Soba rotary table

[Anonymous]

Posted by John Pace on 15/03/2019 10:46:47:

As can be seen the thread form is asymmetric.

That's interesting; some of the internet pictures I looked at showed a highly asymmetric worm, also like a butress thread. Like a butress thread that would be good for power transmission in one direction; not so sure about accurate indexing in both directions?

Nevertheless it's a very impressive demo of hobbing.

Andrew

[Michael GilliganParticipant @michaelgilligan61133]

[ Jason ]

But at least they are a dirt cheap and easily replaced 'consumable'

… unlike the 47 tooth specials

MichaelG.

Edited By Michael Gilligan on 15/03/2019 11:37:53

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 15/03/2019 11:07:05:

I think the reason the rotary tables don't use the curved face of a typical worm wheel is that you would not be able to swing the worm out of mesh as easily as you can using the eccentric mount for the handwheel spindle.

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Just reading back over this thread, and realised that I had missed that comment, Jason

For what it's worth: My BCA has both a throated worm wheel and a worm that can be readily swung our of mesh.

… Might have something to do with it using 180 teeth on the periphery of the table.

MichaelG.

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Edit: These photos will save me the need to go out in the cold to photograph mine:

http://www.myford-lathes.com/milling_acc5.html

Edited By Michael Gilligan on 15/03/2019 14:37:32

[JasonBModerator @jasonb]

Ah but it looks like you swing the other way!

I assume two bolts are undone and it pivots horizontally about that small pin at the front.

The eccentric action found on the Soba, Vertex, ARC etc move the worm upwards and out which would not be possible if the wheel wrapped around the worm as per BCA.

[Anonymous]

My Elliott dividing head definitely uses a single enveloping worm wheel, and the worm disconnect is by way of an eccentric shaft. In contrast my "no name" rotary table uses a disconnect where the worm shaft has a single pivot. While it's a long time since I stripped down the rotary table I pretty sure it also uses a single enveloping worm wheel.

A worm and helical gear has point contact; a worm and single enveloping worm wheel has line contact. So less wear and tooth stress when reacting cutting loads.

Andrew

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 15/03/2019 15:22:18:

Ah but it looks like you swing the other way!

.

 … to whom ?

Edited By Michael Gilligan on 15/03/2019 16:18:01

[LathejackParticipant @lathejack]

I bought this 150mm Vertex Rotary Table new just over 15 years ago, the TOS chuck with mounting plate that I made is fitted most of the time.

This older version of the Vertex table has a hardened removable sleeve in the centre that is bored 2MT. The table also rotates in a radial needle roller bearing. The original factory fitted bearing shown was a German made item. It also has a needle roller thrust bearing under the base casting.

The radial needle roller bearing had to be replaced a few years after purchase because the factory applied grease had dried solid and jammed up the bearing. The outer race was forced to rotate in the housing of the base casting, it still ran smoothly and was only discovered when the table was stripped for a clean and lube up.

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…………….. My Rotary Table hand wheel tightens or binds a little through part of every revolution. This was found to be caused by the graduated collars front face being machined slightly out of square with its bore, the mounting bracket also has the same fault. If the two faces are very close or touching it causes the intermittent binding, which feels like a more serious internal fault with the meshing gears. Back the collar off a little and the table is superbly smooth. It may be worth checking this first if you have a table that binds in a similar manner.

Other than those two snags it is very well made and well with the £130-£150 it cost back then.

Edited By Lathejack on 15/03/2019 20:23:00

[Chris TriceParticipant @christrice43267]

That's the one I've got and your experience pretty much matches mine except in my case there was no hardened grease problem. It's a nice piece of kit well worth the money.

[Neil WyattModerator @neilwyatt]

It's also possible to use a curved worm with an enveloping wheel for maximum contact.

[geoff walker 1Participant @geoffwalker1]

Hi Neil

My table has the cylinderical worm enveloping gear, very nicely made, all 47 teeth!!!!

Geoff

[PeroParticipant @pero]

A little follow up on the 47 tooth issue.

I contacted RDG who responded quickly saying that they are contacting their supplier. I am waiting for the next response – I am assuming the weekend may have got in the way.

A slightly crude approach to the measurement of the worm height would suggest it is 18.5 mm plus or minus a tad ( one tad being equal to or less than 0.5 mm ).

This would mean that a NEMA14 would fit comfortably but given that loading would be light (mill with a high speed spindle driving small mills and drills ) I think I might opt in the first instance for a smaller NEMA11 to reduce weight.

Have yet to get into the workshop ( it's a fight ) to dismantle it and see whether it is worth the effort of motorizing it and to consider the motor mounting options.

After twiddling the little handle almost countless ( pun intended ) times to confirm that I too had 47 teeth I quickly became convinced that motorization is a necessity to prevent insanity, whether it is on this or an alternative small table!

Pero

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the update, Pero

I look forward to seeing some photos of its innards.

MichaelG.

[Ron LadenParticipant @ronladen17547]

Well it will be interesting to see how my Soba measures up as I have just ordered one, I have the little cheapie table but a better RT was on my future shopping list. I think a 6 inch version may be a bit big for my mill (SX2P) and was thinking that a 5 inch would be ideal and then found that Soba do a 5 inch.

I have gone for a set which has the RT, a dividing set, a tailstock and a 4 jaw chuck with mounting plate and its a very good price so I have brought it forward a bit.

