Tips for machining small pipe fittings

[Generatorgus]

When I built my half scale H Ford engine I had a heck of a time trying to indicate and hold the 1/8 NPT fittings I used for the valves, and ended up using the square machined type fittings.
This time around, I'm going for a 1/3 scale using the 1/4" MTP cast fittings from PM Research, for a more authentic look
I've already started the build and have the casting tree and tap and die on hand.
Before I jump in and start messing them up I'd appreciate some input from someone with experience at it.
As to machining the threads, I don't feel I'm up to it, just yet anyway.

GUS

 

[ShopShoe]

Generatorgus,

See this thread by Metal Butcher:

http://www.homemodelenginemachinist.com/f25/tapping-model-pipe-elbows-12911/


Followed up a few days later by this from Brian Rupnow:

http://www.homemodelenginemachinist.com/f25/drill-jig-45-degree-elbows-17244/

Good luck and show us your result.

--ShopShoe

 

[Generatorgus]

ShopShoe, Thanks.
That's the kind of reply I was looking for.
For some reason my searches don't give me the results I want.
I'm not quite ready to start into the fittings but it should be fairly soon.
GUS

 

[Generatorgus]

OK, I'm making progress, but now I can't find any thing that tells me the tap drill for 1/40 MPT thread, as well as how many turns/threads.

As usually
Puzzled in PA
GUS

 

[Tin Falcon]

http://www.guhring.com/documents/Tech/Formulas/Tap.pdf

Print this out and put on the wall or in the machining notebook.


Tin

 

[idahoan]

Hey Gus

For a 1/4-40 MTP you would use a #5 drill; as far as number of turns I would just give it a few turns and test it with another fitting, then sneak up on it.


From my Bay-COM chart; all MTP threads.
1/8-56 #40 Drill
5/32-48 #30 Drill
3/16-40 # 23 Drill
1/4-40 #5 Drill
5/16-27 Letter F Drill

Dave

 

[Generatorgus]

Thanks guys.

I tried searching the internet, but kept coming up with NPT stuff, and also found one saying it was the abbreviation for Male Pipe Thread.
Seems that my latent dyslexia allowed me to type MTP rather than MPT.(did it again:wall just turn them around.
Just tried MTP and instantly found these:

http://livesteamsupplies.com/livesteamsupplies_015.htm
http://www.americanmodeleng.com/id54.html

Live steam chart won't print, but Amer.Model does.

GUS

 

[Tin Falcon]

Amazing what you can find with Google when you type the correct search sting
Tin

 

[Generatorgus]

Ok, after I got the two alum blocks cut a little oversize, I rough figured where the pin locations would go I drilled and reamed them, loctited the pins to one side and milled the combination down to make a nice square block, as per the sketch metal butcher posted in his build.
http://www.homemodelenginemachinist.com/f25/tapping-model-pipe-elbows-12911/

When I laid out the pins I thought I left enough room for the fitting bores, but, unfortunately, I was wrong and the top hole was going to interfere with the 5/16" hole, so I put it aside and started over. I think that this block might be OK for a 3/16" fitting.
New block made I drilled the 5/16 cross holes and made the two shallowest counter bores and tried the casting. Not a bad fit with a little tweaking. I also noticed that it looked like the bottom c'bore would bump the edge of the top pin.



I would have to pull the pin, plug the hole and move it over a little. But I went ahead and drilled and tapped an el fitting which came out good.

.




I didn't have any 1/8" alum rod on hand so I made a piece from 1/4 round.
Not wanting to lose alignment of the halves I figured I could Loctite the plug in thru both halves, drill the new hole, punch out the other pin and the drilled plug would snap in half with a little twist and it would be a simple task to reinstall the pins. Not so, one half of the plug broke out of it's bond.



Ok, just cut the piece off and re-glue it along side of the pin. I cut it and it dropped and disappeared somewhere on the floor I just swept the day before. Luckily the new hole was far enough away that I should be able to do without the filler. I finished the counter bores and again with some tweaking I tried a tee and it was happy, happy, happy.








I didn't drill and tap the tee yet, because, hopefully, it is going to become the intake valve housing for the new 1/3 scale H Ford I'm currently building, which I'm going to rename the Lil' Henry, and I've decided to go ahead post the build.

Not sure at all if this engine will run, some of it is still on the drawing board, it will indeed make a nice shelf pet if things don't work out.

GUS

As a little teaser, you can see part of the Lil' Henry's base in the first pic of this post.

 

[ShopShoe]

Looks like you're off to a good start.

I'll look for Li'l Henry.

--ShopShoe