6" Vertex rotary table problem

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I have a 6" rotary table which I use occasionally.
I have a real problem accurately getting the position of the centre of rotation. The MT2 centre on the table is not actually the centre of rotation. With a gauge on the inside of the taper the eccentric error is around 6 thou.

So can the MT2 taper be fixed with limited equipment ? (Mill, lathe etc) or
is there an easy way to set it up without using the MT2 centre taper? If so I can use it instead.

Best Regards

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[WeldingRod]

You can use an edge finder on the rim.

You could also cut a small step around the MT hole using an end mill and rotating the table to ensure it's TRUE to the axis.

Sent from my SM-G892A using Tapatalk

[picclock]

@WeldingRod
Thanks for the reply. I think that the step-method will be best. I could then turn up some discs on the lathe with protruding centres which will align the parts to be machined. Certainly that should work for now.

Longer term I hoped to use an MT32 chuck to hold some parts but 6thou is just too much error. I suppose the only real fix (when I get round tuit) is to take it apart and machine/regrind the taper - toolpost grinder design anyone ?.. . been meaning to make one of those for ages .. .

Best Regards

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[WeldingRod]

It would be utter insanity, but you could shim the table at the Morse angle and bore it while rotating...
I did mention insanity ;-)
Probably better to take it apart and use a lathe on it.

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[hanermo]

Mount it on the mill, with the 7/x MT2 taper as tilt, with a grinding stone as the tool in mill.
Itīs how jig grinders work.

You are only taking off a few grams of metal.

I would expect any half decent effort to get around 0.01 mm TIR.

[awemawson]

It'll work, but your MT3 centre will end up a surprisingly large amount lower - funny things taper fits 

[BillTodd]

 As mentioned above, mount indicator on the table and clock the spindle of the machine.

One thought, I wonder if the table is bolted to the bearing?  even my sip has a bolted construction so might be worth checking.

[picclock]

@WeldingRod, hanermo
Thats a neat idea I hadn't thought of. I will give it a go as its no good as is.

@BillTodd
This table has about 40 turns for one revolution, not sure my wrist could take it 
I have an adapter for a dti which clamps directly onto the er32 collet nut. This is what I usually use. Originally lined it up using the morse taper and couldn't figure out why the bits were so wonky.
This table is a one piece casting with plain bearing and taper all in one.

@awemawson
If I get it right it will increase the depth by 230thou - but I can live with that

Best Regards

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[BillTodd]

Normally, one would disconnect the worm and rotate table manually..

interesting that it has only 40 turns per rev, presumably 8t has an indexing facility??

Bill

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@BillTodd
The number of turns for 360 degrees is 90 and the indexing on the wheel is for 4 degrees - I just new it was a lot of turns. The reason I don't disengage the worm when setting up is that its nigh impossible to get my fingers to the locking screw. This is because I have a large fixture plate attached to the top of the table - its a bit of a nuisance because I always bang my knuckles against it when rotating the table.

I have machined a step as suggested by WeldingRod, and that used in conjunction with my er32 collet clamp dti makes it easy to set up.

I've getting closer to finishing my larger CNC mill, and then with luck I will be able to repurpose the rotary table as a 4th axis for gear making etc.

Best Regards

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[Bluechip]

No idea if this is relevant to this thread or not but I have a 6" 4-slot Vertex RT.
Made in Taiwan, had it for about 20 yrs.
The 2MT socket presses out on mine.Could the  removed socket then be set up in a 4-jaw and bored ?
Or have I got this ALL wrong again. Has been known. 
Dave

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@ Bluechip
I hope it is, but I have yet to disassemble the table. Looking at the underneath it appears to all be in 1 piece. I had also thought of boring it out parallel and fitting an MT2 socket which I have in my parts box, think it might have been part of an adapter. But, I'm not sure how much meat will be left on the table if I do that.

Best Regards

picclock