Excentric collet

Got some free time just now, so have fired of an e-mail to Regofix and Sandvik Coromant as regards the holding power of a collet when closed down to the lower end of it's range.

Will post the answer once it's received.

Just an observation. I have yet to see a tolerance on the bore of an er collet and if there was where would we obtain the cutter that was an exact fit in it ?

John

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Can't answer that, but for instance 16mmØ shank would never be dead nuts on 16mm It would be under [something like 15.997] never over. So me thinks a 16/15mm collet would be a few µ over the 16. or they may even be toleranced from the lower Ø. I have no idea on that. But later on I am going to insert a carbide bar that I had specially made,into a 20 Ø ER32 and see how much [if any] it expands the collet. The bar in question is 19.998 Ø

Raymond: Thanks for taking the time and trouble to get this information from the manufacturers. Most interesting, and I've certainly learnt a lot.

Andrew

Hi Andrew, No problem, I too have found it very interesting and infomative. It just goes to show how [ when using top class ER collet chucks ,collets and closers ] just how accurate the system is. The TIR figures that one can look forward to seeing are superb. Iv'e always been a fan of the ER system even for workholding, although im not blind to the fact that there are collet systems that are better for that aspect. The biggest bugbear I have with it from a "workholding" aspect is it's not very good at short length parts [parts always must be inserted at least 2/3ds of the collet length] although that can be solved by turning a plug the same Ø as the part. Its just not very convenient.

I am now going to try and find out the " bore tolerance " to try and answer John's query.

cheers

In my experience ER collets are a 'push fit' on cutters with the matching nominal diameter. Given the inherent flexibility of the collet, I would be surprised if they are toleranced to be bored oversize.

It will be interesting to see what you find.

Perhaps a short article for MEW summarising all this information could be a useful outcome of this thread?

Neil

Tormach have investigated pull out values for collets. Their report is useful reading for anyone using collets.

**LINK**

The important point for this thread is suitable lubrication on the correct surfaces. I wonder how many of these run out checks are being carried out with suitably lubricated surfaces. It may make a difference to the TIR values. It would be a good subject to include if an article is written for MEW as suggested by Neil.

Martin

Hi Folks, I could put the pdf of the ISO 15488 / Din 4699 into a album but i'm not sure how. So in answer to Ajohnw's question re bore tolerance,, The bore of an ER collet is to H7 tolerance.

Also as an aside, you can also get "ETS " collets which fit into an ER chuck, but use a different closing nut [same threads obviously ] The accuracy is slightly better than ER collets

cheers.

.

Raymond,

Regrettably ... We mere mortals can't post pdf on this site.

MichaelG.

Would there be any way I can post it ,as it is a very interesting document and details lots of good info as regards testing. Taking numerous photos does not seem like a very efficient way of doing it [if indeed it is possible ].

Put it on a cloud server such as Dropbox and post a public link here.

Russell.

Hi Russell, Went to the Dropbox website, and even for a free 30 day trial they want credit card details,which , im not happy about giving [ not for a "free " trial anyway.]

Cheers.

Google search first result seems to send you to the business site: Try this **LINK**

Rod

Many thanks Rod, I have now downloaded "Dropbox " and put the PDF into my box Can anyone tell me how to post a link to the box, on here ? Thanks.

https://www.dropbox.com/s/bhbzbp74byr9zan/standard2841.pdf?dl=0 I think I have managed to figure it out.

Seems to work ok, but you have to copy first. So it's not the type of ink that you simply click on. I must still be missing something. But at least it works.

Try this, Raymond

**LINK**

MichaelG.

Click on the globe-with-chain symbol then paste the link into the pop up box

**LINK**

Thanks for the data.

Rod

Hi Michael, thanks for that works perfectly thanks also to Rod. Hope the doc is of some use to folks. I find it very interesting, [but then again i'm sad ] Everything one needs to know about ER collets is in there.

Cheers.