NPT TAPS SUTTON

Sutton Tools offers a comprehensive range of National Pipe Taper (NPT) taps tailored for creating airtight seals in pipe fittings, available in both budget-friendly carbon steel for maintenance and high-speed steel (HSS) for industrial workshop applications.

• NPT: Refers to National Pipe Taper, the standard American pipe thread profile. It features a 1:16 taper (0.75 inches of diameter change per foot of length) which ensures that as a fitting is screwed in, the threads jam together to create a fluid-tight joint.
• 1/8: This is the nominal pipe size, not the physical dimension of the tool. The actual outer diameter at the gauge line of a 1/8'' NPT tap is 0.405 inches (10.29 mm).
• 27: Represents the thread pitch, which is 27 Threads Per Inch (TPI). Each individual thread profile sits exactly 1/27 inch (≈ 0.94 mm) apart from the next.
• Bottoming: This identifies the chamfer geometry at the tip. While a standard NPT tap has a long, gradual entry taper spanning 3 to 5 threads, a bottoming tap has a very blunt tip with a chamfer of only 1 to 1.5 flat, truncated threads. This geometry allows it to cut fully formed threads almost completely to the floor of a shallow hole.

• The NPT Depth Trap: Because NPT relies on a taper to seal, an NPT fitting must screw in to a specific depth to reach its tight, interference fit. If your blind hole is too shallow, a standard tap cannot go deep enough to widen the opening to the correct size. The bottoming tap solves this by positioning the required sealing diameter much closer to the tip of the tool.
• Two-Step Threading Process: You cannot start threading a blank, smooth hole with a bottoming tap. Because it has almost no entry chamfer, it will fail to align, skid across the surface, or instantly bind and snap. You must first cut the thread as deeply as possible using a standard Taper or Plug NPT tap, clear out the metal chips, and then use the Bottoming tap to extend those threads to the floor.
• Pre-Drill and Ream Sizes: For optimal results, drill the initial hole with a Q size drill bit (0.332 inches / 8.43 mm). Because NPT threads are tapered, it is highly recommended to follow the drill with a specialized 1:16 taper pipe reamer before tapping. Reaming removes the excess material at the top of the hole, drastically lowering the torque required by the tap and preventing tool breakage