Button die question...

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Ca-g

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I have a smalal button die which works perfectly until I back it off at which point it destroys the thread. I have looked closely at the cutting edges and it looks OK, but something is wrong. Is this a common thing with a typical cause..?
 
What's the thread size and pitch and your workpiece diameter?

My first thought without the above information is that you're running the die on a diameter that is too high resulting in very sharp threads. When you back the die off, it's easy to cross thread resulting in buggered threads.

I usually undersize the diameter of the workpiece by 2-4% depending upon material and thread size/pitch

Phil
 
Phil,

Thanks for the thought. It is a M2.5 die and the material is steel, and it is true I was trying to make the thread as close to 2.5 as possible in the hope of making a stronger thread. I think imperial in small sizes, so the turned size was 98 thou.

I will try it again with about 95thou and see what happens.
 
More thanks Phil, relaxing on the major diameter left me a decent thread...
 
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