Deeper threading

[Laurenr]

When I am tapping threads, I'm not getting the depth and sharpness with the die like I'm getting from the tap. Inner threads are very crisp and deep. Outer threads are fuzzy and ill-defined.

Ideas?

 

[mredburn]

Could be a few things, poor or dull die, material is not holding together at the end of the threads since its being sheared with nothing to help hold together. The tenon your cutting may be to small although you should have sharp threads right up to the ends even if your not getting a point on them. The tenon could be to large and its breaking off as it goes through the die ruiining the threads. Does it do the same thing on different materials?

 

[Laurenr]

The dies are new. I'm thinking maybe the tenon is too large. I have been erring in the side of bigger to solve the problem, (that would be my MO generally). If I am cutting 9x.75, and cut a 9.25mm tenon, is that too much?

 

[Hendu3270]

I believe if your tenon is slightly larger than needed (within reason, not too much bigger), your threads should be better than if your tenon is slightly undersized. I know if my tenon is too small the threads are flat on top and if the tenon is too large, I'll hear some odd sounds (crunching) as the die struggles to remove the larger amount of material I'm trying to make it cut. If this happens the threads look very bad.

I'm pretty new to componentless pens so I don't have as much experience as some of these guys.

 

[Laurenr]

I think that was it. I just cut three different tenons, and the sharpest threads were on the tenon that measured 8.75mm. Who'da thunk?

 

[Rich L]

That's the way it's supposed to be. Basic major diameter on external threads is less than the diameter indicated by the basic thread designation ( e.g. "9" x .75 ). Your tenon should be cut so that you're not trying to cut the very crest of the thread. The crest should be flat - roughly 1/8 of the thread height in width. With an excess in diameter you're just cramming excess material into the die and it is not cutting that material - it's tearing at it.

Cheers,
Rich

 

[mredburn]

Normally I will cut a tenon .2mm smaller than the die is rated for. Or 8.8mm and adjust up or down if I need to. I would drill a hole 9.3 to 9.4 for the tap.

 

[Laurenr]

You guys are golden! Thanks.

 

[Ed McDonnell]

Normally I will cut a tenon .2mm smaller than the die is rated for. Or 8.8mm and adjust up or down if I need to. I would drill a hole 9.3 to 9.4 for the tap.

A 9.3 to 9.4 hole would be super easy to tap with a M9 x 0.75 tap.....You wouldn't even need to turn anything. Just push the tap into the hole. :biggrin: You might get better threads with something like a 8.3 to 8.4 hole :wink:.

Ed

 

[mredburn]

lol didnt even catch that.