5C clamping range.?

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As the title says really.

I know that ER collets have a bigger range to 5C ones. But there has to be some latitude. What is it.?

Cheers, Nick

A few thou.

The problem is as they are only split at the front they may close down onto smaller dia work but it will wobble about as the far end of the work is loose in the nominal bore of the collet.

Edited By JasonB on 20/07/2015 10:06:35

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Cheers Jason.

So more for a production environment than a model engineers workshop.?

Nice to have but a bit limiting. Or am I missing something.?

Pity ER's don't do square ones.

Thanks, Nick

Nick, if you look at the steps between 5c collets 1/64" seems the be the norm, with 5C collets you can go undersize with the item to clamp but should never force an oversize item into any collet as it ruins them. I find the clamping range useful on ER collets but object to the amount of clamping force needed, a ball bearing nut is supposed to help but I have yet to try one. Clamping force on 5c is much lower but you are limited in range. I suppose it depends on what you have and what comes your way. The closer or collet chuck has to be of high quality otherwise you won' t get the accuracy, if you buy a used 5c collet or a cheapie and it under performs it will be obvious against other known good collets you have, wheras if the chuck is out....

It is quite possible to hold square material in an ER collet but it's preferable to do so in a split fixture of some kind.

Let's say you want to hold something that is 8mm across the diagonals - then turn a brass piece to a clean (say) 12mm diameter (I have a good quantity of 1/2" material I use for this) and then holding it in a 12mm ER collet - drill the brass to 8mm (or whatever the diagonal is). Remove the fixture and cut a slot right through the length and then two further slots at 120 degrees - but not right through. When tightened in the collet this fixture will hold your square material quite firmly enough for most operations.

The (more time consuming) alternative is to machine two pieces of mild steel (or brass) with slots which are as wide as the material and half the material size in depth. Then using a very carefully centred mandrel made of the square (or rectangular) material - turn the two pieces between centres to a convenient diameter for your ER collet. This will obviously provide a firm grip on the material, preventing any turning movement, should you really need it. However, the first method is generally simpler and will be sufficient for most purposes.

Of course, for most 'one-off' operations, a four jaw is the simplest solution.

Regards,

IanT

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Closely approximating zero

MichaelG.

Well Nick I and many model engineers seem to find a use for 5C in the workshop. The range is not zero otherwise you would be stuck with holding silver steel or precision ground rod. They will hold bright mild steel which is usually a thou or two under size quite adequately.

And if you really want to be able to hold anything Hardinge will do them in 0.001" increments in their super decimal range.

What I do if the 5C chuck is mounted and I want to hold an odd size is just slip in the 5C to ER32 adaptor, Tony with a bearing nut I can often just use my hand to get enough grip if the part is not too much below the collet size and its just gental turning, threading needs the spanner to tighten.

The 5C is nice as you only need a chuck key to tighten which leaves one hand free, changing collets its about teh same time for both 5C and ER.

If you want Nick to hold square sections using collets you may find my method of adapting round collets worth considering. Have a look here **LINK** I have used it down to 2mm square, in fact it was that requirement (making about 100 square nuts for a model cart) that made me come up with the idea.

Harold

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Jason,

Bearing in mind Nick's 'benchmark' ER .. I think that confirms that the latitude is 'closely approximating zero'.

MichaelG.