# Small ER32 collet problem



## picclock (Feb 1, 2011)

I recently used a metric 3-4 mm collet for holding a 1/8" carbide endmill (couldn't quite jam it in a 2-3mm one). 

From the off, despite my best efforts it proved to be very difficult to lock into position. The first endmill just about stood up to it and after some use blunted and eventually broke. My second endmill lasted a matter of minutes before breaking on the edge of the material. I surmised that as it engaged the edge it got pulled downward from the collet which increased the depth of cut overloading and breaking the part.

I had the forsight to know I was likely to have issues and had already ordered a 1/8" collet for that purpose. It arrived this morning with the obvious benefit of only having to tighten with reasonable force. The unobvious benefit was the significant improvement in a mirror like surface finish. 

So I guess the moral is just cos it says 3-4 mm on the collet doesn't mean you should believe it - especially for the very small sizes.

Hope this is of some benefit.. .

picclock


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## bentprop (Feb 1, 2011)

This is indeed a problem with the ER colletts.Why don't they simply state 3 or 4mm,or whatever.However,they do have imperial collets,so I guess they didn't think people would mix and match.
Having said that,I do use a 13mm collet for 1/2",as I can't get imperial ones here.


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## Philjoe5 (Feb 1, 2011)

There is a pretty good guide for ER (and other ) collets here:

http://www.centaurtools.com/index.php?option=com_content&view=article&id=15&Itemid=43#2

According to their guide a 3 mm ER collet should be good down to 0.118". That applies to their particular product line but a difference of 0.007" between their lower limit and your 0.125" end mill isn't much. I suspect a lot of issues can affect the ability of the collet to clamp on their lower limit like quality of collet, end mill, wear, depth of cut etc.

Your experience is a good lesson for us. Approach the limits of these collets with caution. Thanks for sharing it

Cheers,
Phil


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## mzetati (Feb 2, 2011)

I noticed ER32 collets in the low range require a lot of strenght applied to be closed near their lowest limit. That sounds reasonable, as You have to flex much more metal when closing a 3mm collet to 2mm that when closing 20mm to 19.
There are some "odd" sized collets for sale ar arceurotrade.co.uk (usual disclaimer applies) in the ranges 2-1.5 / 2.5-2 / 3.5-3 mm.
Marcello


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## Blogwitch (Feb 2, 2011)

Your main problem is the collet closing nut, it is binding and jamming tight before you can get enough torque on it to complete the closing process. 

I can get full collet closing and tightening over the whole range of the collet marked size, no matter what size the collet.

Lubricating the plain closer nut on the inside taper can certainly help in that department, but the best cure is to buy a ball raced closing nut.

http://cgi.ebay.co.uk/ER32-collet-c...105?pt=LH_DefaultDomain_3&hash=item564194eb79


Bogs


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## Omnimill (Feb 2, 2011)

I second the Ball Race Nut, I bought one from Gloster Tooling and it's very good.

Vic.


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## oops again (Feb 2, 2011)

Hi 
  Bogs is on the money as usual. I made a collet chuck for ER 32 collets for the lathe and had the same problem of not locking up on the small sizes. After much !!#&* I found that the nut was bottoming out on the chuck. Fixed it by turning about 1mm off the end of the chuck so the nut didn't bottom out. The cheaper chucks could have the same problem. I suggest that you screw a collet up tight without anything in it. The segments should be all locked together. If not your problem is the same as mine was. 

  Cheers Dave


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## GailInNM (Feb 2, 2011)

For what it's worth, I HAD one ER16 4-3 collet that would not close tightly on 1/8 carbide shank end mills. I have 6 ER16 collet chucks for my mill and tried several of them. They are all name brand, mostly Vallenite. I have enough 4-3 collets to fill all of them and all the rest of the collets work OK. So it is possible to get an occasional bad collet. I could not find anything wrong with the collet other than it would not close down far enough.
Gail in NM


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## djc (Feb 4, 2011)

As others have said, have a good look at the collet. Make sure there's no dross in the slits. An ultrasonic cleaner is handy for this.

Also, have a look at Rego-Fix's site (they invented ER collets). Somewhere on there is the recommended torque for the nuts: it is surprisingly high.


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