Tapping Pipe Fittings

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

Tapping Pipe Fittings

Postby Soot n' Cinders » Mon Nov 13, 2017 6:21 pm

I just received my first handful of MTP pipe fittings for my shay from Eccentric Engineer. They're really nice looking fittings! But I cant seem to get a grip on them to tap them. The first ones Im trying to tap at 1/4" 45 degree regular elbows. I tried holding the elbow in a small smooth drill vice with marginal success but Im afraid putting much torque on that setup with bend the casting slightly out of round, not a big deal for no pressure oil lines but definitely a problem for pressure lines.
So my question is how do you hold these little fittings to tap them? I also purchased a handful of street elbows to play with so I will need a setup to hold them steady while I run a die over the male ends. Thoughts?
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

KarlKobel
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Joined: Sun Mar 31, 2013 9:53 pm

Re: Tapping Pipe Fittings

Postby KarlKobel » Mon Nov 13, 2017 6:39 pm

I made some split - round holders, held together with two SHCS.

I'll take some pictures of them and post them.

Karl

BClemens
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Joined: Sat Oct 08, 2016 10:04 pm

Re: Tapping Pipe Fittings

Postby BClemens » Mon Nov 13, 2017 6:50 pm

Tristan,
You'll need to make a 'pocket' holder of aluminum (or even hard wood) with an appropriate sized ball end mill to make a mold type two piece clamping device - like a mold to fit and clamp the fittings solid. (It's like doing more work on the fixture than doing the whole job.)

The valve castings definitely need a fixture like this. That's the only 'safe' way to tap the 45° elbow since as you have found; there is no way to hold them from rotating without damaging them - the street ell too. There's a series on the forum about this....memory fails who did it.

Found it: machining+valve+bodies#p333252 He's a Bill C too - but not a Clemens though.
BC

Karl beat me to it!

Bill C
Posts: 216
Joined: Fri Aug 08, 2008 9:14 pm
Location: Pensacola, FL

Re: Tapping Pipe Fittings

Postby Bill C » Mon Nov 13, 2017 8:49 pm

Here's a link to the 2 minute video I posted showing the finished jig for the globe valve:

http://youtu.be/63FNuddqkzM

I got the idea from some photos and posts on a separate discussion board (either Home Model Engine Machinist or Hobby Machinist). I found those posts by simple google searches for PM Research fittings.

Hope that helps!

Bill "the other" C.

Bill C
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Location: Pensacola, FL

Re: Tapping Pipe Fittings

Postby Bill C » Tue Nov 14, 2017 1:03 am

Here a photos I saved from the other thread referenced above. Like I said, credit goes to others for the idea and these jigs.

Bill C.
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DianneB
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Joined: Tue Aug 21, 2012 3:05 pm
Location: Manitoba, Canada

Re: Tapping Pipe Fittings

Postby DianneB » Tue Nov 14, 2017 6:33 am

I just did a set of PM fittings last month - my FIST time ever doing fine machine work! I used Tubalcain's video as a guide https://youtu.be/2E-cqeWWsTU

I screwed up a couple of pieces learning but most came out okay. I had fairly good luck using the milling machine vice and a piece of threaded rod as a guide for the fitting angle.

The one thing I learned to machine a good fitting is to do all operations for each end of the fitting in a single clamp - i.e. machine the end flat, centre drill, tap drill to depth, then tap. It means a lot of tool changes but it works. The 45 degree elbows are the most challenging!

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Carrdo
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Location: Toronto, Canada

Re: Tapping Pipe Fittings

Postby Carrdo » Tue Nov 14, 2017 4:36 pm

The MayJune 2004 issue of Live Steam deals with this also in an article entitled "Machine Your Own Model Pipe Fittings" by Paul J. Smeltzer.

KarlKobel
Posts: 83
Joined: Sun Mar 31, 2013 9:53 pm

Re: Tapping Pipe Fittings

Postby KarlKobel » Tue Nov 14, 2017 10:06 pm

Mine look like Bills - nice job.

Karl

jscarmozza
Posts: 205
Joined: Mon Mar 03, 2014 5:09 pm

Re: Tapping Pipe Fittings

Postby jscarmozza » Wed Nov 22, 2017 9:08 am

The discussion motivated me to start on some of my fitting castings, I mulled the different techniques and like Mr. Pete started with the simplest fitting, the coupling. I ran my MPT tap into the coupling 4 complete turns after it took a bite, then to see how it would make up with a pipe, I threaded the end of a 1/4" piece of copper tubing (6threads). To my surprise, when I tried to turn the pipe out of the fitting, it tore along the helix of the thread and came out like a cork screw! Any thoughts on what happened? John

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Fred_V
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Re: Tapping Pipe Fittings

Postby Fred_V » Wed Nov 22, 2017 9:23 am

Your copper tube is thin walled from Home Depot or... You need thick wall copper from a refrigeration supply house if you plan to thread it.
Fred v
Fred V
Pensacola, Fl.

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Builder01
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Location: Erie, PA

Re: Tapping Pipe Fittings

Postby Builder01 » Wed Nov 22, 2017 9:42 am

If these are the taps and dies from PM research, they work best with heavy wall brass tubing. The taps and dies works great with the brass tube they sell. It is heavy wall, unlike the K & S tubing.

David

jscarmozza
Posts: 205
Joined: Mon Mar 03, 2014 5:09 pm

Re: Tapping Pipe Fittings

Postby jscarmozza » Wed Nov 22, 2017 10:21 am

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


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