Threadforming Stressproof

Cole2534 · Feb 2, 2021

I have a tendency to break spiral flute taps in stressproof, always on retract in the lathe. I think the material's chip nature is the cause.

Regardless, I gotta do it. So how well do form taps do in this material? The threads are solely for fixturing so no crazy specs other than don't break off the tap.

Tips, tricks?

Edited for clarity.

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deltap · Feb 2, 2021

Use a gun tap. Drill a larger hole for 50% threads. Use sharp tap. Use dark thread cutting oil. If tapping deep clear chips half way.

sirAIG · Feb 2, 2021

Cole2534 said:
I have a tendency to break cut taps in stressproof, always on retract in the lathe. I think the material's chip nature is the cause.

Regardless, I gotta do it. So how well do form taps do in this material? The threads are solely for fixturing so no crazy specs other than don't break off the tap.

Tips, tricks?

Sent via CNC 88HS

I have no experience with this material, but when I am having issues tapping lower quantity stuff, I just opt to use a thread mill. If you have the ability (y axis), it may save you a bunch of headaches.

Matt_Maguire · Feb 2, 2021

Stressproof doesn't like to be cold worked.

Good luck,
Matt

atex57 · Feb 2, 2021

I used to do a pile of 1/4-20 and 5/8-11 in stressproof. I used a dab of Moly-Dee in each hole, 1/4 at 500 RPM and 5/8 at 200 worked fine. A fast reverse seems to help.

Ed.

Cole2534 · Feb 2, 2021

Matt_Maguire said:
Stressproof doesn't like to be cold worked.

Good luck,
Matt

That's exactly what I was anticipating.

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Mtndew · Feb 3, 2021

Cole2534 said:
I have a tendency to break cut taps in stressproof, always on retract in the lathe.

What kind of cut taps are you using? Spiral point? Spiral flute? How deep are you tapping?

Cole2534 · Feb 3, 2021

Mtndew said:
What kind of cut taps are you using? Spiral point? Spiral flute? How deep are you tapping?

Spiral flute. 1/4-20, 1/2" deep threads, 1" deep hole.

Ended up drilling to 1-1/4" deep with a #6 and had no issues usong a spiral point.
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DanielG · Feb 3, 2021

Cole2534 said:
Spiral point. 1/4-20, 1/2" deep threads, 1" deep hole.

Ended up drilling to 1-1/4" deep with a #6 and had no issues.

Spiral point taps are for through holes; they shoot the chips forward. Spiral flute taps are much better for blind holes.

Cole2534 · Feb 3, 2021

DanielG said:
Spiral point taps are for through holes; they shoot the chips forward. Spiral flute taps are much better for blind holes.

I should have been more clear- I was breaking spiral flutes, the spiral point with extra depth lives.

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Mike1974 · Feb 3, 2021

Cole2534 said:
I should have been more clear- I was breaking spiral flutes, the spiral point with extra depth lives.

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At least by hand (don't have any real info), spiral flutes seem to require more torque so maybe that is a reason?

Milland · Feb 3, 2021

Mike1974 said:
At least by hand (don't have any real info), spiral flutes seem to require more torque so maybe that is a reason?

I think they require more torque because they use what's essentially a bottoming chamfer length to get the chips formed in a way that (ideally) they flow up the flutes - bigger, fewer chips.

A more traditional chamfer length like on a spiral point would give more, thinner chips, making it easier to clog the flutes.

triumph406 · Feb 3, 2021

Best way of answering your question is to buy a form tap and try it out.

If it was me I'd use a spiral point tap and play with the hole dia and depth as you indicated in post #8 Also I'd use a coated tap, TICN coatings seem to work well.

triumph406 · Feb 3, 2021

DanielG said:
Spiral point taps are for through holes; they shoot the chips forward. Spiral flute taps are much better for blind holes.

Spiral flute taps have a smaller cross section so are easier to break. I avoid using them, unless I really have to.

Mtndew · Feb 3, 2021

triumph406 said:
Spiral flute taps have a smaller cross section so are easier to break. I avoid using them, unless I really have to.

They are excellent taps, as long as you don't need to tap very deep. Notice how every mfg's video only shows their spiral flute taps going minimal depth? Like who the hell is using a 1/2-13 bolt with 3/8" of thread?

Once you go deeper than the flutes, chips like to wrap around the tap and that makes them snap in half.
Great taps, limited usage unfortunately.

triumph406 · Feb 3, 2021

Mtndew said:
They are excellent taps, as long as you don't need to tap very deep. Notice how every mfg's video only shows their spiral flute taps going minimal depth? Like who the hell is using a 1/2-13 bolt with 3/8" of thread?

Once you go deeper than the flutes, chips like to wrap around the tap and that makes them snap in half.
Great taps, limited usage unfortunately.

That's pretty much been my experience.

Cole2534 · Feb 3, 2021

Mtndew said:
They are excellent taps, as long as you don't need to tap very deep. Notice how every mfg's video only shows their spiral flute taps going minimal depth? Like who the hell is using a 1/2-13 bolt with 3/8" of thread?

Once you go deeper than the flutes, chips like to wrap around the tap and that makes them snap in half.
Great taps, limited usage unfortunately.

EXACTLY. With long, stringy chips it's less of an issue. With short, crumbly chips they pack the hole, IME, and block egress.

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