Collet chuck for workholding on the mill

I thought this might be useful to someone. I needed to hold a small cylinder of brass to mill a transverse slot across one end - this is the top block of a new pendulum. But how to hold it for milling? I mounted the brass in a Myford collet in the MT2 chuck that screws on to the big bore spindle.

This is the chuck clamped down to the mill table with a silver steel rod to get the cross-hole aligned. But how to get the axis of the collet aligned with the spindle?

So I put 10mm collets in the mill and the chuck, and gripped a bit of 10mm ground steel in each before tightening the clamps.

Then zeroed the X and Y axes on the DRO. Now I could get the axes back in line using the table feeds. As always it took longer to work out what to do and set up the work than do the job.

That’s nice, John

... but it reminds me that I missed-out on some similar devices to hold Pultra 10mm collets

They had the locking at the base, of course.

RDG was selling them off a few years ago [reputedly they were specially made for British Aerospace]

MichaelG.

Unless I’m missing something I think I’d just use a collet block in my vice?

I too use a block in the vice (although not everyone has them) but I can see a big advantage with the JH method.

Accurately centering a block gripped in the vise can take time whereas allowing the job to self-centralise before tightening the clamps is near instant.

Ian P

No problem locating a block in the vice, just loosen the bolts/nuts and bring the pin on the spindle down, tighten collet and then nip up the vice fixings and zero DRO. This is why I don't generally use keys in my vice base. I use same method if I have a chuck on the rotary table .

Other advantage of the blocks is you can use it to do the cross hole first and a square block will keep things true for the slot at the end.

Had I possessed an 8mm collet for my ER40 collet block I could have used that, but I don't. Even then I have an alignment key (tenon?) in the chuck base, so probably easier to do it this way. I did use the block in the vice to hold the part for cross drilling before parting it off its 0.5 inch parent.

I think there is a big difference between large and small workpieces when using a self-alignnent technique.

Centralising (say) a 3mm diameter pin in a collet block already gripped in an unclamped heavy/bulky vice is not what I would call a sound method. I too dont use a key to locate the vice but once I clock it into position avoid moving it unless its absolutely essential. Since the DRO knows where the vice reference faces are it knows the position of the collet block axis (on the square block anyway, only one axis on the hex block).

Its debatable whether setting by DRO will be any better or worse than locating mechanically but I JH's method looks optimum for small components, just a pity that standard collet blocks dont have a deep groove at the 'bottom' end into which toe clamps could sit.

Ian P

Hi, well I did this about 4 years ago, with a piece of 40mm ram rod.

Much the same as John's idea, but I probably would use a collect block in a vice for smaller stuff, but hay! utilize what you have, that's what I say.

Regards Nick.

Edited By Nicholas Farr on 11/01/2021 15:56:45

It's always interesting to see another way of doing something which adds versatility to existing tooling.

I’d use a similar method to that already mentioned but instead of having to position two clamps I’d just tighten the vice. I often use this sort of method and ensure I have lots of “pins” in different diameters.

With the vice already clamped it’s just a matter of moving the table until the fixed jaw just touches the collet block then nip up the vice. It’s very quick.

There have been several methods mentioned in this thread so its not clear which one you are referring to, however when I put anything in a vice I just tighten it too

If the workpiece is already held on a pin in the mill spindle then its only safe to close the vice jaws if the vice is free to move, which is what the OP showed originally.

Ian P

Fully follow and understand what you are saying, I use the same technique often, however its determining the point of 'just touches' that introduces uncertainty of position, whereas clamping only in a downwards direction (whether vise or a block) minimises any error.

Ian P