Pipe threads are manufactured in many forms, but the most common types are straight and tapered threads. Straight pipe threads are gaged with the “GO” & “NO GO” process like regular threads, but tapered pipe threads require an entirely different gaging method: A series of one to three “L” checks. In this video, we’ll cover how to gage the three types of American tapered pipe threads: NPT which stands for National Pipe Taper, and NPTF which stands for National Pipe Taper Fuel and comes in Class 1, and Class 2 classifications.