4 in rotary table

I purchased a 4" rotary table a couple of years ago from a supplier attending the Midlands show, didn't use it much until this week. Now had a problem with 4 hole centres drilled on it at 90 deg between each, didn't line up with holes in a marked out plate, checked that and plate was OK. Now checked the 2mt centre hole in the RT using DTI and its out of centre by almost 10thou when the table is rotated by the driving handle. Question is, is this adjustable out, if yes how? or is it normal with these foreign mfg tools. Would trying to average out the difference be the only way the RT can be used with useable accuracy?Anyone have any ideas?

Cheers

GW

'Usable accuracy' is something only you can decide.

I doubt very much whether the MT2 bore can be moved or adjusted relative to the table's main bearing. Its not that unusual though to have to carry out some rework to make (any) product to perform as you want. Bear in mind that you can only make it perform 'as it should' if the item was provided with a specification in the first place.

The first thing to check is how close fitting the table is in its journal, if its OK then I would forger the taper bore and machine it to parallel bore. If you do this on your milling machine with an end mill (say 10mm diameter) using something like a battery drill to rotate the table in it own bore, your new bore will be as concentric with the table as it will ever be.

Ian P

10 thou does sound like a lot. Under normal circumstances it would be best to return it for a replacement or refund. I realise that's difficult given how long ago you bought it but may still be worth a try. Failing that Ian's idea may be worth a try provided it's not hardened. Good luck, let us know how you get on.

For what its worth, I agree with Vic.

Thanks

Trevor

Edited By Toolgrinding on 28/09/2014 11:16:14

Forgot to ask Graham, what make of RT is it?

I too had a similar problem with a RT purchased from one of the well known suppliers. Fortunately, always the careful one, I checked it ASAP and found the MT insert was not that accurate, swapped out by supplier.

With a little patience in setting up for the MT angle, you should be able to make a replacement that is more accurate than 0.010". In my own case, it was not only out radially, but the axis was out of true as well

I hope your table has an insert that can be changed.

Thanks Ian, Vic, Toolgrinding and Kwil for the replies. Believe It was purchased from a machine tool supplier south of Watford, it's a HV4 RT/DH, used it only for machining 'non important' radii on up to now so didn't notice the lack of accuracy, must be at least 3 years old as I haven't been to the Midlands show the last twice it's been held. There's no insert with it, it's bored 2MT direct into the table, wanted that as you could use a 2MT threaded Myford adapter and put the chuck straight onto it from the lathe. (checked the adapter in the lathe and that's running true). The table's not hardened so it can be re-machined, think I'll go Ian's route and bore it parallel then make a close fitting Myford threaded adapter to suit so chuck can be moved as required. Will see how it goes.

Cheers

GW

Just an update. From the pictures across the web the maker looks like Soba. Can see that Arc do parallel sided adapters with 2mt bore so might try that before turning a threaded one. Like to use Arc where I can.

Cheers

GW

These are the specs for the Vertex 4" Rotab, let's hope it's in spec when I get one later in the year!