Soba rotary table

[Ron LadenParticipant @ronladen17547]

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

[Ian Skeldon 2Participant @ianskeldon2]

I don't think I will ever have to worry that a shaft or bearing face is one hundredth of a millimeter out, and if I did I am really sure I don't have the time, equipment or skill to improve it, so maybe that vertex would be a good item for me to buy.

Ketan, do you sell Vertex?

Ian

[Howard LewisParticipant @howardlewis46836]

Ketan,

You have cheered me up, a lot. I was beginning to worry about my elderly Vertex HV6. Having always used mine in "Plug and play" mode, (Ignorance is bliss); began thinking "Should I have checked for, or noticed, any of these problems"? And then you came along and said that the old ones were probably made in a better factory than the more recent ones.

As in so many things, we tend to get what we pay for, you don't get a Rolls Royce for a Reliant price!

Really, the question becomes "Is it fit for purpose?, and "Is it value for money?" If the answer to both is "Yes" then end of discussion. Use it, subject to its known limitations. If the answer is "No" then action of some sort needs to be taken; either to modify / improve the object until the answer becomes "Yes" or to dispose of the thing, in a way which is controlled by your ethics and your budget. (Sell, "as seen", "faults declared", or in silence, or scrap. )

I use an elderly (from new ) RF25 Mill/Drill. It weighs about 150 Kg and does not have the features or rigidity of a 2 ton Cinncinatti vertical mill. I could not afford such a machine, or have the space for it, and would not use all its capabilities.

So, I make the best of what I can afford and can accomodate, recognising the limitations that are self imposed

Howard.

Edited By Howard Lewis on 12/03/2019 20:24:26

[Michael GilliganParticipant @michaelgilligan61133]

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"..

.

Well … Roderick Jenkins used it in a post here in 2016, so I suppose there must be.

https://www.model-engineer.co.uk/forums/postings.asp?th=120217

But the real question is:

Is it intended as a term of abuse? … and if so: Why?

MichaelG.

 

Edited By Michael Gilligan on 12/03/2019 21:59:40

[Bill PhinnParticipant @billphinn90025]

Posted by Michael Gilligan on 12/03/2019 21:59:11:

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"..

.

But the real question is:

Is it intended as a term of abuse? … and if so: Why?

MichaelG.

I'd say it's legitimately pejorative when chasing microns means aiming for a level of precision that is considerably in excess of what is required for the satisfactory functioning, or satisfactory appearance, of the item being made.

On the other hand, though speaking pejoratively in these circumstances has reason on its side, it fails to take account of the potentially high levels of satisfaction experienced by some people when they aim for and achieve a higher level of precision than is strictly necessary for reasons of form or function; achieving such satisfaction might be rightly considered an end in itself.

And then there are circumstances, which perhaps few home machinists meet with in real life, in which very high levels of precision definitely are called for and to achieve which you may well have no alternative but to chase microns.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the intelligent reply, Bill

To elaborate a little: The difficulty I have is that people seem to be biased towards their own 'scale' of working, and are blind to the interests of others.

If you are cutting a 1 metre length of Steel bar, I doubt if many here would consider +/- 1mm an unrealistically tight tolerance; likewise a 100mm rod dimensioned to +/- 0.1mm is unlikely to raise eyebrows.

As it happens, I am interested in smaller things … so I need to work to similar proportions: If the item is only 1mm long, why should I not expect to need to work to +/- 1 micron ? < et seq. >

Tonight I was examining some red Blood Cells … typically about 7.2 micron diameter and a couple of microns thick.

The focus mechanisms on several of my microscopes have scale divisions of 1micron [and some of these are older than me] … This is not some impossible flight of fancy, it is a basic mechanical device, doing its necessary job.

To do useful image stacking on those cells, I expect to shift the focus in steps of half a micron or less.

Yes 'chasing microns' when working at the metre scale, or the 100mm scale might be considered unrealistic; but it is not, of itself, something to be ridiculed or disbelieved.

MichaelG.

[Paul KempParticipant @paulkemp46892]

Michael,

I have absolutely no problem striving for accuracy and precision where it is necessary for the function of the output of the job. Certainly accuracy and precision in carrying out work is a mark of professionalism and craftsmanship and something I was taught in my apprenticeship. However I was also taught in subsequent years that tight tolerances cost money in the real world, may require a completely different machining process to achieve such as final precision grinding to gaurantee size and finish. It is also true as stated that some people derive satisfaction and pleasure purely by making something to the nearest 10th of a thou.

What often galls me though is the opposite attitude to the one you present where you suggest people are unable to appreciate scale of activities and the need for tight tolerances, that opposite being the people who indulge this activity commenting on the value, suitability, fitness for purpose of various machines and tooling from that perspective. The plain fact is outside micro biology and other fine engineering tasks like watchmaking is the steam engine fraternity, IC engine fraternity, motorcycle restorers and repairers and general back yard shed tinkerers who can turn out perfectly adequate jobs working to the nearest thou and be equally proud of them too.

It seems to me sometimes on this forum especially where outrage or surprise is expressed because there is half a thou play in say a rotary table that to an extent that attitude is encouraged and bred by the micro brigade sowing the seeds. A fair proportion of people and probably an increasing proportion in the future do not come from a background where they can recognise what is an appropriate tolerance to apply to a task and often the advice given on here errs on the finer side of the fine line!

We all have our own interests and reasons for doing what we do and come from different backgrounds with different levels of experience. It strikes me from several recent posts that perhaps all sides need to be a little more tolerant and have a slightly wider perspective.

Paul.

