rotary table problem

[larry PhelanParticipant @larryphelan54019]

Not sure if I,m doing this right,but here goes anyway.

Problem is this,I bought a new rotary table a few years ago but did not get to use it right away,due to a long term illness kicking in.

Later on when I got back to working and began to use the table,I found that it appears to be running off centre,hard to believe,I know. I could not machine even a simple hexagon ! I fitted a test bar in the centre hole and set up a dti and was surprised at the size of the run out. When I contacted the supplier I bought it from,the response was—Yep,you got it ! "Sorry,we no longer stock that product,and we cannot help you". Has anyone got any idea how to correct this? I find it difficult to understand how this could be drilled off centre to begin with. It is useless now except as a paper wt.

Needless to say,it would be totally useless for gear cutting,which is something I had in mind. Any ideas,you guys?

[larry PhelanParticipant @larryphelan54019]

[Nick HulmeParticipant @nickhulme30114]

Mill it in situ to accept a repair insert

[John HaineParticipant @johnhaine32865]

Do you mean that the hole is not concentric with the rotational axis? assuming you do, then your options are to avoid using the hole for centering, and/or correct it.

I would recommend anyway fitting a 4-jaw chuck to the table (if it has 4 tee slots) as this will allow you to accurately centre the blank before machining. If it doesn't have 4 tee slots you might consider drilling 4 bolt holes to suit the chuck – that's what I've done on mine even though it does have 4 slots. So, centre the work in the chuck just as if it was on the lathe, and away you go.

If you want to correct the run-out of the centre hole, if it isn't tapered you could do it on the mill, using an end mill or boring tool, rotating the table against the tool to slowly machine a new, larger true hole. If it is tapered it would probably need boring on the lathe, probably to the next size up.

Good luck!

[Michael GilliganParticipant @michaelgilligan61133]

Larry,

The responses so far seem very sensible … but a couple of questions, if I may:

1. What size & style is the table ?
2. … "Who sold you that then ?"

MichaelG.

[larry PhelanParticipant @larryphelan54019]

Thanks John,

I did try setting up a three jaw chuck,using the slots,with no better luck.Next time I will try the four jaw. I am just amazed that something like this could make it,s way through inspection [it came with it,s own cert,for what it,s worth ] Makes me wonder about the rest of the stuff out there !

I like your idea regarding the mill,that might be worth a try,since I really could make use of the table now,and at this stage,anything is worth a try.

Many thanks for taking the time to reply,

Larry Phelan.

[larry PhelanParticipant @larryphelan54019]

Hi Michael,

The table is a Homge 6 inch with three slots and mt centre hole..It was bought from Chester,like a lot more of my equipment. No problems with any of the other gear.They tell me they no longer sell this item and could offer no help with the problem,full stop ! Just shows that you need to check everything as soon as you get it home. Be warned !

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Larry

I don't know of Homge, but will certainly be wary of them; [not that I need another Rotary Table].

… as for the Certificate it's probably not worth the paper it's written on; but I would be interested to see a copy.

I would certainly try John's 4-jaw suggestion.

MichaelG.

.

Edit: It all looks very promising 

http://www.homge.com.tw/dividing.html

 

Edited By Michael Gilligan on 04/03/2017 13:31:50

[JourneymanParticipant @journeyman]

Homge is a Taiwanese company the have quite an extensive catalogue. It might be worth contacting them. Who knows they might send you a replacement or at least advise you of a UK or European stockist.

** Homge **

John

Edit: Michael got there before me with the link!

Edited By Journeyman on 04/03/2017 13:33:10

[John Stevenson 1Participant @johnstevenson1]

Homge is / was a well known brand, Myfords used to sell this version.

Not seen them for a while so don't know if they have ceased trading or been taken over by someone else.

In the early days , before cost cutting many makers used to use bearings on the worm shaft or if no room for bearing they would often use bearing thrusts.

Unfortunately as the bean counters and the punters who want more for less [ probably no difference between the two ] build quality was compromised.

