Here's a question for any machinists or plumbers out there. I have an 1/2" pipe clamp from HFT. I need to thread the pipe to fit the clamp. I thought an 1/2" -13 die would do it. Wrong! The question, what size die do I need to thread the 1/2" pipe to fit the clamp thread of the 1/2" clamp?

1/2" pipe die. You see the pipe threads are tapered, the 1/2" comes from the internal diameter of the pipe.
Since the threads are tapered you will need to check the fit of the clamp to the threaded portion of the pipe.
Or hit Home Depot or such & buy a piece of threaded pipe, probably cheaper than the die.

... short for national pipe thread. So 1/2" NPT oughta do ya.

( which is too small ) is different from an 1/2" NPT?

Yes, you have a bolt thread die, you need a 1/2 NPT--national pipe thread.Than there is tappered and straight thread, tappered is used for air, water pipes etc. Straight thread is usually used on ridgid conduit fittings because they don't need to seal.Hope this helps.Joe

Shootem all like you mean it.

they are tapered threads that need to be made up tight for sealing and grounding continuity.

As an Electrician both features are important with threading.

Walter....

there is also a 1/2"-20 which is the national fine thread. On the other hand, the 1/2" pipe size is .840 nominal in diameter and the 1/2" NPT is a tapered National Pipe Thread designation. There is also a STRAIGHT 1/2" pipe thread that's .840 in diameter with 14 threads per inch.

The NPT tapered threads are for sealing liquids and the tapered joint gets tighter with tightening. Usually there is also some type of thread sealer used to make the joint leak proof.