Rotary Table Drawbar

I have a small rotary table with an MT2 hole in the centre. I want to put my MT2 ER25 Collet chuck in to machine some concentric lands at 90 degree spacings on a small (12mm diameter) part.

The problem is that the bottom of the central tube is only about 3.5 mm above the base of the table itself - so not enough room for an M10 bolt and washer to act as a drawbar. It's not a problem with the table set vertical, but horizontally it's a bit of a problem.

I am planning to make up a special which is thin enough on the bottom to fit, and with holes for a pin wrench to do it up.

However, given that the real grip on a morse tape is provided by the taper itself once engaged, could I get away with installing the collet holder. Use a standard M10 bolt and washer to pull the taper up fairly tight, then remove the bolt before mounting the table horizontally?

Or is that pushing my luck!

Or alternatively, am I missing something.

Edited By Peter Cook 6 on 29/05/2021 19:11:30

You could mount the table on parallels or a ground block with a hole in it to allow room for the drawbar projecting. I would play safe and use some form of drawbar. A 3mm thick head for your special drawbar would be plenty strong enough should you make one.

Edited By old mart on 29/05/2021 19:16:33

Edited By old mart on 29/05/2021 19:19:34

You may get away with a M10 CSK cap head screw, should bear on the edge of the 15-16mm hole and only project a little beyond that.

Hi,

Sometimes i use modified caphead screws to enable a a low
profile type of fixing , this may work in the application in
securing your chuck as a draw bolt .
A 10 mm caphead screw is turned with a 10 deg taper
and the washer made after so the head of the screw
is level with the washer ,is a simple job to do and has a
8 mm allen key.

John

Can you show/explain why mounting the RT vertically would not work?

Edited By not done it yet on 29/05/2021 21:24:05

The drawbar on my RT is a standard hex bolt with the head turned down (on the threaded side) to accept a flat washer. The thread size is M10 and washer is for M12. (A 2 minute machining job).

Paul.

What needs explaining " It's not a problem with the table set vertical.............................."

Yes, but why not just carry out the job with the table in the vertical position? If that is no problem, why engineer a problem by trying to do it a more difficult fashion? KISS Principle operates in my workshop - even though I don’t always do things in the correct order of best fashion.

Without seeing the part it's hard to say if it could be done either way and I assume the OP is also thinking of future uses.

Without seeing the part - or it being explained precisely - is why I asked the question in the first place.🙂 I don’t like assuming. Too often wrong. Better to stick to the thread details as provided by the OP. Future projects/uses might have different requirements anyway. Like I said, KISS principle suffices for most situations.

.

Sorry, ndiy ... but I think the Simple thing would be to respect Peter’s opening statement:

”I have a small rotary table with an MT2 hole in the centre. I want to put my MT2 ER25 Collet chuck in to machine some concentric lands at 90 degree spacings on a small (12mm diameter) part.”

and just answer the question that follows it.

MichaelG.

.

No, I can’t deduce exactly what the part looks like ... but I think he deserves sufficient respect for us to believe that he has good reasons to want to machine it the way he does.

Thanks for all the help as usual - helped provide a solution to the problem and made me think a bit harder!

M10 is a VERY big size for the things I do, and I only had a stock of M10 cap heads. It (should have but) did not occur to me that an M10 CSK would have a head wide enough to cope. So step one is to get a few M10 CSK bolts of the relevant length (Amazon prime is wonderful - arriving today - and cheaper than the petrol to drive to my nearest hardware store).

I would/may copy Paul's idea at some point - once I acquire a M10 Hex bolt, or simply make a thin washer with a centre hole that matches the csk bolt. - Thanks for the idea.

The idea of lifting the table on parallels is not one I had thought of - stored for future reference, however the daylight over the table on my SX1LP is fairly limited as it is, and fixing the drawbar issue will give me future proofing. A ground block is way more complex than I could make with sufficient accuracy.

To answer the queries, the part is one half of a small dog clutch. Overall diameter 12mm.

I had planned to cut the lands out using three cuts. A & B use a 2mm cutter. C is a 1mm cutter. I was planning to do cut A - rotate 90 - repeat four times, then do cut B and rotate four times again. Then rotate 45 degrees and do cut C - probably going straight across, rotate 90 and repeat.

I could do it by holding the part in a Stephenson block in the vice, but given my propensity for error (and scrap production), setting up all the cuts differently seemed somewhat risky. Rotating the block would (probably) loose centre at some point - see above propensity!

I could see how to do cuts A & B it with the table vertical by doing A & B from opposite sides, but I can't do C that way ( I don't think).

Thanks again for the help and ideas. Just waiting for Amazon now.

Edited By Peter Cook 6 on 30/05/2021 12:22:02

Edited By Peter Cook 6 on 30/05/2021 12:26:46

I sometimes stack my RT on a pair of 123 blocks - it only has 2 clamping points when in horizontal mode.

If I had to make that with a vertical only Index I think cuts A and B in the mill, then slot C with a hacksaw as a hand operation.

Dave

Edited By Dave S on 30/05/2021 12:46:28

Update. Amazon delivered.

One M10 35mm CSK bolt is perfect.

Thanks again for all the help.

.

I was out for my walk today, and found this lying in the road:

.

it is in one piece, has a Torx socket, and appears to be self-tapping ... but, in general concept is uncannily similar to your design.

... Looks useful : Does anyone know what these are called ?

MichaelG.

Hi Michael,

Tyre fitters bonus.

John

Looks like a rusty self piercing setscrew!

Intended to be driven in by an air gun or a battery electric screwdriver.

Probably fell off a passing car.

Howard

.

I doubt if I will locate any with that description, Howard ... but thanks anyway !

MichaelG.