The Home Machinist!

If i already have ER collets in english (1/32) sizes. is there any reason that i should need metric collets for metric size parts. would i do alright with a 16 mm part in a 5/8" collet or should I use a 21/32 collet. OR get a metric one.

The ER are dual angle and compressible over a wider range. 16mm requires more compression. If it freakin works, do it. Blame me later but there is a certain time when you're all set to get it done. Dual compression is great but the grip would be in the center, not uniform and don't let it slip.

The ER collet ranges don't have gaps in capacity so in theory you don't need metric and imperial, I have metric only and haven't needed any Imperial ones to hold Imperial tooling,

- Nick

In theory, yes. But ER collets are increasingly unpleasant the further you are below nominal. So I bought a fractional set. For many/most shanks (or material) I may choose to grip, it only requires a minimal amount of tightening to grip. But if you cross match sets, you'll find some sizes require quite a bit of cranking to grip, and almost none are conveniently close on size.

I defer to Russ.

One should not forget a couple things. One is that a collet is sized for a given diameter. To grip above or below that diameter requires that the fixed portion of the collet to flex, which, in my mind, can be beyond reason. The other thing to consider is that collets are not soft. They are heat treated, which implies that they are not fond of being deformed. If deformation persists, one can expect failure. Failure of the collet means it must be replaced.
The AR series is broadly reputed to be able to grip a multitude of sizes. For the reasons I stated above, I don't agree.

Will they do as advertised?

Yep! They do.

But should one use them that way?

I don't.

Harold

I've been using an ER 40 set for over 10 years and haven't had any break, distort or otherwise "take a set".
I assume that the level of distortion is within the elastic range of the material used - in decent sets anyway

- Nick

Magicniner wrote:I've been using an ER 40 set for over 10 years and haven't had any break, distort or otherwise "take a set".
I assume that the level of distortion is within the elastic range of the material used - in decent sets anyway

- Nick

Thanks for the report. Helps those (like me) who may be somewhat skeptical.

Harold

Since the subject has come up, I'm wanting to sort out things ER and decide what to buy. Or more specifically, who to buy from.
I've read some things that indicate that some products sold as "ER" aren't compatible with the 'standard' ER. Obviously I don't
need any non-standard ER. I think I remember some comment about a Shars product that was being sold as ER but someone
found the collets or nut or ??? didn't interchange with the standard. But it may have been another supplier.

And what about this business of the nut 'snapping on' some types but not others? Should I have a nut for each collet?

Anyway, need MT2 shank, 3/8-16 drawbar and 5/8" collet max. And a low price. I don't care if it's an import as long as
the quality is fairly decent.

Can anyone make a recommendation or two??

Thanks,
Pete

Unlike a 5C collet, the ER collets close down at both ends, so they will not suffer the problem of gripping at one end or the other when the workpiece is under- or over-sized.

What will happen with ER collets when you are gripping undersize parts is that the grip will not be full circle. Think of turning soft jaws for one diameter and then using it on a smaller diameter - it will grip in the center, but it will grip the full length front to back.

Steve

Harold_V wrote:

Magicniner wrote:I've been using an ER 40 set for over 10 years and haven't had any break, distort or otherwise "take a set".
I assume that the level of distortion is within the elastic range of the material used - in decent sets anyway

- Nick

Thanks for the report. Helps those (like me) who may be somewhat skeptical.

Harold

Think of them as the opposite of the K.O. Lee expanding grinding mandrels.

They have a huge range in comparison, and their job is to expand and contract over that range.

Since you have a 1/32” size collet set, the answer to your question is no you don’t need a metric set to cover gaps. There are no gaps in a 1/32” set like there are in a 1/16” set.
For your 16mm part:
16mm = 0.630”
A 21/32” er collet has a gripping range of 0.617-0.656”.
A 5/8” collet has a gripping range of 0.586-0.625”.
Use the 21/32” collet for a 16mm part. No need to stretch the 5/8” collet.

Tom