Snapping M4 taps

KristianSilva · Aug 29, 2018

Hi,

I have a problem with snapping M4 taps, I think what is happening is that after the first hole or two swarf is building up on the tap and causing the tap to jam up with swarf. How can I clear this swarf?

Material is mild steel and the tap is a spiral flute tap for steel and im using the correct cutting data.

Thanks

dandrummerman21 · Aug 29, 2018

Turn spindle on clockwise and counterclockwise really fast several times usually clears chips off of spiral flute taps.

If it doesn't, maybe rig up an airblast and do the same thing.

Another idea that might not work but just came to me, put a wire brush on the table somewhere and run the tap counterclockwise against it, it might pull the stringy chips off of the tap?

I learned the hard way with spiral flute taps, don't peck tap. You will end up with 5 stringy chips all packed in the flute all at once, and thats a lot harder to get rid of than 1 long one.... if it doesn't break while tapping first.

Mtndew · Aug 29, 2018

KristianSilva said:
Hi,

I have a problem with snapping M4 taps, I think what is happening is that after the first hole or two swarf is building up on the tap and causing the tap to jam up with swarf. How can I clear this swarf?

Material is mild steel and the tap is a spiral flute tap for steel and im using the correct cutting data.

Thanks

How deep are you going with the spiral flute tap? In my experience, they aren't much good at deep holes, the chips will wrap around the tap. If you're going 1xD to 1.5xD then you're fine.

NAST555 · Aug 29, 2018

For starters what is your retract height after each hole?
I assume you are rigid tapping? Make your retract height higher so that it spins CCW longer out the hole. Normally helps me to get rid of the chips on the tap.

KristianSilva · Aug 29, 2018

Mtndew said:
How deep are you going with the spiral flute tap? In my experience, they aren't much good at deep holes, the chips will wrap around the tap. If you're going 1xD to 1.5xD then you're fine.

Im going 2xD + 3 pitch lead so 10.1mm.

NAST555 said:
For starters what is your retract height after each hole?
I assume you are rigid tapping? Make your retract height higher so that it spins CCW longer out the hole. Normally helps me to get rid of the chips on the tap.

Yes I am rigid tapping, I am retracting to z100. as I have to clear a boss in between holes. How do I program the reverse spindle on a haas control whi;le still in a canned cycle?

Milland · Aug 29, 2018

Coolant mix richness and flow? Aimed right at the tap?

Are you rigid tapping or using a tension/compression holder? And what's the minor diameter of the starting hole? Are the holes clean, or could there be swarf still in the holes that conflicts with the tap entering and depth?

Peck tapping should be fine as long as you come fully out of the hole each peck and allow time for the shorter chip to be flushed off the tap.

KristianSilva · Aug 29, 2018

Milland said:
Coolant mix richness and flow? Aimed right at the tap?

Are you rigid tapping or using a tension/compression holder? And what's the minor diameter of the starting hole? Are the holes clean, or could there be swarf still in the holes that conflicts with the tap entering and depth?

Peck tapping should be fine as long as you come fully out of the hole each peck and allow time for the shorter chip to be flushed off the tap.

Coolant mix is at 10% and the coolant is aimed at the tap, however im working on a TM-1P so you could piss harder than the coolant...

I am rigid tapping. Im drilling the hole to 3.2mm for an M4 x 0.7 tap. Im pretty sure the holes are clean but thats something to check. The drill is going deep enough also.

NAST555 · Aug 29, 2018

KristianSilva said:
Im going 2xD + 3 pitch lead so 10.1mm.

Yes I am rigid tapping, I am retracting to z100. as I have to clear a boss in between holes. How do I program the reverse spindle on a haas control whi;le still in a canned cycle?

What I meant was how high does the tap retract above the part when it is still reversing out of the hole? So the start R value before you start tapping. I have found that letting it reverse a bit higher off the part with the coolant blasting directly at the tap takes 99% of the chips off.
As a rule of thumb I don't start the hole closer than 10mm above to let the chips get blown off. Most of the times that I see chips sticking to the tap I just increase this value a bit so that it gets a few more turns out of the part.

Milland · Aug 29, 2018

KristianSilva said:
Coolant mix is at 10% and the coolant is aimed at the tap, however im working on a TM-1P so you could piss harder than the coolant...

I am rigid tapping. Im drilling the hole to 3.2mm for an M4 x 0.7 tap. Im pretty sure the holes are clean but thats something to check. The drill is going deep enough also.

So why 3.2mm rather than 3.3mm for the pilot hole? That could be your problem right there.

And you should be able to improve coolant flow, do you have any blockages in the coolant lines from a buildup of chips? Do you have the coolant sump clean and no clogged traps?

Milland · Aug 29, 2018

I don't have any experience with the Toolroom mill series, not sure how their "following" errors are with regard to tapping. If there's a question, going to a holder with a little compliance may help with thread accuracy and tap life, unless you're trying to tap to the very bottom of the hole (which is bad design if that's what's called out).

guest · Aug 29, 2018

Form tap it.

mTeryk · Aug 29, 2018

Milland said:
So why 3.2mm rather than 3.3mm for the pilot hole? That could be your problem right there.

And you should be able to improve coolant flow, do you have any blockages in the coolant lines from a buildup of chips? Do you have the coolant sump clean and no clogged traps?

Agreed, my Drill and Tap table says a 3.3mm drill gives a 77% thread which is pretty tight for steel. 3.2mm drill is super tight.

Teryk

Milland · Aug 29, 2018

mTeryk said:
Agreed, my Drill and Tap table says a 3.3mm drill gives a 77% thread which is pretty tight for steel. 3.2mm drill is super tight.

Teryk

Yup, he needs to open up the hole diameter, and I agree that going to perhaps 3.35mm makes sense.

Gobo · Aug 29, 2018

Milland said:
Yup, he needs to open up the hole diameter, and I agree that going to perhaps 3.35mm makes sense.

77 percent thread. Wow! Give them 65 % and your troubles will fade.

DMF_TomB · Aug 29, 2018

some cnc have problems tapping above certain rpm, have you tried slower rpm ?

kenton · Aug 29, 2018

Any reason you can't use a form tap?

Mtndew · Aug 29, 2018

What the others have said, open up your hole to 3.3mm! :cheers:

Larry Dickman · Aug 29, 2018

the minor dia for a M4x.7 is 3.242 / 3.472

Milland · Aug 29, 2018

Hell, let's go to 3.6mm!

I kid, but 3.35mm to 3.4mm seems a better choice than 3.2mm.

cwtoyota · Aug 29, 2018

NAST555 said:
For starters what is your retract height after each hole?
I assume you are rigid tapping? Make your retract height higher so that it spins CCW longer out the hole. Normally helps me to get rid of the chips on the tap.

I do this too, in deeper holes (longer chips).
For a shallow tap operation I can go R = 0.2 but for the deeper holes I'll go as much as R = 1.0

Do you have air-blast? It actually helps to blow the chips and junk off of the tap if it's aimed correctly.
I have an aluminum job on the mill right now that has a bunch of 1.3" deep 1/2-13 holes, the air-blast made all the difference.

Snapping M4 taps

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