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Soba rotary table

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JasonB13/03/2019 10:11:41
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Posted by Andrew Evans on 13/03/2019 09:05:18:

If one wanted to purchase a new, high quality, small rotary table what are the options?

Think you may just get a bit of change out of £3k for a 6" Bison one but have not looked up the spec or where they are actually made.

Edited By JasonB on 13/03/2019 10:27:02

JasonB13/03/2019 10:14:35
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Ketan gets his from factory S who may well get from factory D and his do cost more than a similar size Vertex which does put people off buying them as comments on here have shown and is probably whey he is looking to add a lower budget one to his wares.

The problem is if he buys from Factory A to get the best quality people will just look at it and think it is the same as all the others and a lot will just base their purchase on price. His factory A will cost more than factory C and be better but may not compete with BG etc.

Edited By JasonB on 13/03/2019 10:25:04

Mike Poole13/03/2019 10:17:29
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It always makes me smile when a guitarist finishes tuning his guitar and says “it’s close enough for jazz” I think I must be a jazz player.

Mike

Andrew Evans13/03/2019 10:24:38
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6 inch Bison rotary tables are £2700! I guess that shows what you pay for quality.

JasonB13/03/2019 10:26:53
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That's what you get for looking at costs 2 days ago, you forget the odd £1000blush

And from the specs on Rotagrips site not upto Stephan's level of accuracy

Edited By JasonB on 13/03/2019 10:29:12

Hopper13/03/2019 11:18:32
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Posted by geoff walker 1 on 13/03/2019 09:23:31:

On accuracy this table is 7.5 degrees out over a full 360 degree rotation of the table. The hand wheel dial is indexed with 7.5 degrees and the hand wheel rotates exactly 47 times for one rotation of the table, should of course be 48.

LOL. Cost saving measure. One tooth saved on each worm gear means that every 47th gear they get one for free. cheeky

I bet you had some headaches until you worked that one out though. Who would think to check that?

not done it yet13/03/2019 11:22:29
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I bought my 150mm vertex rotary table probably more than ten years ago. It laid unused in the airing cupboard for several years but now gets used quite often.

Nice to know that it may well be a better example, but I still treat it with care when in use. It is not a cheap item to replace, if abused and broken!

With regard to quality,I relate to Ketan's posting in that wherever there are multiple stages between casting and retailing, there will always be some rejects at each quality assurance stage. It is really sad that the rejects are simply directed down another production path and many still find their way to unsuspecting purchases, from those that buy the cheapest and sell similar "looking" items (to the rel McCoy) at rock bottom prices.

These days one can likely be assured that, if cheap and cheerful, your product was rejected (by a more discerning manufacturer) for some reason, at some stage of its production. Either that or the item has been constructed with cheaper parts.

From this thread it appears that the OP's item may have been rejected more than once! Buying from the likes of bang good likely guarantees that, although there are obviously plenty more opportunities to get caught out. that said, some of the rejects may be suitable for the job they were bought for.

Oxymoron13/03/2019 14:23:26
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I have recently been looking at rotary tables for use on my mill (SX2.7). This discussion has been very useful to me.

However a question: Some tables seem to be sold with dividing plates and I am wondering if these are actually needed. In my imagination rotary tables can be positioned to within a few seconds of angle. So why are dividing plates needed as surely a spreadsheet could quickly give the number of degrees, minutes etc for any number of divisions.

What have I missed please, are dividing plates worth having with a Rotary table?

Regards

Dave

JasonB13/03/2019 14:49:30
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Again it depends on what you are doing with the table, machining curves and doing simple things like PCD spacing does not need them but when it comes to say gear cutting it is a bit easier and less error prone to use the plates. If I remember rightly I bought my table and used it for a while as just that then when I had some gears to cut added the plates and tailstock.

thaiguzzi13/03/2019 15:03:26
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I bought my HV6 Vertex new in the early 90's. It was worked hard in a professional shop until 2003 when i retired it to hobby use along with myself.

So that's well over 25 y/o.

I still have all the paperwork, instruction manual, and factory inspection data.

I also have period early 90's Vertex product brochures.

It was most definetely made in Taiwan.

Neil Wyatt13/03/2019 15:04:22
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Posted by Oxymoron on 13/03/2019 14:23:26:

I have recently been looking at rotary tables for use on my mill (SX2.7). This discussion has been very useful to me.

However a question: Some tables seem to be sold with dividing plates and I am wondering if these are actually needed. In my imagination rotary tables can be positioned to within a few seconds of angle. So why are dividing plates needed as surely a spreadsheet could quickly give the number of degrees, minutes etc for any number of divisions.

What have I missed please, are dividing plates worth having with a Rotary table?

Regards

Dave

Shh... it gives people a great deal of comfort to know they can work to a level of precision far higher than the accuracy of their equipment

Seriously though, they can make dividing quicker or less error prone, but things like vernier adjustments and worrying about rounding errors is pointless for 99.9% of work. I've only ever made gears working to the nearest 0.1 of a degree (ten seconds) which is within a thou at the edge of a 2" diameter gear.