I have converted literally 100's of rotary tables and diving heads over the years and Homge was one of the last ones to fit bearings. Even Vertex doesn't fit bearing any linger in fact they run a hardened steel worm direct into a steel eccentric housing, it used to be cast.

The only tabkes I know now that have bearings are the stepper driven CNC ones as sold by ARC but these have been retrofitted with needle roller bearing and needle thrusts by ARC.

Micheal, what good will seeing a certificate give you after you have already said it's not worth the paper it;s written on ?

Just pull the last two pages out of any Mills and Boone bodice ripper, it will contain the same fairy story.

[Neil WyattModerator @neilwyatt]

How big is the error?

Have you checked to see if the socket is bruised/burred inside?

Neil

[John Stevenson 1Participant @johnstevenson1]

Posted by Michael Gilligan on 04/03/2017 13:28:02:

.

Edit: It all looks very promising

**LINK**

Edited By Michael Gilligan on 04/03/2017 13:31:50

So they still do exist and I'll bet serious coin that Homge and the Vertex tables are one and the same seeing as they are both Taiwanese because Vertex is not a manufacturer but they rebadge other peoples products with their name.

A lot like Soba although Vertex use better donor material and have some form of quality control.

[John Stevenson 1Participant @johnstevenson1]

Posted by larry Phelan on 04/03/2017 13:04:55:

Thanks John,

I did try setting up a three jaw chuck,using the slots,with no better luck.Next time I will try the four jaw.

Larry Phelan.

.

A three or 4 jaw bolted to the table will be as accurate as the person setting it up, simple fact.

Ok the centre hole could be well off but as there is no register for the chucks they fit where you place them.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Stevenson on 04/03/2017 13:38:43:

Micheal, what good will seeing a certificate give you after you have already said it's not worth the paper it;s written on ?

.

John,

The certificate is evidence for, or against, my 'case' …

Larry mentioned a certificate, but did not tell us what it certified. … It is plausible ['though unlikely] that the certificate is so worded that Larry's table is within spec.

We all have our niche areas of interest; and one of mine is Probity.

MichaelG.

[EmgeeParticipant @emgee]

Larry

If the table base is fixed down does the outside diameter of the table run true when using the handle ? check with a dial indicator at the OD.

If it runs truly set it up and bore a new true plain hole at the table centre, if this hole is too big for your use make an insert to reduce the size.

Emgee

[Brian WoodParticipant @brianwood45127]

Larry,

​For what it is worth, I have a Myford 6 inch version which JS suggests was probably made by Homge.

​The Morse taper centre [2MT in my case] is a hardened bush and running badly eccentric from a poorly bored centre hole in the cast iron table. I corrected that by pushing out the bush and boring the centre hole true to the table rim, holding it in the lathe in a 4 jaw chuck, fitting a new bush in steel as a good fit in the newly bored hole and then machining a 2MT taper into that.

​The new bush is of course not hardened but it is true. Like others who have commented, fit a 4 jaw chuck and centre your work in that; as long as the table surface is flat and true that would be your best method of holding gear blanks for cutting teeth.
Regards
​Brian

[larry PhelanParticipant @larryphelan54019]

Hi Everyone,

Seems like I opened a right can of worms regarding my rotary table !

First off,my thanks to everyone who replied,at least I have hope now of correcting the problem. I took John,s advice and set up my 4 jaw chuck to do a test run [takes a while but was worth it ] The result was a perfect hex,so that would seem to indicate that the centre hole is off. [So much for spec ] M y 4 jaw is 8" dia with a threaded backplate which screws onto my lathe spindle.I used an adaptor which I had made long ago to use with a 5" chuck,in order to mount the 8" chuck.The adaptor is like a top hat,the flange being used to clamp it to the table using 3 clamps in the tee slots.I was of course locating from the centre hole,that,s when the penny dropped that all was not well.

I have three questions.

1 How do I go about bolting the chuck t directly to the table ?

2 How do I go about setting up the table to machine out the centre hole [which I would really like to do,would make things a lot easier later on ] How do I line it up with the spindle of the milling machine?

