Size of third-hand holes

I’ve bought some of the flexible coolant pipes and want to make my own base but need to know what size hole and thread type to make the holes.

The product page for the flexible arms says “½”-20 pipe thread" so this would suggest a 1/2" hole but not sure what the “20 pipe thread” is referring to?

Also, is it NPT or BSP thread?


Hi Jeremy,


½" means a 1/2" nominal diameter, and the -20 means 20 threads per inch.

I believe they are actually a straight thread, if you have one already then you could determine the taper of the thread if any.

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