[Newbie] What thread size is this?

[Macmandr197]

Depends on the quality or the tap. Some inexpensive taps aren't sharp. With plastics I find a a sharp tap works better to cut the threads cleanly rather than a duller tap that kinds of cuts & forms the threads. Worth a try & you might be ok. Since it's NPT and it's tapered you can tap deeper if the fit is too tight. Keep in mind with a tapered pipe thread tap you don't want to tap all the way to the end of the tap.

Okay, so with this I just tap until the tap comes through the other side? The established threads that is, not just the edge of the tap

 

[darkzero]

Okay, so with this I just tap until the tap comes through the other side? The established threads that is, not just the edge of the tap

I would tap like halfway on the tap then test fit the male fitting. Then tap deeper if needed. I don't have a whole lot of NPT taps but with mine I find I only need to tap like 3/4 of the way but that's usually in metal.

 

[Macmandr197]

Awesome, thanks

 

[kd4gij]

3/4 is standard 3/4 of the tap thread that is

 

[Macmandr197]

3/4 is standerd

?

 

[gwade]

Most need tapped so the threaded pipe (or adapter) in this case is about 6 threads of engagement.

 

[benmychree]

The general rule with a pipe tap is to allow 5 threads still showing on the shank end.

 

[P. Waller]

Your customer is not likely to screw a plug gauge into the hole then reject the parts as being non-compliant (-:
Tap it until the fitting screws in close to the hand tight thread engagement dimension listed here, you will be more then close enough for plastic fittings.
https://www.engineersedge.com/hardware/taper-pipe-threads.htm

Or buy a plug gauge if you are terribly worried about the fit.
https://www.mscdirect.com/browse/tn/?searchterm=3/8+npt+plug+gauge&hdrsrh=true

 

[whitmore]

Could anyone help me with identifying the tap size and drill size for this thread?

While it's very likely 3/8 NPT, it could also be 3/8 NPS; both are the same pitch, 18 tpi, but for attaching with a nut,
the NPS isn't tapered (conical), but straight (cylindrical). An NPT die can convert it from an NPS, and I've had to do that
once or twice.

 

[Tozguy]

I'm just tapping plasting,

How thick is the plastic?
Why not just make your own tap. Buy a cast iron fitting with the same thread (3/8 MIP, NPT or whatever) and cut slots in it.
It will cut any plastic no problem.