3 I suspect that the centre bush may be hardened,so may need to be pressed out. Any ideas how to do this without damaging anything else?

One extra question do I need to wind the table anti clockwise since the cutter will be going clockwise?

Sorry if these questions sound stupid,but I have learned over the years that it is much easier to deal with stupid questions than with stupid mistakes. [which we have all made,dont be shy! ]

Regarding the cert which came with my table a "precision" product,it was about as precise as a bicycle wheel with a hop in it.

Again,my thanks to all.I have come up with a few useful ideas over the years,which I would be happy to pass on if anyone is interested.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Neil Wyatt on 04/03/2017 13:43:16:

How big is the error?

…

Neil

Hi Iarry, before you jump in and cut metal, can you answer Neil's question? Just how bad is it (in mm or thou)? It could be relevant.

I ask because I had a similar run-out error on my rotary table / 3 jaw combination. I jumped to the conclusion that I had a problem with the centre hole; actually the chuck was slightly tilted. One of the chuck fixing bolts was slightly too long. That and trapped swarf was preventing the chuck from sitting flat on the table. It was not obvious at all.

A few minutes with a file and a good clean fixed it. Perhaps you might get lucky too.

Dave

[larry PhelanParticipant @larryphelan54019]

Hi Neil,

How big was the error? well,put it this way,there was no need to use a DTI !.A 6" rule would have been good enough,you could see it a mile away !.

The 5" chuck was screwed on to an adaptor and was sitting snug on the table.I have used the same chuck on my lathe,with no problem,no run out.. I might not have minded a slight run out,but this was ridiculous. The fact that the chuck and it,s mounting was located from the centre hole seems to point to the hole being off. I am not going to start cutting metal right away,before I check everything else. John,s idea did make a big difference,just takes a bit longer to set up each time,and the 8" chuck is huge!. Still,I am learning all the time and even at this stage, I can do a bit more with it now than I could before.I managed to machine a number of hex caps for a friend over the weekend. No idea what they are for,I just wanted to see if I could manage to machine them.

Seems such a pity to have a piece of gear like this and not to be able to make full use of it due to being badly made in the first place. I will continue to "Watch this space "

[SillyOldDufferModerator @sillyoldduffer]

Morning Iarry,

As they say, a picture is worth a thousand words. This is what was wrong with mine.

In the photo the adapter plate is fixed to the table and you can see the marks left by the overlong bolt through it's screw-hole. The effect of tightening the bolt was to lever the adaptor plate off the table and to tilt the chuck.

No names no pack drill, but I find I get better suggestions out of the forum by giving an accurate description of my problems. When I asked " Just how bad is it (in mm or thou)? It could be relevant.", I was hoping for something a tad more precise than 'A 6" rule would have been good enough,you could see it a mile away' !

That said, I sympathise. If it's half as bad as your description implies, you have a dud.

Good luck,

Dave

[larry PhelanParticipant @larryphelan54019]

Sorry if I seem to have have got off on the wrong foot,but when I said it was a mile off,I was not joking. I forget exactly how much it was off,but you could see clearly the difference on the sides of the hexagon,quite a lot of thous or mm. However,all might not be lost,following up on advice from Mike,I set up my 4 jaw chuck and had good results. This morning,I setup my 5" 3 jaw and set it to run true with the DTI. without ref to the centre hole. Again,the results were good,so it would seem that the centre hole is the culprit. Another man has explained how to set up to correct this error,which is something I will look at soon.

Again,my apologises ,God knows I can,t afford to annoy anyone,I know so little about the whole thing,but even I could see that I was not on a winner at that stage. How do these things ever get past "Inspection" ? is there any?

Larry.

[larry PhelanParticipant @larryphelan54019]

Hi Jim,

Thank you very much for your reply to my sad story table. The problem seems to be with the centre hole since I set up my 5" 3 jaw chuck this morning without ref to the centre hole and got good results. I..will now look at correcting this [why do we have to do such things with a new unit? ]

I would like to have the centre hole correct since it is useful for machining other work such as curved slots ect..Trying to do that as the table is,would result in some strange looking slots.

