12 Piece Carbon Steel NPT Pipe Tap and Die Set, 1/8", 1/4", 3/8", 1/2", 3/4" and 1" in Wooden Case. Drill America Carbon steel pipe taps are designed to clean and or re-thread damaged or jam pipe threads Also called 'pipe taps', National pipe taper taps are appropriate for Threading a wide variety of materials both ferrous and non-ferrous. The nominal size of a pipe Tap is that of the pipe fitting to be tapped, not the actual size of the Tap. The thread tapers 3/4 of an inch per foot. All pipe taps furnished with a 2-1/2 to 3-1/2 thread chamfer. Not threads require the use of a “sealer” like Teflon tape or pipe compound. Carbon Steel Hex Dies are for dressing over bruised or rusty threads. These dies are the most cost effective re-threading tool available. They are ideal for maintenance in the shop or field.