Soba rotary table

[Neil LawtonParticipant @neillawton69170]

I recently received a Soba HV6 rotary table and found the following:
(i) With the worm gear disengaged, I can push/pull the table laterally (orthogonal to the axis of rotation) by about .05mm. Tightening the axial preload collar on the base of the unit has no effect on this 'slop'.
(ii) The worm ring gear appears to be slightly offset from the axis because cranking the handwheel stiffens for one half of the rotation and loosens for the other half. This means that I can set backlash to 2' on the tight half but it goes out to 8' on the loose half.

This is my first rotary table so I have nothing to compare it with. Would the group consider this acceptable or is it enough to return.
Thanks.

[Neil LawtonParticipant @neillawton69170]

[Michael GilliganParticipant @michaelgilligan61133]

Well, Neil … I wouldn't want it.

But: How was it advertised ? [i.e. is there a specification that you can challenge ?]

As the late John Stevenson used to say: Such things are often "fit for purse" and their "fitness for purpose" needs to assessed in that context.

Note: Very good Rotary Tables can be very expensive.

MichaelG.

[John HaineParticipant @johnhaine32865]

Clearly crap. Send it back.

[JasonBModerator @jasonb]

Having had first hand experience of using one of these Soba rotary tables for about the last eight years I can't say I have ever felt the need to take that measurement until I read this post. I have not noticed an issue with mine and it does what I would expect and I have made models using it that have taken medals and highly commended awards so to me it's certainly fit for the purpose of making models, others may have other purposes that require more.

I have about 10' backlash on the handwheel which is a nice round number when you need to compensate for it.

J

[Chris TriceParticipant @christrice43267]

I have both a Vertex 4" and Vertex 6" Rotary table and although the 6" tightens slightly as you turn the handle for half a turn, it remains smooth and there's no appreciable slop in the mechanism and I like them both. Based on this, I bought (the company paid for it) a (cheaper) Soba 6" rotary table for use at work which, because it looked identical to the Vertex, I mistakenly assumed was made on the same production line and simply rebadged. By comparison and based on expectation, the Soba was disappointing being rougher finished and not as well made. However it worked sufficiently well for the stuff we were chonking out. It made me cautious about buying another though having been spoilt by the Vertex, so unless you're on a tight budget, I personally would say pay the extra if you want to be sure.

[Neil WyattModerator @neilwyatt]

The actual backlash is less important than the angular accuracy, so I'd test that rather than the backlash.

The spindle should be somewhere around a slide fit, which means some movement. Assuming the spindle is about 1 1/2" diameter that would be somewhere around 0.025mm, tighter than that would be a push fit and it would be likely to jam or pickup when rotated being a plain bearing.

It might be worth checking that the spindle is well greased, this may help the 'feel'.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 10/03/2019 12:28:15:

The actual backlash is less important than the angular accuracy, so I'd test that rather than the backlash.

.

Let's assume that Neil Lawton does not have access to optical polygons etc.

How does a hobbyist test angular accuracy ?

I offer a suggestion that I have made before, and invite others to improve upon it:

1. Make two plates, each with a central hole to closely fit a central spigot in the table
2. Mount them [pinned together, with a sacrificial plate below] securely on the table.
3. Using the table to the best of your ability, drill and ream [or use a slot-drill] seven holes on a pitch circle
4. Remove and separate the plates
5. Insert closely fitting pins through all eight test holes [central, plus seven]
6. Remove all but the central pin, and step one plate around by one hole
7. Re-fit the seven pins [if you can]
8. Repeat 5,6,7 until all seven positions have been checked
9. Invert one plate and repeat 5,6,7,8

If all this works to your satisfaction, the angular accuracy is 'good enough'

If it proves impossible to insert any pin through both plates, then test with smaller pins to quantify the error.

MichaelG.

[Neil WyattModerator @neilwyatt]

Or stick a laser pointer on the table and aim it perpendicular to a far wall.

Requires a bit of trig and care in setting up….

[Paul KempParticipant @paulkemp46892]

Or… Just accept it for what it is, a cheaply made bit of kit to provide an economical solution to the masses with a standard of accuracy commensurate with its cost. OP didn't state why he had bought it and what it's intended use is. If it's for the usual back yard engineering jobs like steam engines then bolt it on your machine and get using it. If it's for instrument making which requires extreme precision and formal calibration of the final product make sure your shop is kept at 20 degrees at all times, your measurement tools are only of the highest quality properly calibrated and buy a decent one. What else can be said? Seem to be a lot of people here chasing elusive microns where a couple of thou or in some cases 1/64" is perfectly adequate. Life and hence time allotted to us is finite so spend it getting on with the project and not chasing accuracy you don't really need! If you do need it don't buy your kit from purveyors of leisure grade equipment.

