Making A Threading Die.

One thing that makes shop-made dies difficult perhaps to the impractical point is the back relief. The cutting edge is really the only part of the thread profile that touches the part being threaded. Each short section of thread of the die is ground in such a way that there is some taper in it. If you have a simple round thread, with holes cut in it to form the edges, you won't have any relief and that part of the thread form in the die will only rub or drag on the thread as they are being cut. Not all of the die threads touch the workpiece. Just the cutting edges. That's one reason factory dies have a "start from this side" marking. They aren't designed and don't cut well or at all if you try to run them on backwards. They just rub.
 
Tony- interesting. I would have not guessed that.
Xrayjello- I assume you are single point internal threading the die?
Robert
 
How did you make it? I remember seeing step by step instructions in some old gunsmithing books. I guess to replace screws with uncommon thread sizes. I think you need to have a good amount of taper from the starting side and relieve the cutting edge carefully. I think it shouldn't be too hard to do using a dremel type tool with a grinding stone. I've never made one but I have cleaned up shoddy Chinese ones that way.
 
Thanks for all the replies. I used a tap to cut the threads. Had a old machining book using this as a example. That was the only steel I had to use, may try on brass or aluminum to see if it does better after I try to sharpen. I think that I've made life more challenging with the size of the relief holes, makes it difficult to sharpen. I think I understand more about the rake based on the above pictures. Will let you know once I'm able to sharpen or if I try to find some drill rod and start again. Thanks!
 
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