Rotary Table Quest

Hi

I am looking for a Soba 6" rotary table and a chuck adapter plate. Everywhere seem to be out of stock. Does anyone have a secret source or can offer advise on a suitable alternate that is in stock?

Cheers

I'd look for second hand, sadly there are loads of engineering companies out there selling off top quality equipment at knock down prices. I don't have a Soba rotary table but their products are, in my opinion at best average. Good luck with your quest though.

One hit from goog le.

**LINK**

They seem to have plenty to add to the basket?

If they don’t have the size you want they are likely to be restocking shortly.

Edited By not done it yet on 21/11/2020 11:02:28

Buy a Vertex - just compare the differences in the engraving never mind the internals.

If you can afford the Vertex, it is made to a higher standard than Soba. I have a 6" Soba, bought privately, but in new condition, and the first thing I had to do was ditch the central needle roller bearing and turn up an aluminium bush. This was because I noticed a large ammount of radial play when the table was unlocked. I did not think 0.010" movement was reasonable, and who needs a needle roller bearing for the speeds at which a rotary table achieves. Now it works ok. As the table has four tee slots, a four jaw independent with front mounting is easy to fit. I have drilled and tapped holes for a 5" front mount Pratt Burnerd three jaw scroll chuck. This requires some thought, I made the mistake of drilling one of the holes into the drilling for lubrication, and had to re align all three. Now the holes are in the right place, fitting the chuck is easy, and with a test bar in the central Morse taper, and the chuck jaws lightly clamped on it before the screws are tightened, the chuck is centralised to about 0.002" tir which is good enough for my purposes. Having some short grub screws to put in the holes when the chuck is not fitted keeps the muck out of the works.

Having had more bad than good Soba products, I avoid them now.

Another vote for Vertex, though - not had a bad Vertex product yet, though prices seem to have gone up a lot since I bought my 6" RT.

Nigel B.

ps. I note that RDG Tools show a 6" "no brand" 3 tee slot rotary table here  Apart from the 3 rather than 4 tee slots, it looks superficially like my Vertex unit.

Edited By mgnbuk on 21/11/2020 17:18:16

Vertex at Rotagrip;

Vertex 6"/150mm Horizontal/Vertical Rotary..

I have a Vertex, and like it..

I have two Vertex 6” RTs - the earlier, better quality, of Taiwanese manufacture. One has 3 slots, the other has 4. I prefer the 4 slotted version.

Normally, the set of dividing plates is extra, I have three, but they don't work for every number, I was unlucky when we wanted 118. Degrees and minutes had to be used for that job. The last job I did was 7, and it was easier to just use the nearest degrees and minutes.

Edited By old mart on 21/11/2020 19:37:54

I have a Vertex, and think (but cannot prove ) that the quality is better. A set of Division plates and a tailstock are valuable extras to have, Invaluable if you intend to use it for gear cutting.

The HV6 is a 90:1 ratio which allows more precise positioning than tables with 72 or 36:1 ratios.

The central bore is 2 MT so there are 2 MT adaptors to take a Myford fitting chuck.

If you do go for a Vertex, hopefully, the chart for the Divisions will have been amended to fix the errors. i.e. 13 divisions should be 6 turns and 36 holes on a 39 hole plate.

Don't ask how I know that!

Howard

Please could you expand on that remark.

What is the correlation between worm ratio and precision?

Doe it mean a 40:1 ratio is more or less precise than a 90:1? And what of a 4:1 ratio used by one of the big US milling machine makers?

Thanks.

I have a soba 4 inch the finish is good, the only downside is backlash, have tried to minimise it but it’s something I live with, nothing in life is perfect and for the money it was a good buy.
Dave W

If you think about it, divide an error by 36 or 72 and also by 90 which number is smaller?

4:1 gives you 90deg for each turn of the handle, would that be for a power feed to cut spirals?

EASY!

A fine thread produces greater resolution than a coarse one, otherwise Imperial Micrometers would use 10 tpi threads rather that 40 tpi.

On the assumption that the graduation lines are of equal width on both machines, an error in rotating the handwheel, of, just for the sake of argument, 1 degree will result in an error of 0.01111111 degrees in the table position.

With a 36:1 ratio, the one degree handwheel error results in 0.02777777 degrees in the table position...

So with a higher ratio, smaller positional error equals increased precision.

If a machine big, it is likely that the dials will be larger, possibly more closely divided (Room for say 0.25 graduations in place of single unit.

I would rather work with a 100 mm diameter dial than one of 25 mm diameter, for that reason.

I have a height micrometer, the graduated drum is large, so that the graduations are 0.0001" rather than the 0.001" on the thimble of a normal mic.

Equally possible that the big machines will have dials with a vernier, to improve resolution / precision..

Jig borers use precision length blocks and Dial gauges, rather than depending on leadscrews and handwheels ,for precise positioning..

Howard

A sip rotary table used in jig boring will have optical scales, but our scales are good enough for most jobs. The downside of a 90:1 worm ratio is the number of turns required to get anywhere. I prefer not to disengage the worm.

It is rather sidestepping the question to try to segue seemlessly from discussion of a RT with dividing plates to its use in angular indexing by means of a graduated handwheel.

If we do not throw away the dividing plates quite so casually, how does the worm ratio affect the precision?

I believe the Hardinge brothers, who made the 4:1 ratio device, knew a little of what they were doing.

I merely told what I know, and have experienced .

The question, apparently sidestepped was not of my making.

Presumably we can agree that a micrometer will provide a more precise form of measuremen than a six inch rule?

Thread drift?

The OP was looking to buy a 6" Rotary Table, and several of us suggested the Vertex HV6., which is 90:1.ratio.

Whether using the vernier scale , or Dividing Plates, both methods involve rotating the Handwheel.

Handwheel markings and Verniers or Division Plates are merely different forms of graduation. What matters in terms of precision is the error, or lack of it, in the position of the Table. So the higher ratio results in less error (greater precision ) in Table position for a given error in the input.

Now having started counting the angels on the pin head we can return to the original thread?

Howard

The 6" Soba can resolve 1 minute of angle with a 40:1 ratio which is good enough for government work. As for actually using the plates, I have forgotten how, so I would avoid them unless there is somebody around who knows and has a better memory.

The OP has had enough suggestions to make a decision based mainly on the budget available. Any of the tables will do the job ok for home use.

Edited By old mart on 21/11/2020 21:38:42

DC31K, If you want to cut an arc of say 60 deg you can't use the division plates so it comes down to the handwheel and as Howard says a 90:1 should give less error for his example of 1deg over or under rotation of the handwheel.

Old Mart, Soba tables are 90:1 not 40:1

Thinking back a while there was a thread where the various changes in sources of the Vertex R/Ts was discussed at length so all those with good ones how long have you had them?

My 6" Soba has done a lot of models in about the 12 years I've had it, does not get quite as much use now I also have the ARC one as there are a couple of features I like on that one of which is the 72:1. Though may be beyond budget

Thinking back a while there was a thread where the various changes in sources of the Vertex R/Ts was discussed at length so all those with good ones how long have you had them?

I doubt anyone would know re quality (good or not so good) - unless the RT is failing, or has has given operational problems.

Both mine were second hand (virtually as new) but were tagged with a “Made. In Taiwan” plate.🙂. One about 15 years ago and the other only a year or so.

I think modern RTs are generally OK for operations with the table locked, but not so good (shall we say) for milling while rotating the item.