Thread: How to avoid tool runout with ER collet

Originally Posted by nearnexus

Gawd, look at the machine marks in the first picture on the collet chuck spanner flats. LOL. That's hardly confidence inspiring.

Yes I agree !

Hold the collets up to the light and look through each slot for crud etc.

I've just looked at a couple of unused ones of mine and found some swarf in the slits, also a slight harrage on the inside of the small ones. I can't push a 3mm dowel through either 2-3 or 3-4 ones. I'm going to have to check them all.

The two pictures you have above showing the cutter you have the cutter too far into the collet. In those pics if you tighten it up the nose of the collet will be clamping on the flutes of the endmill and not on the round shank. That is a big no no and would be a big contributing factor.

I have the cheapest set of er collets i could find from a Chinese seller and ive never had a problem with them.

One thing i have learnt is that if the collet does not tighten firmly and positively from loose to tight (after take up) in 1/4 turn then theres something wrong. Either theres swarf in the way or the tool is not seated properly.

Simon

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Originally Posted by BobL

Knowing the sizes of the run outs you have measured with different chucks and collets etc may be useful - there may be a systematic pattern amongst all those measurements but without the data we are really just guessing
When you say some run outs exceed the limit of the indicator, what is the limit?

I can't really see a systematic pattern in the runout. Sometimes I can be reasonably close, others I can have over 0.5mm runout (the limit of my test indicator in one direction)

Originally Posted by MasterSpoon

The two pictures you have above showing the cutter you have the cutter too far into the collet. In those pics if you tighten it up the nose of the collet will be clamping on the flutes of the endmill and not on the round shank. That is a big no no and would be a big contributing factor.

In that picture I was trying to place the end mill as far into the cutter without touching the flutes. It was impractical for cutting due to limited stick out and ultimately made no difference.

I can't push a 3mm dowel through either 2-3 or 3-4 ones.
Ahhh - really?
The 2-3 collet should be a neat fit on a 3 mm dowel, and should close down to 2 mm. The 3-4 should take a 4 mm dowel neatly and close down to 3 mm. If you cannot get a 3 mm dowel through either of them, then something is REALLY wrong.
With all due respect, you need to get someone else who has used collets a lot to look at the collets. I can't help feeling it is something really simple!

Cheers
Roger

Judging by the poor machining on the collet chuck it made me wonder if the thread is bad, causing a loose fit with the nose cap.

The thread is actually very important/instrumental in pulling the front taper into position correctly. Any slop is bad news.

I doubt that it is the thread: the primary reference surface is the long taper. The short steeper taper at the front comes next, but that is definitely secondary. Frankly, I suspect that the thread could be as rough as guts (well, almost) and the collet should still work.

Cheers

Originally Posted by rcaffin

I doubt that it is the thread: the primary reference surface is the long taper. The short steeper taper at the front comes next, but that is definitely secondary. Frankly, I suspect that the thread could be as rough as guts (well, almost) and the collet should still work.

Cheers

I'm expecting the long taper the be the issue now as well. I've noticed that the collet can wobble a bit (when pushing on the tool) until the nut is tensioned quite a bit. I don't think the taper angle on the chuck is the same as the collet.

The HM47 comes with a #3 Morse taper. Morse taper is OK for a drill, but a seriously bad idea on a mill as it can vibrate loose and let the cutter and adapter fall out. OK, so they put a #3M to ER32 adapter in - which is a recommended accessory from H&F with that machine. So first remove the adapter and clean both it and the taper it goes into, replace and tighten up the pull rod with a serious spanner. Then check it for wobble and TIR.

I don't think the taper angle on the chuck is the same as the collet.
That would be almost unbelievable - unless it is not an ER32 holder. There are other sorts of collet systems, some of them not too distant, but I would find it hard to imagine that you would find an ER32 nut fitting onto one.

But, that is still worth exploring. Can you borrow a #3M to ER32 adapter from someone else and try fitting it to your machine? Can you try borrowing a single good ER32 collet from someone else and try fitting it?

It would be a sad story if the person selling the HM47 did so because he could not get cutters to fit stably himself, because somewhere back up the history a previous owner (or even the vendor) screwed up with the adapter. Highly unlikely imho, but something is screwy here.

Cheers
Roger

Originally Posted by rcaffin

The HM47 comes with a #3 Morse taper. Morse taper is OK for a drill, but a seriously bad idea on a mill as it can vibrate loose and let the cutter and adapter fall out. OK, so they put a #3M to ER32 adapter in - which is a recommended accessory from H&F with that machine. So first remove the adapter and clean both it and the taper it goes into, replace and tighten up the pull rod with a serious spanner. Then check it for wobble and TIR.

I have checked the runout on the inside taper of the adapter with the drawbar tight and found about 0.02mm runout.

I don't think the taper angle on the chuck is the same as the collet.
That would be almost unbelievable - unless it is not an ER32 holder. There are other sorts of collet systems, some of them not too distant, but I would find it hard to imagine that you would find an ER32 nut fitting onto one.

What I meant was that the adapter angle may be slightly different to the collet, so it's not gripping the full length of the collet. This may be due to poor machining tolerances?

It would be a sad story if the person selling the HM47 did so because he could not get cutters to fit stably himself, because somewhere back up the history a previous owner (or even the vendor) screwed up with the adapter. Highly unlikely imho, but something is screwy here.

I bought the machine new from hare and Forbes, but I don't think it's a machine issue. I have other tooling (a carbide face cutter) that seems fine.

I do appreciate all the feedback

Mat

If you have lathe? and have a length of ground stock to suit 1 of your collets, put the stock in your lathe and check and note the run out of the stock, now fit your collet/chuck to the stock in your lathe and check what run out you have, note the high spot and turn the collet chuck 180 deg and check it again.
You get an idea of whether or not to bin the collet chuck.

Cheers, shed

It could also be a batch of dodgey collets

I bought the machine new from hare and Forbes,
Aha. Are they anywhere near you? Can you take the problem - or at least the collets and the adapter, back to them for checking?

but I don't think it's a machine issue. I have other tooling (a carbide face cutter) that seems fine.
Yeah, but what is the fitting for the face cutter? Morse taper? If so, that tells you zero about the adapter.

Cheers
Roger

Originally Posted by rcaffin

I can't push a 3mm dowel through either 2-3 or 3-4 ones.
Ahhh - really?
The 2-3 collet should be a neat fit on a 3 mm dowel, and should close down to 2 mm. The 3-4 should take a 4 mm dowel neatly and close down to 3 mm. If you cannot get a 3 mm dowel through either of them, then something is REALLY wrong.
With all due respect, you need to get someone else who has used collets a lot to look at the collets. I can't help feeling it is something really simple!

Cheers
Roger

Hi Roger,
I really should re-read my posts more carefully
That should have read "I can't push a dowel through either 2-3 or 3-4 ones."

Sorry about that. I'm going to blame it on old age. I wasn't too happy about discovering the harrage on the inside edges. I've since checked and found that all my collets have some. Particularly the ER16 ones I use on my drill grinder.