Neil

Edit: Looking at the comments above, it really does matter to match the precision you work to to the job in hand. Working to a precision significantly greater than the process you are using or the capability of the tooling might give you a warm glow, but in reality it's just a waste of effort better put into some other aspect of the work.

My astronomy hobby has taught me an awful lot about working with different levels of angular accuracy. You need to be within about a degree to find objects. You might work to a few arc-seconds to accurately align them in a camera frame. You work to seconds of a degree when tracking, which needs constant error correction. With the clock ticking it's pointless to work to more accuracy than you need.

Edited By Neil Wyatt on 13/03/2019 15:19:29

Michael Gilligan13/03/2019 15:13:04
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Posted by Neil Wyatt on 13/03/2019 15:04:22:
... to the nearest 0.1 of a degree (ten seconds)

.

dont know

Oxymoron13/03/2019 15:13:16
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Thanks Guys. Pretty much as I assumed, you can manage without the plates but they make it easier. And less error prone. I need all the help I can get!

geoff walker 113/03/2019 15:14:43
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Posted by geoff walker 1 on 13/03/2019 09:23:31:

On accuracy this table is 7.5 degrees out over a full 360 degree rotation of the table. The hand wheel dial is indexed with 7.5 degrees and the hand wheel rotates exactly 47 times for one rotation of the table, should of course be 48.

LOL. Cost saving measure. One tooth saved on each worm gear means that every 47th gear they get one for free. cheeky

I bet you had some headaches until you worked that one out though. Who would think to check that?

Hi Pete,

Yes I did have some headaches!!!

When I first got this table I set the 0 on the circumference dial to the cursor and 0 on the hand wheel dial to the cursor, then turned the table through 360 degrees and much to my astonishment the dials lined up again. I thought WOW!!! that's accurate. Of course at the time I didn't realise that I was one turn short, 47 x 7.5 degrees and not 48.

The table has a cumulative error of 1.25 minutes per degree of revolution.

As I said in the original post I can still use table by making a coarse setting with the circum dial, which is accurately engraved and a fine setting with hand wheel dial. So for say 132 degrees turn 130 on the circum dial and 2 on the hand wheel dial. This gives me "theoretically" 132 degrees with an error of 2.5 minutes which is fine for what I do

Geoff

Andrew Johnston13/03/2019 15:43:47
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Posted by Michael Gilligan on 13/03/2019 15:13:04:
Posted by Neil Wyatt on 13/03/2019 15:04:22:
... to the nearest 0.1 of a degree (ten seconds)

dont know

I think we should minute that for future reference. smile

Andrew

JasonB13/03/2019 15:54:21
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Posted by Michael Gilligan on 13/03/2019 15:13:04:
Posted by Neil Wyatt on 13/03/2019 15:04:22:
... to the nearest 0.1 of a degree (ten seconds)

.

Don't point that out to him Michael, he is now going to realise that he has set his telescope wrongly too and been looking at the wrong planets for the last couple of years and what he thought was Uranus was something completely different

Michael Gilligan13/03/2019 16:07:17
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Posted by JasonB on 13/03/2019 15:54:21:
... was something completely different

.

in the elbow constellation ?

not done it yet13/03/2019 16:11:38
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Posted by Michael Gilligan on 13/03/2019 15:13:04:
Posted by Neil Wyatt on 13/03/2019 15:04:22:
... to the nearest 0.1 of a degree (ten seconds)

.

dont know

Nearer 2 thous if 1/10 th, and almost 3 thous if 10 seconds - to the outer edge of a 2" circle?

One might only need a mirror, JB?smiley

Chris Trice13/03/2019 16:20:29
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Posted by geoff walker 1 on 13/03/2019 09:23:31:

On accuracy this table is 7.5 degrees out over a full 360 degree rotation of the table. The hand wheel dial is indexed with 7.5 degrees and the hand wheel rotates exactly 47 times for one rotation of the table, should of course be 48.

I'd argue this qualifies it as worthless junk since it renders many of the tasks a rotary table is reasonably expected to do as unreasonably difficult and therefore not fit for purpose. I'm sure if your life depended on it, you could achieve all sorts of miracles using it if you had to but you shouldn't have to, regardless of how cheap it was.

JasonB13/03/2019 16:25:24
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Posted by not done it yet on 13/03/2019 16:11:38:
Posted by Michael Gilligan on 13/03/2019 15:13:04:
Posted by Neil Wyatt on 13/03/2019 15:04:22:
... to the nearest 0.1 of a degree (ten seconds)

.

dont know

Nearer 2 thous if 1/10 th, and almost 3 thous if 10 seconds - to the outer edge of a 2" circle?

One might only need a mirror, JB?smiley

10 seconds would be quite a bit less, 10 mins would be about 3 thou.smile p

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