Tools & Gear Taps & Dies Chrome Alloy Taps

4252-1/2B 1/2 NPT Chrome Alloy Tap - Bottoming Chrome Alloy NPT Bottoming Hand Tap. Used as thread chasers to clean an existing thread. They can also be used to create a new female thread in non-ferrous metals and plastics. Chrome alloy taps are not suitable for creating precision, safety or critical threads. National Pipe Tapered is a US standard for tapered threads used to join pipes and fittings. ANSI/ASME standard B1.20.1 covers threads of 60° form with flat crests and roots. The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other. However a clearance remains between the crests and roots of the threads, resulting in a leakage around this spiral. This means that NPT fittings must be made leak free with the aid of thread seal tape or a thread sealant compound. For each 12" increase in distance from the end, the diameter increases by 3/4". Bottoming Taps have a lead of two threads and are used to ensure minimum thread run-out when tapping to the bottom of a blind hole.