Accuracy of cheap ER collets

Hi. I feel this is a beginner question. I just finished restoring a Schaublin 22 mill, and have barely made "first cut" I have just purchased some tooling from SanTool in Germany, received it today. Got lots of nice stuff, and also purchased an ER32 collet set. I already had the collet holder, ISO 30 (unknown brand) and one 12 mm Rego Fix collet that came with the mill

The ER 32 set was not terribly (round €100) but I expected the fit to be better It is a metric set with two mm range pr. collet. So for instance there is one 9-10mm collet, and a 10-11mm.

A 10 mm end mill slides neatly into the 9-10mm collet alone, but once I mount it in the nut, there is no way I can fit the end mill. The 10-11 is way to big, and the end mill will only sit in the holder when I have tightened the nut hard. Milling works fine, but once I loosen the nut, the end mill falls out.

Is this the way things work, or is it a result of too cheap, probably Chinese collets?

My RegoFix collet fits precisely even after the collet nut has been mounted on the collet

Apeciate any insight into my little collet mystery.

Cheers

There was a long, and very interesting discussion about this a while ago.

I will see if I can locate the thread.

MichaelG.

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Edit: Here you go

http://www.model-engineer.co.uk/forums/postings.asp?th=116912&p=1

Edited By Michael Gilligan on 31/08/2016 23:01:10

Not bringing that thread up again Mg but the red and green zones due to collapsing the collet means that there will always be some read unless both collet hole and cutter shank are exactly the same size. In practice grip will be better with a collets max size fitted but there will still be a degree of point contact that just gets worse as it's clamped down to smaller sizes.

Anyway - I can usually change a cutter by mostly unscrewing the nut. In practice I find it's often easier to unscrew it completely. The problem is that if the cone of the collet contacts the taper in the chuck it self tightens and say a 10mm tool in a 9-10mm collet it's a size on size fit or very close to it. Fit 3/8 in the same collet and it can be inserted and with drawn easily but the ejection mechanism on the nut still needs to act so just loosening the nut wont do anything.

More run out when this collet is fitted with 3/8" cutter? No afraid I wouldn't agree with that unless something has seriously worn worn on one or all of the contact faces.

John

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Thanks Michael, that was an interesting read, but debated more on the run out than my fitting problem. Although, it did confirm that a 10-9 collet has the nominal size for a 10 mm end mill. The Regifix link held interesting info as well.

I am just not able to push that 10mm end mill into the 10-9 collet once the nut is snapped in place, let alone when fitted into the chuck. If I try hard, I'm just blemishing the shank. Same story for my 20-19 collet and a 20 mm end mill and others. They are just too small, and the shank of the mills measures precisely to the numbers expected.

Arnljot

Hi Arnljot,

I have never come across your problem with my cheap ER collets. Have you tried with another nut? Seems to me that the nut is compressing the collet a bit, or the "groove" in the collet is not deep enough.

I use Ball Bearing nuts from ARC, and the work very well.

Thor

I do find some shanks are larger than others, for example my Dormners slip into the collets and stay there but don't need much force to move them, I have cheap far eastern ones that are very firm and need a good tug to get them in and out of the collet, I have others that if you are not careful will drop onto the mill table when the nut is undone.

It may just be that you have a cutter that is a bit oversize or at the upper limit of 10mm. or your collets are a bit undersize.

Given the quality of the mill why skimp on cheap collets, ones to match the quality of the mill are probably 4-5 times the cost and there is a reason for that.

It could be a problem, with the nut rather than the collet. The nut should only hold the collet loosely, a 'rattling fit' and should not close it up at all and so should not affect you being able to push a cutter into it.

It does sound like either the nut's locating collar is tight or the groove in the collet is too shallow.

Others have had problems with wrong assembly, just to be sure you are just lightly clipping the collet into the internal eccentric ring, not forcing it?

Neil

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Don't spoil the Ship for a ha'p'orth of tar.

MichaelG.

My mate Barrie had the same problem which turned out to be the nut was undersize. Swapped the nut and everything worked fine. If you have the same problem expensive collets wont fix it.

regards Martin

Certainly a mill of Schaublin class demands collets of equal class. Regofix , Rohm ect, or if you really want to "push the boat out " Fahrion. of course all these demand the same class of chuck. which gets very spendy or in the case of Fahrion very very spendy.   As Michael said "don't spoil the ship for a ha'peth o tar.

cheers.

