threads. Purpose: Used after the Taper tap to cut the threads deeper and closer to full size. In a "through-hole" (a hole drilled all the way through the metal), an Intermediate tap is often the final tap needed to finish the job. Note on Terminology: In the UK, Australia, and BSW standards, this is widely called an Intermediate tap. In the US, it is commonly referred to as a Plug tap. 3. Bottoming Tap (The Finisher) Design: Features a very short chamfer at the tip covering only 1 to 2 threads. The rest of the tap features full-sized, sharp cutting teeth. Purpose: Used exclusively to finish "blind holes" (holes that stop mid-way through the metal and do not go all the way through). It allows you to cut full, usable threads right down to the very bottom floor of the hole. Limitation: Never use this tap to start a hole. Because it has no guiding taper, it will wobble, cross-thread, or immediately snap under the sudden cutting pressure.