Monday, April 11, 2016

Threading Die for Bagpipe Mouth Piece

Building a 9/16" by 30 TPI threading die for a local bag pipe shop

Difficulty Level (Easy, Medium, Hard, Insane):

A local bag pipe shop owner called me a couple of days ago asking if I could make him a custom die so he can thread some stock delrin with a 9/16" by 30 TPI male thread. After some research I found that a 30 TPI is a virtually non-existent pitch so there was no dies available that I could find.

I did find a matching tap but it was over $80 bucks. When I planned out how to make this die I figured if I can thread a piece of O1 tool steel to the proper size, I could mill some relief angles to make the cutting edges, harden and sharpen it and then use this custom tap to cut the inside threads of a piece of 4140 steel. Once that was tapped I would heat, quench and temper the final die so that's what I set out to do.

Unfortunately, after several hours when I had finally completed the tap I used my belt sander to cut some relief angle into the tap just to realize when I was done that I had done so at the wrong side and essentially dulled the tap beyond any use.

After I got over the disappointment, I figured I could use the Threading Insert Tool Holder that I had used to make the Milling Head Ejector Nut and skip the tap altogether.

After cutting off a 1/2" piece of 4140 on my fixed Metal Band Saw, I chucked it up, faced both sides, drilled and bored it to size and then used my 39 Tooth Gear to enable my lathe to cut 30 TPI threads.

After the bored piece was tapered on one side to make it easier to start the tap I cut the internal threads which actually worked out quite well.

Once the threads were cut, I mounted my DIY Dividing Head, set my mill to the horizontal position and drilled 6 equally spaced relief holes.

All I had to do now was heat the die with my Propane Burner, quench and temper the die, then do a final sharpening of the cutting edges as well as some cosmetic clean up and engrave the size and TPI values on the die.

The bag pipe piece the final threaded piece should fit into
Another view of the piece with the female thread
A piece of delrin
The 1/2" piece of 4140 I cut up to make the die out of
A 3" piece of 3/4" O1 tool steel to make the tap out of
The chart showing how to enable a 30 TPI thread on my lathe
Facing the O1 tool steel
After the O1 tool steel was threaded and tapered
Setting up my dividing head
Cutting some relief into the tap
The finished cutting end of the tap
Turning the shank down to 1/2"
The finished tap
Another view
Heating the tap
The glowing red hot tap
Quenching the tap in some old motor oil
A layer of oil smoke in my shop. I thought it looked kind of cool
The hardened tap
Drilling the die blank
Mounting it on an arbor to turn the outside to a bit under 1"
Boring the die
Another view
Threading the inside of the die
Using the tap to clean up the inside thread
Another view
Drilling some recesses to hold the die in the die holder with the set screws
The die mounted in the die holder on the tap in the vise
Another view
After the relief holes were cut; I did not have enough material along the insides and the cutting edges were too wide
Another view of the (first version) finished die
Another view
Turning the delrin to 9/16"
The new (first version) die in the holder
Close-up of the delrin turned to 9/16"
The inferior threads left with the first version die
Threading the second version die blank
The threaded die
Fitting a test piece on the die
Getting ready to drill the relief holes
Closeup of the setup
Testing how 8 relief holes would work out. I ended up deciding against it
Six relief holes looked better so I went with that
Cutting the first relief hole
After all the holes were cut
The finished, non-hardened (second version) die
Getting ready to heat the die
The glowing die just before quenching it
The hardened die
After I cleaned it up on the belt sander
Engraving the die size with a diamond tipped dremel bit
The completed 9/16" - 30 TPI die

Lathe and accessories
Threading Insert Tool Holder
Metal Band Saw
39 Tooth Gear
DIY Dividing Head
Propane Burner
Belt sander
Tap & die set

3" of 3/4" O1 tool steel
Two 1/2" pieces of 1-1/4" metal (4140)


7 hrs


It works and looks really nice. I'm amazed how many uses for my lathe I have discovered since I got it last summer.


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