Edited By Raymond Anderson on 01/09/2016 08:54:57

Thanks for all the suggestions. I have measured the shanks of the end mills I'm using, and they measure spot on the value in question, whether 10 or 20mm. So it is not variance in shank size that is the problem.

I have thought about that the nut might be the culprit, I do have another tool holder on the way, so then I will be able to test if this makes a difference. I measured the inside bore of the collet before and after snapping it into the nut. While very close to nominal size before snapping it into the nut, the reduction in bore size afterwards was surprising, close to 50/100th of a millimeter smaller.

Regarding the quality I have chosen: Of course wouldn't we all liked to buy the best there is to find in the marked when it comes to tooling. Since this is my first mill, there is so much equipment I need, so I had to compromise some on the quality on certain purchases. I buy quality where it counts, and didn't think cheaper collets would be a problem. However, based on the shank sizes on the various mills I have purchased, I did not really need a full 19 (or 20) piece collet set to start with. In retrospect, I would rather have bought fewer quality collets, and this might be what I end up doing.

I suspect your problem is precise collets and the fact that they are ER32 - a lot more metal to bend than say my ER16's which is all that is needed for up to 10mm / 3/8". I also have a set of ER25's and a collet chuck. These are much more like you have mentioned when used for smaller sizes. I have thought about getting a bigger size but due to the collapsing pressure needed on say an ER40 I wont be buying any that go below the ER25 size and even wonder about that.

For smaller sizes to make things easier you could use an ER16 extension collet chuck but I think you may find that you will still have to remove the nut and collet to change cutter. The extension collet shanks are usually a touch under size except the metric and imperial sizes that are very close together. So should be easier to take in and out.

John

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Are we all sure that ER collets cover a range of two millimetres? The 'ordinary' set I bought from Chronos has collets in 1mm steps - ie there are 8-9, 9-10, 10-11, etc. So perhaps the problem relates to the OP's set requiring full closure for half the metric sizes - when in my experience, and looking at the design, the 'best' fit is when the collet is squashed the least.

By 'ordinary' I mean there was nothing special or super fancy claimed, just an off the shelf full set.

Cheers, Tim

Nice to see that I'm not the only one having this problem. My original collet chuck has a run out of .004", which is a phenomenal amount, so I bit the bullet & ordered a new chuck from my usual supplier. this new chuck when fitted has the same problem, I have fitted various size cutters into it & still have same run out. I did some tests to check where the fault could lie...

The run out of my mill spindle is .0005" ( 1/2 thou' ), with the new collet chuck, with the same dti set up, it showed the internal taper run out of .004-5 thou', when fitted with either a 3/8 tool steel or 12 mm cutter the same run out shows up. To me this indicated that the internal taper didn't run co-axially true with the MT2 taper.

I have raised the question with the supplier via an e mail plus a couple of video clips, they requested I sent the chuck back for investigation, the response from them was that their investigations revealed no run out greater than .001"... ( their video clips showed no discrepancy ), so I am at a loss at the moment. I have requested could they provide any further suggestions, also possibly an exchange / replacement chuck, I await their reply

George.

As Tim says they only cover 1mm range

10-9mm is 10mm max down to 9.01

11-10 is 11mm down to 10.01

But I don't like closing them right down unless I really have to.

Arnljot, I would just like to say I really enjoyed your videos about the Schaublin 22 on Youtube - I've just taken on a Schaublin 53N with some electrical damage and it was very interesting to see your work!

**LINK**

Out of interest have you tried a 12mm tool in the Regofix collet?

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Tim,

Going back to the opening post ... Arnljot wrote:

I believe what he actually meant by this is that the range is contiguous, and [in the example quoted] 10mm is 'available' in two collets.

MichaelG.

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Reference: San Tool

http://www.shop.santool.de/en/collets/din-6499/precision/er-32-470-e-up.html

Edited By Michael Gilligan on 01/09/2016 10:11:02

Yes, as stated in the OP, a 12 mm tool fits perfectly in the Regofix 12mm. Same holder and nut.

The fact that this is well used might have something to do with it. As Ajohnw says: "I suspect your problem is precise collets and the fact that they are ER32 - a lot more metal to bend ". Just like new shoes, they hurt in the beginning, but as you wear them in, they fit much better

Arnljot

I would only expect precision if the collet is a slide fit on the cutter shank; too much ( ie more than 1/2 mm) looseness is likely to reduce parallel gripping accuracy. Although ER collets have a greater gripping range than this it is not wise to make full use of this if it can be avoided. I have many cheap ER collets from ArcEuro and have found the accuracy to always be good Colin