Ron

[Paul KempParticipant @paulkemp46892]

Ron,

As I mentioned I think when you were looking for the first RT try and pick one where the locking / clamping arrangement pulls the table down on the base rather than with a screw that goes in on the side as if there is any play it will jack the table over when you lock it. Good move to get the tailstock too, always useful and a four jaw is a lot more versatile than a three jaw, you can overcome any inaccuracies in location of chuck to table by clocking the work in a four jaw, with a three jaw you are stuck with what you have and it doesn't take long to clock something true in a four jaw once you have had a little practice! Also a four jaw gives a better grip on round stock that a three jaw and allows irregular shaped work. So out of choice the 4 jaw is a lot more versatile if on a budget. You may well find though the standard plate set for the divisions you still don't have the numbers you need but worry not, you can make your own as long as you are not fussed about microns of a division!

Paul.

[PeroParticipant @pero]

An update on the RDG 2 3/4" rotary table.

I have received an email from RDG advising that their supplier would be sending me a ( checked [their advice] ) new table direct. A very good outcome.

Many thanks to Geoff Walker for pointing out the problem as mine was still in the original packaging and it may have been some time before I discovered the problem for myself.

Notwithstanding, I think I will still potter along with the motorising option as that tiny handle is a pain ( and I tend to lose count ).

I still haven't got to the dismantling yet but will attempt to send photos in due course.

Pero

[geoff walker 1Participant @geoffwalker1]

HI Pero,

New table, that's good news. Glad I was of help.

I've had mine nearly a year and have used it a lot.

It was only in the last month that I realised the main gear had 47 teeth.

If you remove the base it reveals the worm and gear arrangement and after several counts I finally accepted 47!!!!.

I'm looking to buy another larger one 4-5" diameter but this time will take advice first.

Geoff

[Ron LadenParticipant @ronladen17547]

The 5 inch Soba arrived so I gave it a check over whilst bearing in mind what Neil found on the 6 inch version.

Turning the table through 360 the handle felt very smooth with no tight spots though it did feel a bit light so I adjusted the gear mesh which is simple to do via a grub screw. Adjusted to get a bit more feel on the handle but with no tight spots, checked the backlash at that setting which is 0.001" so I am hardly going to worry about that.

I clocked the outside of the table through 360 and that is good to 0.0002", so running as near as damn it true. I then tried to find any float across the table using the mounted chuck for leverage but couldnt find any movement at all, the gauge maintained zero.

One turn of the handle is 4 degrees, I checked it at a number of settings and it is spot on.

So going by these checks I am obviously really pleased I couldnt ask for much better.

Down side..? there always has to be a downside, the 80mm 4 jaw is self centering not an independent but I,m sure it will have its uses. Also the chuck key with the 4 jaw needs a few thou of the key faces as it hardly enters the chuck.

[VicParticipant @vic]

Well that’s a result Ron, it proves you can get a bargain. In truth many of the cheaper tools are quite adequate for Hobbyist use.

[HopperParticipant @hopper]

Who was your supplier, Ron? And how much did it cost? Others in the market for a new rotary table may like to know. (And we know it doesn't have 47 teeth!)

[Ron LadenParticipant @ronladen17547]

Hi Hopper,

I got it from Chronos, it comes as a set £291.60 which includes VAT and shipping. The picture below shows the set….. 5 inch table, 80mm 4 jaw with mounting plate and external jaws, tailstock assy and dividing set. It suited my budget, I was thinking of saving for a decent table in the future but with tailstock and dividers added you are looking at over £700. Also would the table be better than the Soba, I dont know but from the checks I did this morning I very much doubt it.

Chronos also do another set which is as above but without the chuck and mounting plate and that is £236.80. I did ask Chronos if you can just buy the table without the extras but they said no its sold as sets. I did try finding the table only on line but couldnt find it so I assume Soba only supply it as a set.

I should say that I am not trying to promote or recommend this table to anyone it just suited my budget but what I have found so far is very good and seems good value for money.

Ron

Edited By Ron Laden on 22/03/2019 14:15:05

[Mick B1Participant @mickb1]

Posted by Ron Laden on 12/03/2019 20:00:25:

I have heard the term "rivet counters" is there such a thing as "micron chasers"..

I once went on a bodging course to make a Windsor chair on a pole lathe, from wood that started as a pile of fresh logs. We split, drawknifed and turned the legs, stretchers and sticks. We used spanners as the gauges for the location spigots on the turned parts.

One of the guys on the course had worked at a university lab, and he snorted at the crudeness of this: "Huh, I've worked to microns!"

Quick as a flash the instructor came back: "Yeah, and I've worked with morons!"

Bin lookin' fer a chance to use that …

[MeunierParticipant @meunier]

^^^ Thanks for that chuckle, MickB1

DaveD

[EmgeeParticipant @emgee]

Ron, if you ever need more height under the mill with the set-up shown you could mount the chuck direct to Tee nuts in the table slots, no need for the spacer plate with 4 front fixings through the chuck.

Emgee

[Ron LadenParticipant @ronladen17547]

Thanks thats a good point Emgee, I am not so bad off for height above the chuck providing the workpiece is not too tall and also with some tooling I could run out of space so losing the mounting plate would be a good idea.

Ron

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Emgee on 22/03/2019 21:14:44:

… with the set-up shown you could mount the chuck direct to Tee nuts in the table slots, no need for the spacer plate with 4 front fixings through the chuck.

.

That is a very good point

… I now wonder why they chose to supply that adapter plate in the 'package'

[Ron] … Does it have multiple fixing points for alternative chucks, or is it dedicated to that one ?

Just curious

MichaelG.

[Author]

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