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Issues with spiral flute taps

I've seen this same issue on all the spiral flute taps I've used on deep holes irrespective of brand.

Yeah, I use spiral flute taps a lot and none are immune to it, however they are not all created equal in how bad they are for it.

I did one job where the IMC rep convinced me to buy a bunch of Iscar OneTap M16 spiral flutes and I swear every single fucking one chipped out like this after only a few holes. Switched back to my preferred Noris Salorex and didn't chip one.

Speed definitely helps as it works to form a more coherent chip and pull it out of the hole better.
 
Turns out the OSG HY-PRO HXL tap was a total let down. It would tear the threads a little bit no matter what I tried. They recommend 50-120 sfm in mild steel, I tried it at 50 sfm/ 300 rpm to keep it in low gear, I've never tapped in high gear on this machine, it scares me. I tried it at about 65 sfm/400 rpm which put it in high gear, it looked a little better but still tore the threads a little at the bottom of the hole.
I then tried it at 100 sfm/600 rpm which was a real pucker moment, but the threads didn't improve

My coolant concentration is at 10% so it should be sufficient for tapping.

I went back to the OSG A-Brand spiral flute taps. I would normally run them at about 33 sfm/200 rpm cause I'm a scaredy cat. OSG recommends 80-120 sfm. im running it at around 80 sfm/500 rpm for now with rapid tap and so far it's working great going full 2xD depth. Turns out I just gotta stop being such a little bitch :D. We'll see how many holes I get through before I start regretting my life choices.
 
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Maybe backing up a three or four turns then running forwards a couple or three turns would loosen the swarf in the tap so it all comes out cleanly without trying to re-cut.

Ages ago I managed to do the same edge chipping thing when manually tapping a deep hole with a spiral flute tap in something unfriendly.

Despite plenty of lubricant.

Thinking about the problem before rushing in and destroying another tap I recalled that the tap had briefly gotten pretty stiff partway out before freeing off after a turn or so. Not tapping thread stiff but getting up that way. Remembering similar issues with normal hand taps if you go too far before backing off to clear the flutes part way through the job necessitating a forward / back part turn technique until the jam clears I figured the same sort of thing might work in this case.

So for the next hole I carefully wound back until the tap started to stiffen, went forward a bit before coming back until it got stiff again. Probably took two or three cycles before the jam cleared. I've been alert to the problem ever since. If using one of my Pollard tapping heads I habitually give a quick burst of forward movement part way through backing out of a deeper hole.

Just in case.

But I don't do production. The job takes as long as it takes so I can get away with this sort of silly, "Mr Cautious", stuff.

Seems logical that the problem is because you are tying to clear a full depth chip all the way up. Reverting back to hand tapping I noticed that the stick on back out of deeper hole was always more likely when just using a second cut tap for the whole job rather than starting with a first (taper) tap. Obviously with a taper tap most of the swarf is not full depth whilst with a second, with its much shorter leading taper, most of the swarf is full depth so more to jam.

Clive
 
Turns out the OSG HY-PRO HXL tap was a total let down. It would tear the threads a little bit no matter what I tried. They recommend 50-120 sfm in mild steel, I tried it at 50 sfm/ 300 rpm to keep it in low gear, I've never tapped in high gear on this machine, it scares me. I tried it at about 65 sfm/400 rpm which put it in high gear, it looked a little better but still tore the threads a little at the bottom of the hole.
I then tried it at 100 sfm/600 rpm which was a real pucker moment, but the threads didn't improve

My coolant concentration is at 10% so it should be sufficient for tapping.

I went back to the OSG A-Brand spiral flute taps. I would normally run them at about 33 sfm/200 rpm cause I'm a scaredy cat. OSG recommends 80-120 sfm. im running it at around 80 sfm/500 rpm for now with rapid tap and so far it's working great going full 2xD depth. Turns out I just gotta stop being such a little bitch :D. We'll see how many holes I get through before I start regretting my life choices.
The youngest of my operators used to be scared of cutoff tools on the lathes. Everything he programmed had a .002 feed per rev on the cutoff. He kept blowing up inserts not realizing he was running them way too slow. Once I realized what he was doing I had him watch me and let him see the load and how much better it broke a chip. He is now getting rather daring with it. I recently tried the YG1 3/4-16 TiN coated spiral flute taps with through the tool coolant and have been very pleased. Our stuff is mainly bar fed so technically all the holes are blind and up to 2.5 deep. It really has helped us not kill so many taps.
 
I recently tried the YG1 3/4-16 TiN coated spiral flute taps with through the tool coolant and have been very pleased. Our stuff is mainly bar fed so technically all the holes are blind and up to 2.5 deep. It really has helped us not kill so many taps.
I'll have to try one of those out sometime.
 








 
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