Paul.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 10/03/2019 15:46:04:

Or stick a laser pointer on the table and aim it perpendicular to a far wall.

Requires a bit of trig and care in setting up….

.

Do you propose a straight wall, suitably 'trammed'

or a truly circular wall, concentric with the table's axis of rotation ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Paul Kemp on 10/03/2019 16:10:46:

Or… Just accept it for what it is, a cheaply made bit of kit to provide an economical solution to the masses with a standard of accuracy commensurate with its cost.

Pretty much what I said in my first response.

MichaelG.

[Kevin DParticipant @kevind]

I purchased 6" soba table some years ago from a well known UK supplier. It failed and needed a new worm wheel. I was advised that part HVRT-03 was not available. A supplier here in Australia had a table that looked the same and could get a gear for $98 AU. Now the good news. They had a sale on the next week and a 6" vertex was $180. The soba dividing plates and tail stock will fit it.

The reason for the failure was having too much or any back lash while milling 16mm cooling channels in a 300dia Al plate. The worm gear is soft cast iron spur gear cut at about 1.5 degree helix angle (not a worm wheel). It had teeth missing in more than one place around it. Now the fix. A small amount of grinding with a burr to clean up any high spots in the table body and a spacer to go between the table top and the gear. The gear now hangs lower just clearing the inside and the worm bears higher up on an undamaged part of the gear. It now work fine.

Any heavy load on these gears will cause damage.

[Dave HalfordParticipant @davehalford22513]

So these are tables that you don't use for milling curves

[HopperParticipant @hopper]

Posted by Kevin D on 12/03/2019 11:42:55:

…The worm gear is soft cast iron spur gear cut at about 1.5 degree helix angle (not a worm wheel). …

There-in lies the rub. As such there will be point contact only between worm and gear. Suitable For Positioning Only and not driving under load. Pity they don't mention this in the instructions as there have been quite a few others posting similar experiences. If you know, you can drill holes around the periphery of the table and use a tommy bar to provide rotary motion during machining by "hand feed". Stops clamped around the periphery provide control over total angle machined. Just like the simple wormless rotary tables designed years ago by GH Thomas and Harold Hall.

[JasonBModerator @jasonb]

Posted by Dave Halford on 12/03/2019 11:49:18:

So these are tables that you don't use for milling curves

Perfectly suitable for curves, it's just overloaded with work that is probably too big for them or take excessive cuts they will fail, much the same for any tooling.

[Neil WyattModerator @neilwyatt]

Posted by Michael Gilligan on 10/03/2019 16:11:02:

Posted by Neil Wyatt on 10/03/2019 15:46:04:

Or stick a laser pointer on the table and aim it perpendicular to a far wall.

Requires a bit of trig and care in setting up….

.

Do you propose a straight wall, suitably 'trammed'

or a truly circular wall, concentric with the table's axis of rotation ?

MichaelG.

A straight wall and a little care will be fine – but you already know that

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 12/03/2019 12:24:52:

Posted by Dave Halford on 12/03/2019 11:49:18:

So these are tables that you don't use for milling curves

Perfectly suitable for curves, it's just overloaded with work that is probably too big for them or take excessive cuts they will fail, much the same for any tooling.

For heavy curve cutting a £150 6" rotary table might be considered disposable. You can pay three or four times more dosh for a better version of the same table, but it's still lightly built for hacking out curves, and much more painful if you destroy one!

It's like the mitre saw I bought for a one-off woodworking job. Much cheaper than a professional saw and slightly cheaper than hiring a professional machine. It cut the 40 odd joints I needed and it's still working. For what I needed it was fit for purpose and value for money. When the saw breaks I shall replace it. John Maynard Keynes famous last words were 'I should have drunk more champagne'. In that spirit, I'm not keen on spending a fortune on tools that will be in perfect condition when I'm in a graveyard…

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 12/03/2019 13:15:29:

A straight wall and a little care will be fine – but you already know that

.

Quite a lot of care [and some deviousness] if you want to test the full rotation.

MichaelG.

[John HinkleyParticipant @johnhinkley26699]

Not Soba, but an interesting watch if you have 90 minutes to spare…. Stefan Gotteswinter strips and reworks a Vertex rotary table to move accurately and smoothly to correct similar problems to those experienced by the OP, at :

Improving a Vertex HV6 rotary table

John

[VicParticipant @vic]

As a matter of interest, Vertex are based in Taiwan and rightly or wrongly Taiwanese stuff is reckoned by some to be superior to Chinese products. Vertex do though have a good reputation. Soba (Shoba) are I believe made in India.

