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Issues with spiral flute taps

MillGuy88

Aluminum
Joined
Mar 13, 2024
Location
Saskatoon
I'm having issues with larger spiral flute taps from 5/8" to 1-1/8", anything bigger and I use a thread mill. It seems that the chips coming out of the hole are getting wraped around the tap and chipping it while trying to re-cut the stringy chips. 1/2" taps and smaller dont seem to have any problems, I'm assuming because the string chips are a lot thinner and weaker.

In the last 2 photos, you can see where a chip got jammed in between the thread and cutting tooth, actually cracking the tap.

I'm using a large CNC Horizontal Boring Mill so gravity is constantly pulling the chips in one direction and I'm wondering if that could be part of the problem. These are quality OSG taps. I have no problems when I peck tap so I get the same results when using just a plain old cheap plug tap, but peck tapping is exponentially slower.

Has anyone else experienced this same issue?
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How deep are you tapping? I've found that these kinds of taps don't like tapping very deep because of this very issue. They seem to be good for only the length of the thread on the tap at best.
They're great for shallow holes. That's why in product videos MFG's only show them tapping a shallow hole.
 
If you're going twice the diameter there can't be much room for the swarf to escape past the flutes. I don't do much in the range you're speaking of but have done a number of 5/8" and 3/4" holes to more than twice the diameter depth without problems.

However, I've always done them on a vertical mill with reduced shank taps. The swarf stayed intact and came out of the hole in one piece. The last ones were done with YG1 taps.
 
I don't believe the issue is going to deep and packing the flutes with chips or swarf. I think it's that the chips are getting wrapped around the tap before it even gets past the cutting teeth judging by where on the tap it is getting damaged.

I recall seeing an advertisement not too long ago for YG1 taps with chip breaking. I might have to try one out when my current ones wear out.
 
I'm usually tapping at least twice the thread major dia. deep.
Tap drill 7/16" or better.
2" of thread, you could do a 45% thread form and still break the bolt off before you stripped it out.
I did 10' linear tapping through 2" plate a few months ago on a day, and it was tough to start.
I went to 45% thread after the first few holes had problems, and did the entire pile with a regular plug tap in the machine, flawlessly.
 
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You might want to view this OSG video regarding 'speed' when tapping. Obviously, the feed is fixed. The video does not show tapping depth to which you need to do. The chipping of the tap is probably occurring during reversal & retraction of the tap...re-cutting the spiraling chip as you state.
 
I have used these same OSG taps for making 5/8-18 holes
and had a different weird problem. Material was 3/4 1018 plate.
The resultant thread would allow a bolt to screw in from one end
almost all the way, and then bind up. You could freely screw the
bolt in the other side of the plate, and it would again bind up, almost
all the way through. It turns out, the tap was getting a little bit
dull, very usable, but used a bit. This extra force was making the
spiral of the tap "unscrew" a bit, and the pitch was being effected.
So it was really cutting 18 + threads per inch. You could back out
the tap ok, but it was not correcting the pitch error upon withdrawl.
Running the tap in forwards again corrected the problem.
So be careful with those spiral flute taps unwinding a bit under
extreme twist.

-Doozer
 
Tap drill 7/16" or better.
2" of thread, you could do a 45% thread form and still break the bolt off before you stripped it out.

I'm having issues with larger spiral flute taps from 5/8" to 1-1/8", anything bigger and I use a thread mill. It seems that the chips coming out of the hole are getting wraped around the tap and chipping it while trying to re-cut the stringy chips. 1/2" taps and smaller dont seem to have any problems, I'm assuming because the string chips are a lot thinner and weaker.

In the last 2 photos, you can see where a chip got jammed in between the thread and cutting tooth, actually cracking the tap.

I'm using a large CNC Horizontal Boring Mill so gravity is constantly pulling the chips in one direction and I'm wondering if that could be part of the problem. These are quality OSG taps. I have no problems when I peck tap so I get the same results when using just a plain old cheap plug tap, but peck tapping is exponentially slower.

Has anyone else experienced this same issue?
View attachment 435229
On my Fadal, you have to make sure your gain is set correct.
And if your lashes aren't comped correctly, that can get you too.
That, or just use a floating holder and don't worry about it.
 
The fact that it's in the cutting edge leads me to believe the fracture is occurring during backing out as was already mentioned. Can you get air blast in there or a coolant flush before retract?

I've had spiral flute taps chip similarly during hand tapping but in 4140 norm, 3-1/2" deep. I was pretty sure chip jamming did that one too. (Emuge spiral flute 1-1/4" 12 NF)
 
This extra force was making the
spiral of the tap "unscrew" a bit, and the pitch was being effected.
This is something I'd have not thought of without a lot of broken taps. You've tainted my love for spiral flute taps just a bit. Thank you.
 
The spiral grind helps with chip formation on the way in but weakens the cutting edge causing fracture on the may out.
 
The spiral grind helps with chip formation on the way in but weakens the cutting edge causing fracture on the may out.
My thoughts exactly. Thus they have to be treated accordingly. Good lubrication and swarf removal becomes paramount for good tap life.

I've got 3 larger custom spiral flute, extended length taps on order right now, so good timing for this thread to pop up. (13/16" x 14 tpi 6" long)
 
I'm a rapid tap guy myself. We've had suppliers come in and give us some samples of other cutting oils, fluids and pastes to try, but they didn't seem to work as well in my opinion.
 
I think I may have found the solution to my problem. I was able to meet with some OSG Tool Reps at a local trade show and talk to them about my issues with their spiral flute taps. He said it could be because of the speed I'm using is on the slower side and I replied that I'm hesitant to increase the speed because I'm using a large horizontal mill and that the mass of the spindle makes it take a while to slow down and stop. If the tap breaks and I hit the stop button it will continue to destroy my hole for longer the faster I go.

His face lit up a little when mentioned that it was an HBM and said that they have taps specifically for horizontal applications. It's still a spiral flute but has a lower/faster helix angle and it's designed to break the chip into smaller pieces and works best with through spindle coolant.

The tap is an OSG HY-PRO HXL series tap (the 'H' stands for horizontal). I have a couple hundred M16 holes, 36mm deep in mild steel to do on an upcoming job. I hope it work well.

 
I think I may have found the solution to my problem. I was able to meet with some OSG Tool Reps at a local trade show and talk to them about my issues with their spiral flute taps. He said it could be because of the speed I'm using is on the slower side and I replied that I'm hesitant to increase the speed because I'm using a large horizontal mill and that the mass of the spindle makes it take a while to slow down and stop. If the tap breaks and I hit the stop button it will continue to destroy my hole for longer the faster I go.

His face lit up a little when mentioned that it was an HBM and said that they have taps specifically for horizontal applications. It's still a spiral flute but has a lower/faster helix angle and it's designed to break the chip into smaller pieces and works best with through spindle coolant.

The tap is an OSG HY-PRO HXL series tap (the 'H' stands for horizontal). I have a couple hundred M16 holes, 36mm deep in mild steel to do on an upcoming job. I hope it work well.

Nice!
Let us know how it works for ya.
 
Not the same application, but we used smaller size OSG Hy-Pro forming taps in 316 stainless. Worked like a charm. Job stayed set-up in the machine for over 20 years....bajillion holes were form-tapped. Drilling the deep hole was a different story. After trying multiple exotic drills, we settled on a taper-Length, turbo-flute drill with black oxide coating which was made by Bendix at the time. Half the price of the exotic drills, and twice the tool life.
 








 
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