Tapping Pipe Fittings

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Soot n' Cinders
Posts: 623
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
Posts: 83
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
Posts: 252
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: 214
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
Posts: 214
Joined: Fri Aug 08, 2008 9:14 pm
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
Posts: 488
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
Posts: 921
Joined: Thu Mar 06, 2003 2:20 pm
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


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