Tapping Pipe Fittings

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Soot n' Cinders
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Re: Tapping Pipe Fittings

Postby Soot n' Cinders » Wed Nov 22, 2017 10:26 am

jscarmozza wrote:Kinda figured that the pipe wall was too thin, Fred this was refrigeration tubing, I guess that's out for threaded piping material.
Do you know the proper number of internal and external MPT threads to cut into pipe and fittings, so they make up properly?
John


You want hard copper for threading as well. As far as number of threads, Ive found its just trial and error. Run the die over the pipe till the end of the pipe is flush with the back of the die. Then start with the tap and play with the depth till you get a fit you like. I have American Model Engineering Supply taps and dies and have found I need to leave about 2 threads of the tap sticking out of the hole.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

jscarmozza
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Re: Tapping Pipe Fittings

Postby jscarmozza » Wed Nov 22, 2017 6:22 pm

Thanks for the tips, my taps and dies came from PM Research, so a little experimentation is required in order to get the proper fit. Thanks again, John

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10KPete
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Re: Tapping Pipe Fittings

Postby 10KPete » Wed Nov 22, 2017 7:07 pm

jscarmozza wrote:Thanks for the tips, my taps and dies came from PM Research, so a little experimentation is required in order to get the proper fit. Thanks again, John


John, do you like the PM taps and dies? Are they sharp, etc. ?

I need to get a couple of sizes and don't want to QC all the offerings out there!!

Thanks,
Pete
Just tryin'

jscarmozza
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Re: Tapping Pipe Fittings

Postby jscarmozza » Wed Nov 22, 2017 7:42 pm

Hi Pete, P M Research was a pleasure to deal with and their products appear to be first class. The taps and dies are sharp and produce a clean thread, excellent on brass and very good on copper.

Happy Thanksgiving, John

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Bill Shields
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Re: Tapping Pipe Fittings

Postby Bill Shields » Wed Nov 22, 2017 9:28 pm

As a general rule, when working with any taper pipe thread die - you work to flush and call it quits...no point in going any further.

as already described, run the tap in, then perhaps wrap it with some tape for a reference for the next time when you don't remember

the bad thing about all of this is you generally need two taps....one to get started and one, with the end ground off, so that you can work blind holes - or 90 or 45 ells.

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10KPete
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Re: Tapping Pipe Fittings

Postby 10KPete » Wed Nov 22, 2017 10:05 pm

jscarmozza wrote:Hi Pete, P M Research was a pleasure to deal with and their products appear to be first class. The taps and dies are sharp and produce a clean thread, excellent on brass and very good on copper.

Happy Thanksgiving, John


And you as well!! Thanks for the review.

Pete
Just tryin'

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10KPete
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Location: Nordland, WA, USA

Re: Tapping Pipe Fittings

Postby 10KPete » Wed Nov 22, 2017 10:07 pm

Bill Shields wrote:the bad thing about all of this is you generally need two taps....one to get started and one, with the end ground off, so that you can work blind holes - or 90 or 45 ells.


Same in full size work... which means buying two of everything eventually. Not a big deal 'cause they'll out last me...

Pete
Just tryin'

jscarmozza
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Re: Tapping Pipe Fittings

Postby jscarmozza » Fri Nov 24, 2017 9:19 am

This turned out to be a timely discussion for me as I begin to overhaul and retrofit my engine over winter. I found most of the existing fittings and pipes on my engine to be threaded 1/4" x 32 TPI, and I'm wondering if I should redo everything in MPT or UST. After everyone went home yesterday I relaxed and read through the P M Research catalog that came with my order, lots of good information. One thing I discovered is that MPT threads have a smaller root diameter then UST or straight threads, that may be why my external pipe threads nearly cut through the pipe wall, coupled with threading the tubing too long. According to PMR an MPT tap will cut their proprietary UST if turned in 3 turns deeper. Since I have a 1/4"x40 MPT tap and die set, I think I'm going to get a 1/4" UST die and see if that produces stronger threads on copper tubing. I'll go with hard tubing where I can, but there are a few places where I'm going to have to use bendable. Good discussion, thanks for the input. John

Soot n' Cinders
Posts: 627
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Tapping Pipe Fittings

Postby Soot n' Cinders » Fri Nov 24, 2017 2:12 pm

Thanks for all the info guys! I tried a wooden jig with limited success. Will make a metal one from some scrap aluminum flat bar I’ve got when I get home from thanksgiving
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay


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