Technical Pipe Thread ?

I would like to cut possibly 3/8” off 1/2” male pipe fitting so it fits neater as manifold plug.

Is taper on male or female side or both ? If taper is on male or both,
cam I assume my plan won’t work ?

 

Taper is on both.

 

Can you use allen head plugs for what you are doing?

Charlie Stephens

 

Both male and female are tapered pipe threads. Otherwise it wouldn't seal.
That's why there are tapered pipe thread dies and tapered pipe thread taps.
If you cut the male plug shorter you will have to rethread it.
Make sure you have enough metal left on the diameter to obtain a tapered thread
that will fit the female threaded hole with enough thread on the rethreaded male plug in to produce a seal.
If you "over thread" the male plug you will have no taper, hence no seal.

 

Of course !

Thanks

 

Latter part of question. No

 

The amount of threads on the taper determines the depth of the fitting. That is why you have a spec as to how far to run the tap or die. That is why you see some pipe threaded fittings “ ride high” and others almost bottom out . Both will seal if they tighten up. But to answer your question , use a pipe tap on the female thread and tap a little “ deeper” then take a die and thread a little farther on the male fitting. Your fittings will set “ lower” together! But be careful it you tap/ cut threads too much , it will not seal!






Bones

 

Thanks All. !

 

Can only tap deeper if you have enough material, or as mentioned run a risk.
I’d do the Allen head fitting, looks cleaner for sure.

 

Retired as a machinist after 30 years of making industrial parts, many times with internal/external threads, hated putting my name on them sometimes even though they were to spec. When making parts with tapered pipe threads for myself the aesthetics play a big part, meaning to not have a lot of extra thread showing (especially ugly when wrapped in teflon tape) so many times I have been known to tap a hole deeper to "sink" the male thread further into the part.
By the way, in general, hex driven pipe plugs do look much better.

 

To get the full 'sealing' you're supposed to have five full threads engaged. And like several have mentioned, be very careful about tapping the hole deeper, it's very easy to go too much. Sneaking up on it is the best way.

I'll also note that if threading into aluminum, it has more 'give' than iron or steel so go slow. Be sure to use some thread sealer or anti-seize, that can save the threads if removing the fitting later. And don't overtighten to try to get that 'last bit' as you can split the hole open.

 

I was taught, and it seems to hold true, that when tapping a female pipe thread, the tap should show 4 threads out of the tapped surface when at a “standard” depth/fit.

 

That number is purely dependant on the guy that makes the parts and the mfg's level of quality control.

 

Or use a nice brass fitting. Looks better than a steel one.

 

This problem was resolved before post #8, no further input is needed. Thanks.

 

The OP may have solved his problem, but for anyone else facing a similar dilemma, socket (Allen) plugs come in two versions: standard and 'flush'. A flush plug is designed to use the same thread depth, but has a shorter body height.

 

Thanks !

Didn’t know this. Ordered 2 off eBay,
have no idea which I’m getting.

 

Conduit threads are same pitch as NPT but no taper . As best as I recall . Tap and retread to these threads , seal with lock tite , and let it eat

 

Conduit threads are exactly the same thread as NPT, but the female fittings may or may not have the taper depending on type.

 

Stop it!