Quad Lead Thread Trouble

[441Sky]

Looking for info to tap a 8-32 Quad Lead H3 into 303 stainless. (Drill size, speed and feed per rev) on our Mazak Multi 610. Taps keep braking on contact at .125 per rev.

Thanks

 

[Gobo]

Do you chamfer before tapping? Rigid or floating holder? What percentage of thread are you shooting for?

 

[Bobw]

Are you running a 10-32 tap, and just trying to feed it 4 times as fast?

 

[Scruffy887]

Maybe just me but??? #8 diameter and 4 start thread? Where does 8/32 come from?

 

[441Sky]

Yes the hole is chamfered and using a floating holder. Looking for 40% thread to a loose fit.

 

[TeachMePlease]

What tap, specifically, did you buy? Give us the part number and/or a link to the website.

 

[Gobo]

Yes the hole is chamfered and using a floating holder. Looking for 40% thread to a loose fit.

If you can rigid tap, that is preferable.

 

[TeachMePlease]

Are you running a 10-32 tap, and just trying to feed it 4 times as fast?

It never would have even occurred to me to ask that question... But once you brought it up...

 

[MaxPrairie]

Looking for info to tap a 8-32 Quad Lead H3 into 303 stainless. (Drill size, speed and feed per rev) on our Mazak Multi 610. Taps keep braking on contact at .125 per rev.

Thanks

Thread milling sounds like it would be easier.

 

[dandrummerman21]

Thread milling sounds like it would be easier.

I don't think a 4 start #8 thread could be thread milled. Seems the thread form would be all wonky because the lead is too high.

 

[mhajicek]

+1 on the rigid tap. I bet the floating holder has too much give for that steep lead.

 

[Booze Daily]

I would love to see a pic of this tap.

 

[Gobo]

I don't think a 4 start #8 thread could be thread milled. Seems the thread form would be all wonky because the lead is too high.

Your right. I forgot about the4 start.

 

[Conrad Hoffman]

All the nuts for things like that I've seen have been molded. I can't imagine how a tap could work. It would be more like broaching with a twist!

 

[MaxPrairie]

I don't think a 4 start #8 thread could be thread milled. Seems the thread form would be all wonky because the lead is too high.

Not sure how it would look. I guess when I’m not sure how a tap will work I hand tap the first hole and see how it feels then decide on feed n speed. It would be nice if there was a #8-8 tap then you could rigid tap to depth 4 times and bump the R plane up 1/32 each time and drop the Z the same amount.

 

[dandrummerman21]

Not sure how it would look. I guess when I’m not sure how a tap will work I hand tap the first hole and see how it feels then decide on feed n speed. It would be nice if there was a #8-8 tap then you could rigid tap to depth 4 times and bump the R plane up 1/32 each time and drop the Z the same amount.

So, I had a stupid idea, and then a less dumb one. But someone with a bit more experience boring threads would have to chime in about it.


Why not single point the thread? with such a coarse pitch you'd have to have a threading bar that was relieved underneath the cutting face so it didn't rub. But this is basically what you'd do if it was a "normal size" and not a tiny ass thread.


But my stupid idea (maybe not so stupid!?) would be to take the same tap that you're breaking, grind off all but one of the flutes off of it, and use THAT as a "single point tool" with a threading cycle. At the very least, the required clearance should be ground well enough into the tap.


Thoughts?

 

[EmGo]

Why not single point the thread?

Not necessarily but probably, the angle is going to be too steep. In a lathe you can tilt the tool over far enough so it doesn't rub on the thread and run it though along the thread but in a mill, it has to rotate around the spindle axis while making the thread, so probably going to have severe interference problems on the heel.

But one could always try ...

Tap seems the easiest to me.

 

[Bobw]

Why not single point the thread? with such a coarse pitch you'd have to have a threading bar that was relieved underneath the cutting face so it didn't rub.

It would have a tiny little shank.. If everything was perfect, the biggest the shank could
be is .115.. probably end up around .090" for clearance. It would just be miserable..

On the tap idea, you would have to lose a lot of the tap. Not just grind the teeth off.

I also wonder what would happen on the deceleration on the end of the thread? Would
the Z feed slow down enough to bind the tap before retracting. Also.. The decleration
wouldn't happen on just the last thread, it would happen on all of them, and probably make
a big mess.

Only one way to deal with a thread like this.... No Quote.

Edit: Thanx to threadpal. 15.476 degree lead angle.

 

[dandrummerman21]

Not necessarily but probably, the angle is going to be too steep. In a lathe you can tilt the tool over far enough so it doesn't rub on the thread and run it though along the thread but in a mill, it has to rotate around the spindle axis while making the thread, so probably going to have severe interference problems on the heel.

But one could always try ...

Tap seems the easiest to me.

But I thought a Mazak multi 610 was a lathe?

It would have a tiny little shank.. If everything was perfect, the biggest the shank could
be is .115.. probably end up around .090" for clearance. It would just be miserable..

Another question to the OP: how deep are you trying to go? a .090 bar doesn't seem like it would be too bad if it was a quarter inch or less deep. (I say that, having no experience with a bar that small, and little experience on a cnc lathe)

At least it is 303 and not 304 or worse.

 

[Philabuster]

But I thought a Mazak multi 610 was a lathe?

Live tool lathe.