Making A Threading Die.

[xrayjello]

Hello folks, I'm in the process of making a 1/4-40 thread die. I had some finished samples but they wouldn't cut. They were hardened to file hard. I'm wondering if there are some other things I could do. The are 1" diameter, 3/8 thick, 3 relief holes. I used a 82d counter sink and wonder if it was to much and perhaps to deep? They wouldn't even start a cut. Tried using more force, just tore the threads off the die about 1/8". Any help would be appreciated.

 

[Bob Korves]

Hi neighbor! Welcome to Hobby-Machinist!
Can you just single point the threads on a lathe? If not, those dies are quite available on the web, here is just the first hit of my search:
http://www.victornet.com/tools/Round-Threading-Dies/1861.html
Making a small die like that capable of producing accurate threads in commonly machined metals is no trivial task. I for sure would not even attempt it.
I looked and I do not have one on hand...

 

[Bob Korves]

If you want to persist at making your own die, make sure to temper the die after it is hardened or it will be brittle. Make sure that the cutting edges have a slight positive rake where they meet the work. Have the teeth of the die thick enough to support the cutting edge. Make sure the cutting edges are razor sharp. What material are you trying to make the die from?

 

[xrayjello]

At the time I was doing it because it was quicker than ordering, and unlikely to be in the local stores. I think the material was 4130. It was a learning lesson I thought I'd take advantage of. I will probably purchase one, but I would still like to make one. I was trying to cut drill rod. How do I make positive rake?

 

[Bob Korves]

(snip) How do I make positive rake?

https://en.wikipedia.org/wiki/Rake_angle

 

[xrayjello]

Thanks but that isn't clear to me in this application.

 

[pdentrem]

Look at the teeth on a regular tap. Ignore a thread forming/metal displacing taps, as they are different. The teeth have a positive rake and you need the same on a die.If you look closely at the first photo in the other thread, you see how the cutting teeth are intersecting the holes that I put in after cutting the thread cutting teeth. This builds in the angle required to make it work. I may not be explaining to well but I hope that picture helps you get there.
Pierre

 

[Bob Korves]

Thanks but that isn't clear to me in this application.

Contacting the work with a negative rake requires less power to push the cutter through the metal. I was going to find you a YouTube video on how to do it, but can't seem to find one with a quick search. Seriously, making a die is not a trivial pursuit, and that is why there aren't a hundred videos out there on how to do it... Which is not to say it cannot be done. I'm sure you can figure it out if you keep after it. Keep us updated with your efforts, it would be quite interesting to see it being done.

 

[Bob Korves]

Hello folks, I'm in the process of making a 1/4-40 thread die. I had some finished samples but they wouldn't cut. They were hardened to file hard. I'm wondering if there are some other things I could do. The are 1" diameter, 3/8 thick, 3 relief holes. I used a 82d counter sink and wonder if it was to much and perhaps to deep? They wouldn't even start a cut. Tried using more force, just tore the threads off the die about 1/8". Any help would be appreciated.

It occurred to me that I actually have a die that appears to be shop made. See the four pics. It is quite old, has no writing on it, and I cleaned the rust off of it some time ago. It is definitely 20 tpi, and the threads are very nice and actually have a nicely formed lead in, but it is between 5/8" and 3/4" bolt size, guessing somewhere around an 11/16" O.D. thread. It has a crooked hack saw slot cut across one side of the die for adjustment. I have absolutely no idea what it could have been made for. It came with a lot of old tools that I purchased a couple years ago. The die is hardened, appears to be carbon steel, and it has a small piece of metal jammed in the saw cut, trying to open it up a bit is my guess. If only old tools could talk!!! Note the positive rake...

 

[brino]

Also, 4130 probably isn't great for a cutting tool, you would want something with a higher carbon content that can be hardened (harder than what your cutting) but then tempered back to not be too brittle. Perhaps a tool steel.

An interesting endeavor, I have never made a die, but I have made a tap for plastic from a bolt.
Please post back with your progress!

-brino