Run out on a rotary table

[JourneymanParticipant @journeyman]

Dave, given that my website gets relatively few hits, I think your viewing probably puts readers of that article up to about ten, statistically very unlikely. Then again you know what they say about statistics!

John

[SillyOldDufferModerator @sillyoldduffer]

Posted by Journeyman on 30/03/2017 13:09:10:

Dave, given that my website gets relatively few hits, I think your viewing probably puts readers of that article up to about ten, statistically very unlikely. Then again you know what they say about statistics!

John

Oh dear! I've read the article twice which completely wrecks the sample population. Shame no-one else has noticed your website, it's a good 'un.

I first got to the website a few days ago via another thread discussing reducing backlash in rotary tables. I've not thought it through, but I think with an Arduino/Stepper motor it should be dead easy to compensate for any backlash in software. For example, my table has 12 minutes of backlash. All that's needed is to change the sketch to emit the corresponding number of extra steps whenever the motor changes direction.

Armchair theory so far. I've not managed to connect motor and table together yet. I've loads of good excuses for not getting on with it but the real reason is that I'm easily distracted!

Dave

[SillyOldDufferModerator @sillyoldduffer]

Final Report on Rotary Table run-out and cutting a pentagon.

This time I set the table up with no tailstock and with a length of old hacksaw blade stuck between the rod and one jaw in the chuck. This caused a whopping 1mm run-out where I cut the hexagon. On a 10mm diameter rod, this is a 10% error. On a 50mm gear wheel, it would be a 2% error. I used the upper flutes of a 12mm carbide cutter and took a 0.9mm cut at 2000 rpm.

Results were fairly good.

The flaws are much easier to see in real-life than in the photo. However:

• Leftmost was made with the most rigid setup. Finish, centricity and dimensional stability are all good.
• Middle example was cut unsupported. Centricity is acceptable, finish and dimension stability are both somewhat compromised. It looks rough and is!
• Rightmost example was cut unsupported and with 1mm runout. The finish is good, demonstrating perhaps an advantage of carbide cutting at speed. However although the pentagon has good shape, it's eccentric, surprise, surprise! This pentagon is also undersized at 8.7mm vs 9.2mm (target 9.1mm) I'm not sure why carbide should cut deeper than HSS at the same setting, unless it's operator error.

For use as a security key I would say the pentagons are all acceptable. Where it matters only the fully supported example has any claim to precision.

Dave

[Iain DownsParticipant @iaindowns78295]

After a little while I've got a response from WARCO. It seems the delay was caused by them trying to get information from the manufacturer on my question. Not with much success, though they did identify that the bolts on the back weren't for adjustment.

They have offered a refund as they don't have any stock for replacement. Good news and excellent service.

However, before I send this table back I wanted to ask the forum if I am likely to get any improvement by using my refund (about £120) to contribute to another table.

Is it a friday afternoon HV4? Or all all days in China Friday Afternoon. I don't much mind putting a bit more in, but I'm not up for Mr Stevenson's 3 grand quality rotary table – that's several years' budget!

Arguably, I could buy a tailstock and use a collet to get accurate results, but that's a bit of a faff.

I liked this one because it came with dividing plates and a 90:1 worm (and was a now understandably good price).

ARC's equivalent (which is most likely quite good) is over 300 quid.

Any good / bad experiences out there?

Many thanks

Iain

[Tim StevensParticipant @timstevens64731]

Next question – has anyone a use for several lengths of BMS with polygons of somewhat variable quality towards one end?

A very interesting discussion. I will look more closely at my rotary table tomorrow,

Cheers, Tim

[JonParticipant @jon]

For reference my old 1998 Vertex HV8 is on bearings and adjustable.

No RT will suffice unless rigidly clamping the job true.
Means have to be able to move any chucks to centre up off the job and bolt down. Mine is also one of the 4 slot types, since its for a specific purpose the 3 jaw chucks bolted through and tapped direct into the table only removed once in 18 years.

Mounting mine horizontally is a pain with two elongated side slots, have to use shallow studs in to T nuts and nut other end as cant get a bolt through in to a T nut.

[Iain DownsParticipant @iaindowns78295]

As a constraint, I should note that my mill is a CMD10 with a 240x150mm table (and a little less travel).

An 8 inch vertex would leave not space to work!

Even the 4 inch vertex is nearly too big for the machine.

Iain

[larry PhelanParticipant @larryphelan54019]

Hi Ian,

Glad to see that you got some response from Warco,that,s a bit better than I got from Chester. Regarding the cost,if these things dont work,what the hell use are they ?. At least you were offered your money back,but dont expect to get anything better for that price. It seems to me that these items are just being flogged off to make us feel good,never mind the quality. Monday morning/Friday afternoon what,s the difference? These days if I get something which works,I tend to look at it twice [surprise surprise ]. To get a table which would really work right,it seems you need to pay big bucks,and unless you have the work for it,you can,t afford it,few of us can,but we should still be offered something better than the junk on sale.

I shall continue to watch Warco.

Edited By Neil Wyatt on 09/04/2017 19:26:13

[Howard LewisParticipant @howardlewis46836]

As a bit of an aside to this thread, the mounting slots of my HV6 were lengthened, to allow more movement across the Mill table.

I don't use keys to locate the HV6, (Can sometimes be restrictive of positioning; preferring to set the Table on the Mill table with a square. See Photo 1 on p age 40 of M E W Issue 252 (The one printed as 251 for the second time)

If you want a consistent positive location, instead of a key, two dowels can be used, The dowels will probably need to be stepped to match the slots in the Rotary table, and the T slots in the Mill table.

To locate the Tailstock consistently, I did not use keys, but made up stepped dowels, retained by hex head bolts in the tapped holes visible in the upper illustration on the 30-3-2017 11:52 03 posting.

For a picture of the set up, see Photo 3 on page 40 of M E W Issue 252.

Have to admit that have never been aware of any run out , (never looked for any), and the end results seem to satisfactory. So seem to have been luckier than the O P, but have experienced some absolutely appalling run outs on other simple parts, am aware that oriental quality can be variable.

Howard

[Neil WyattModerator @neilwyatt]

Oh well, I accept they are for keys

Not that i can see how you fit a key to the top of the T?

I note there is a camping slot on the other face in the drawing!

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Much too big for most of us

But, as a point of reference …

This is a seriously good Rotary Table

http://www.ebay.co.uk/itm/172569854011

MichaelG.

Edited By Neil Wyatt on 09/04/2017 19:26:39

[Iain DownsParticipant @iaindowns78295]

It's been a while since I started this thread and I wanted to report that I've had a replacement table from WARCO.

The delay was waiting for the tables to come into stock. Apart from anything else the new tables have a half reasonable manual and if the schematic is to be believed bearings!

This table is MUCH better. I measured the run out at 50mm on a piece of 6mm test bar (from a scanner) in an MT2 collet. I did two sets of measurements – the second after carefully turning the bar by 90 degrees (to make sure the bar wasn't bent).

The first test I saw an error of less than 2 thou (about 0.045mm) and the second test was better with no more than 1 though run out.!

This contrasts to a considerably larger error with the previous table so i'm delighted. Of course the other comments (use of tailstocks etc) still apply if I do something delicate with it.

My thanks to WARCO who have been very helpful and professional.

Iain

[Michael GilliganParticipant @michaelgilligan61133]

Good result, Iain

MichaelG.

[larry PhelanParticipant @larryphelan54019]

Just reading the post from the guy who received his replacement rotary table from Warco.

Good for you ! just as well you were not dealing with Chester !

I was able to measure the run out on my table with a 6" rule,no kidding!

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