[Bill PhinnParticipant @billphinn90025]

Posted by Vic on 12/03/2019 15:51:30:

As a matter of interest, Vertex are based in Taiwan and rightly or wrongly Taiwanese stuff is reckoned by some to be superior to Chinese products.

I'd say the generalisation is justified, Vic.

The manufacturing environment in the two regions is fundamentally different. Probably the most elusive yet important factor is the political situation in each region, and the degree to which this allows fair competition (healthy for innovation and quality assurance) in private enterprise to prevail.

Going back to Soba, I've got a three inch rotary table of theirs that I bought ten years ago, and it's been fine for what I've wanted to do with it. Maybe Soba's manufacturing standards were better ten years ago or maybe I'm just not a sophisticated enough user (yet) to have discovered its limitations..

[Ketan SwaliParticipant @ketanswali79440]

Neil L,

Welcome to the forum. By now you have many responses to consider. It would be great if you could share your thoughts on what has been posted so far.

As has been suggested, there are several qualities linked to price and purpose of use. As a trader/importer (ARC), I have been interested in this particular subject and I have been following the development of the brands mentioned for rotary tables, for over a decade. I would like to add a little clarity to some of the points raised:

Indian – Soba – used to sub-contract to one place for a long time. About 8 months to a year ago, they moved the manufacturing to another place. Most of the other Indian suppliers/exporters purchase from one particular maker, mainly due to price. The quality is based on Q.C. post manufacture, by the seller – (not the manufacturer). Depending on the seller, the rejection rate at source (at Exporters workshop pre-export) is variable.

Vertex – Taiwan – at one time, their HV6 was made in Mainland China by a particular manufacturer (factory A) which has a great 'technical' reputation and consistency. However, to the best of my knowledge, Vertex moved away from them around five years ago, mainly due to price. Since then there are only rumours about which factory they now subcontract to. One factory told me that they buy semi-finished from them and then finish off in Taiwan. I am un-sure if this is true.

Then, there are two more factories in Mainland China – factory B & C, cheaper than factory A. Below is my current understanding of quality vs. price:

China factory A: Highest quality and highest price.

Vertex : Quality 'maybe' similar to or marginally higher than China factory B & C, and price close to factory A.

China Factory B & C: Quality definitely not as good as factory A, but close or similar to Vertex, but price nearly 50% of factory A, and definitely cheaper than Vertex.

Soba : Quality/consistency uncertain at present, definitely not the same as Chinese factory A, and maybe close to Chinese factory B & C, but still I am not 100% sure . Price 'probably' 60% cheaper than Chinese factory A.

Rest Indian exports mainly from one Indian manufacturer: based on QC, quality close to or equal to Soba. Price 70% cheaper than China factory A.

I have been 'pondering' this subject of rotary tables since 2004. Although I know about the quality and the pricing from these makers over this time, I have found it difficult to making a decision about what to add to our range, from the above qualities/makers (excluding Vertex or Soba). If this decision was just based on quality, I would add China factory A product to my range without a second thought. But their price is nearly 3 x higher than the lowest – Indian, and nearly 2 x higher than the other Chinese offering.

Ketan at ARC.

[Ketan SwaliParticipant @ketanswali79440]

Posted by Bill Phinn on 12/03/2019 17:40:12:

Going back to Soba, I've got a three inch rotary table of theirs that I bought ten years ago, and it's been fine for what I've wanted to do with it. Maybe Soba's manufacturing standards were better ten years ago or maybe I'm just not a sophisticated enough user (yet) to have discovered its limitations..

Ten years ago, the sub-contractor Soba was using was still considered to be 'new' at making such tables. The QC took place in Sobas' warehouse. What happened to the rejected stuff in old days is different to what happens to it now.

Nowadays, a good percentage of the reject ends up on eBay by kids traders who buy two and three pieces at a time from the manufacturer. These kids traders don't know the first thing about the stuff they sell.! However, reading their feedback posted on eBay, the posts are variable from excellent through to negative.

As mentioned earlier, Soba moved away from the sub-contractor it used to use earlier. Soba has a good working relationship with Chronos and some others. ARC works with a limited number of Indian manufacturers other than SOBA. For rotary tables, ARC has yet to make a decision for sourcing these type of rotary tables be they from India or Mainland China.

Ketan at ARC.

[JasonBModerator @jasonb]

At about 56seconds into that linked video he sums it up quite well

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