[HopperParticipant @hopper]

Posted by Michael Gilligan on 13/03/2019 00:23:57:

Thanks for the intelligent reply, Bill

…

Tonight I was examining some red Blood Cells … typically about 7.2 micron diameter…

So we're counting tenths of a micron now.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 13/03/2019 02:55:54:

Posted by Michael Gilligan on 13/03/2019 00:23:57:

Thanks for the intelligent reply, Bill

…

Tonight I was examining some red Blood Cells … typically about 7.2 micron diameter…

So we're counting tenths of a micron now.

.

Yes, Hopper … and also [if appropriate] 'what follows'

That's why I wrote:

As it happens, I am interested in smaller things … so I need to work to similar proportions: If the item is only 1mm long, why should I not expect to need to work to +/- 1 micron ? < et seq. >

MichaelG.

.

P.S. You may be amused to know that the mean volume of a red Blood Cell is commonly expressed in femto litres, and that the typical healthy cell is then in the range 80-100 [so yes, it's often 'manageable proportions' that guide our choice of 'units of measurement']

https://en.m.wikipedia.org/wiki/Mean_corpuscular_volume

https://en.m.wikipedia.org/wiki/Femtolitre

Edited By Michael Gilligan on 13/03/2019 07:40:30

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Paul Kemp on 13/03/2019 01:17:23:

We all have our own interests and reasons for doing what we do and come from different backgrounds with different levels of experience. It strikes me from several recent posts that perhaps all sides need to be a little more tolerant and have a slightly wider perspective.

.

Amen to that, Paul

A forum like this should be a good place to share knowledge and experience, for the common good.

MichaelG.

[JasonBModerator @jasonb]

I think Bill and certainly Paul have summed things up very well, there is a place for very fine work but if you don't know what the person asking needs giving an abrupt answer can be confusing.

To say "I would not want it" or "It's C**p" without qualifying that you work to the nth degree will make that person think their tool is no good and should go back. Conversly to say what can be done on a similar or the same tool particularly with first hand experience of using one will give them the option to decide if it will be OK for their particular use or if it needs to go back as they think they need something more accurate.

J

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 13/03/2019 07:31:09:

I think Bill and certainly Paul have summed things up very well, there is a place for very fine work but if you don't know what the person asking needs giving an abrupt answer can be confusing.

To say "I would not want it" or "It's C**p" without qualifying that you work to the nth degree will make that person think their tool is no good and should go back.

.

In my defence, Jason …

My statement was [or so I thought] clearly qualified by the words following "But:"

and I never suggested that it should go back … Quite the opposite: I even quoted John Stevenson's mantra !!

If that was not sufficient clarity for Neil Lawton: I apologise unreservedly.

The fact remains that I wouldn't want the table in question, but that's not to say it would not suit his purpose.

MichaelG.

[Ron LadenParticipant @ronladen17547]

Posted by Michael Gilligan on 12/03/2019 21:59:11:

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"..

.

Well … Roderick Jenkins used it in a post here in 2016, so I suppose there must be.

**LINK**

But the real question is:

Is it intended as a term of abuse? … and if so: Why?

MichaelG.

Edited By Michael Gilligan on 12/03/2019 21:59:40

Michael,

Not intended as a term of abuse at all I was just been a bit naughty and I understand any person wanting the very best tooling even when they probably never work to the tolerances the tooling is capable of. Knowing that they have tooling cable of that level of accuracy is what interests them and gives them pleasure, thats fine with me.

I dont know what level Neil is looking for but I suspect he was surprised to find the error he did, his table may be absolutely fine for his type of work, maybe not, he doesnt say.

Ron

[Andrew EvansParticipant @andrewevans67134]

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

[geoff walker 1Participant @geoffwalker1]

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.

I have read all of this thread with interest but particularly liked this post from Paul. Sums up My attitude!!

I bought this small rotary table from GDR some months ago and despite it having numerous faults it's ok for me and the standards I need to set when making my models. I've had to modify and improvise to make it usable but as I have said before it was "cheap as chips".

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 get round this by using the scale on the circumference of the table. For say 92 degrees I advance 90 degrees and then add 2 degrees from the hand wheel dial. that's accurate enough for me and the work I do

Cheers Geoff

[Douglas JohnstonParticipant @douglasjohnston98463]

It is always very interesting to read Ketan's comments about various manufacturers/sellers as he has first hand knowledge about the subject. So much has been said about poor Chinese quality, much of it probably unjustified, so it is good to know some of the background to the price/quality issue. A brand name like Vertex can give the average person the idea that they are the manufacturer, whereas they are simply a buyer from some factory, and as the price goes up they can simply switch to a cheaper source.

I bought my Vertex rotary table about twenty years ago and it appears very well made. It may well have come out of factory A, but I have no way of knowing and it makes the whole buying game a bit of a lottery. If ARC were to buy from factory A, as we would all like, how many people would pay the higher price? I can well understand why Ketan has been thinking about this for so long. Perhaps the only answer is for companies like ARC to supply a cheap model and a more expensive one with a clear description about the quality of each, but then again this might not make commercial sense.

Doug

[JasonBModerator @jasonb]

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

[JasonBModerator @jasonb]

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 PooleParticipant @mikepoole82104]

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 EvansParticipant @andrewevans67134]

6 inch Bison rotary tables are £2700! I guess that shows what you pay for quality.

[JasonBModerator @jasonb]

That's what you get for looking at costs 2 days ago, you forget the odd £1000

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

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

[HopperParticipant @hopper]

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.

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

[not done it yetParticipant @notdoneityet]

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.

[OxymoronParticipant @oxymoron]

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

[JasonBModerator @jasonb]

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.

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