Many thanks to all you guys out there,you have given me much food for thought along with good advice. It,s nice to know that I am not alone in my efforts.

[Howard LewisParticipant @howardlewis46836]

Glad that you have overcome the immediate problem.

But, for the future, if you can, it would be ideal to find a means of resetting the 2MT bore on the centreline. Using the 2MT bore can be very useful for various tasks.

Judged by what you have said, so far, it seems unlikely that the Table is running eccentric in its bearings.

I would suggest clocking the 2 MT to find , and mark the sleeve and the table, WHERE it is eccentric, and noting by how much. Scribe the line hard, you may need it later.

It has been suggested to press out the 2MT sleeve fitting; then:

1) You can check if the locating OD and the 2MT bore are concentric. If they are, the problem lies with the bore in the table. (Vee Blocks and DTI or set the OD to concentric in a 4 jaw chuck before clocking the 2MT bore).

2) If the table bore is eccentric.

This can be fixed by boring the Table oversize, but off centre. (If there is sufficient metal around it) The depth of cut will vary until the eccentricity has been removed and the new bore cleans up all round. You then decide how much larger to make the bore for a sleeve to match the new bore to the OD of the 2MT sleeve. .

Set the bore to run true. Then move the bore off centre, in the opposite direction to the marked direction by half the measured eccentricity

You then bore a sleeve to be a tight fit on the 2 MT sleeve, and without changing anything (to keep the two machined surfaces concentric) turn the OD to be a tight fit in the enlarged bore in the Table.

Theoretically when you assemble everything the 2MT bore should now be concentric with the Table.

If you find that the 2MT bore is eccentric to its OD, you either need to turn, or more likely, grind the OD to make it concentric, before enlarging the bore in the table and turning up a sleeve to unite the reduced OD of the 2MT sleeve and the enlarged Table bore.

The real bodge would be to open up the bore in the Table, before turning a sleeve to be a tight fit, and then boring to be a tight fit on the 2 MT, BUT ECCENTRIC, so that when everything is reassembled IN THE CORRECT ORIENTATION, the 2MT bore then becomes concentric with the table.

However you fix the problem, it may useful to coat mating surfaces with Loctite or some other anaerobic locking fluid, to fill the tiny gaps in the machined surfaces, and to prevent any movement in future. If you choose the eccentric sleeve route; do get the orientation right. Once the anaerobic has cured, you will find it difficult, if not impossible, to press things apart, to reset the alignment.

Hope that this is some help.

Howard

[SillyOldDufferModerator @sillyoldduffer]

Posted by larry Phelan on 08/03/2017 14:28:02:

….

Again,my apologises ,God knows I can,t afford to annoy anyone

…

Larry.

Larry, my apologies too! I wasn't annoyed, you just bumped into my failure to make a point politely. Don't let me put you off asking questions.

Sorry again, I wasn't intending a poke in the eye.

Dave

[larry PhelanParticipant @larryphelan54019]

Hi everyone,

Back to the old rotary table [OK,I can hear you all saying "not that again" ] The good news is that when I had finished a job with it last weekend [using the 4 jaw chuck setup ],I set it up with a best bar in the centre hole and clocked it. The hand got dizzy going around the dial ! The truth is that it was/is out by 25 divs,each one 0.01mm,a total of 0.25 mm. A bit much,you might say. This is much as I seem to remember it was the first time I checked it;

Hence my referring to the 6" rule ! A micrometer would have been an overkill,perhaps a 4"g clamp might have more suitable. Anyway,I now have a good idea of how to correct the problem,so all may not be lost.My thanks to everyone who gave a hand. Someone asked about the cert which came with it,so I will try and enclose a picture of it.While all the tests are marked off as OK, you will note that no one signed it ! I wonder why?

Sorry,was unable to get the picture out from my picture files. [I can hear you guys saying "can this guy do anything? ].

[Author]

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