Thread: AL-320G Tailstock high

I remember buying a Vertex rotary table...

Looking at the inspection chart.... Someone somewhere posted a copy of their inspection chart for an identical vertex rotary table except it was something like fifteen years older.... Totally identical..

Thanks everyone for the replies. I took the tailstock apart and found a slight burr on the bolt hole which I carefully filed down and tested again. This time the tailstock was .04mm high so, acting on the advice given here, I have decided to leave it alone.

The setup I used to test is shown in the photo. I mounted an ER collet in the headstock with a short test rod inserted. I screwed a piece of alum angle to this and then bolted a short alum bar to that. In the tailstock I mounted a drill chuck arbor. I indicated on the flat section of the JT2 arbor.



P1060983.JPG

BTW I didn't receive a "Test Certificate" with my machine.

Thanks,

Kevin

Originally Posted by newmanwoodlands

The setup I used to test is shown in the photo. I mounted an ER collet in the headstock with a short test rod inserted. I screwed a piece of alum angle to this and then bolted a short alum bar to that. In the tailstock I mounted a drill chuck arbor. I indicated on the flat section of the JT2 arbor.

I'm trying to work out how you determined the tailstock was 0.04 mm higher than the headstock based on that setup?

Looking back not even worth the effort to set up an indicator to start with,how well does the collet chuck run,then the collet then the rod attached to the collet and then the drill arbor in the tailstock and finally the indicator.

Originally Posted by pipeclay

Looking back not even worth the effort to set up an indicator to start with,how well does the collet chuck run,then the collet then the rod attached to the collet and then the drill arbor in the tailstock and finally the indicator.

Pipeclay, it does indeed NOT matter how round the collet or its chuck or the rod or the indicator runs. Because these parts all rotate around the spindle axis!

Yes the arbor in the tailstock matters. But assuming the mating surfaces of the taper were clean and free of dents, such drill chuck arbors are usually ground to better than 0.01 hundreds of a millimeter. In doubt it is easy to rotate that arbor and repeat the measurement, that will instantly reveal any error. If the OP only has a dial indicator at hand, he has to use an arbor to make a measurement.

Originally Posted by .RC.

I remember buying a Vertex rotary table...

Looking at the inspection chart.... Someone somewhere posted a copy of their inspection chart for an identical vertex rotary table except it was something like fifteen years older.... Totally identical..

Here the test report for my Vertex 6" RT, bought from Machineryhouse in 2011. It will be interesting to see what the reports from other members look like.

Vertex.jpg

There are indeed a few items that look somewhat fishy:
- no date (EDIT there is a date inside each of the stamps at the bottom)
- no serial number (Vertex rotary tables have no serial number though...)
- no human signature, just a rubber stamp
- the measurements are entered with a rubber stamp. They are normally either entered in handwriting, or come as a printout strip from an automated tester in the case of mass produced items.

EDIT: on the upside, the blue rubberstamps are water soluble, unlike the rest of the form. This means they were individually stamped by hand, not printed as a whole with the form. And this would mean that there should not be a second test report looking exactly the same.

Originally Posted by .RC.

I remember buying a Vertex rotary table...

Looking at the inspection chart.... Someone somewhere posted a copy of their inspection chart for an identical vertex rotary table except it was something like fifteen years older.... Totally identical..

This thread?

Which 6" import rotary table?

All the test figures for the 22/11/1994 dated test certificate for my 6" Vertex table and the inspectors' signatures are identical to the ones in the 2005 test certificate shown in post 5 in the linked thread. The photo has gone from R C's post in that thread, but, if I remember correctly, he mentioned that his certificate for an 8" table also showed identical figures.

Anyone else still have the test certificates for their Vertex 6"/8" tables? It would be interesting to know if there was ever any variation from any of the figures in the posted test certificate, or inspectors' names.

Looking at CBA's 2011 test report in post 22 (which appeared while I was originally typing this), it seems that they have been remarkably consistent in their figures over 17 years - only the inspectors have changed!

Frank.

How do I delete the unwanted image?

F S

Originally Posted by cba_melbourne

Pipeclay, it does indeed NOT matter how round the collet or its chuck or the rod or the indicator runs. Because these parts all rotate around the spindle axis!

Yes the arbor in the tailstock matters. But assuming the mating surfaces of the taper were clean and free of dents, such drill chuck arbors are usually ground to better than 0.01 hundreds of a millimeter. In doubt it is easy to rotate that arbor and repeat the measurement, that will instantly reveal any error. If the OP only has a dial indicator at hand, he has to use an arbor to make a measurement.

Okay then my bad again sore hands and more hanging time.

Unless this bloke is working for some type of space agency or similar on a sh-ty chinese lathe as most here have does a bit of run out really matter,I think not.

And if it was high precsision it would be on a decent machine.

Originally Posted by franco

This thread?

Which 6" import rotary table?

All the test figures for the 22/11/1994 dated test certificate for my 6" Vertex table and the inspectors' signatures are identical to the ones in the 2005 test certificate shown in post 5 in the linked thread. The photo has gone from R C's post in that thread, but, if I remember correctly, he mentioned that his certificate for an 8" table also showed identical figures.

That is impressive you found that..

Here is the missing photo from mine..

rotary tables001.jpg

here is the report that came with one of mine only last year .

johnoScan.jpg

Originally Posted by cba_melbourne

Pipeclay, it does indeed NOT matter how round the collet or its chuck or the rod or the indicator runs. Because these parts all rotate around the spindle axis!

Yes the arbor in the tailstock matters. But assuming the mating surfaces of the taper were clean and free of dents, such drill chuck arbors are usually ground to better than 0.01 hundreds of a millimeter. In doubt it is easy to rotate that arbor and repeat the measurement, that will instantly reveal any error. If the OP only has a dial indicator at hand, he has to use an arbor to make a measurement.

You cannot rotate a dial indicator around any type of centre or arbour in the TS and determine a height difference from that. The droop of the indicator and fixture will make the height appear off (indeed appear, surprise surprise, TS high). Side to side, yes no problem (albeit with care), but not top bottom.

The appropriate way is to use a precision test bar between centres and indicate the top of the bar at the headstock and tailstock ends. As most won't have a test bar, never mind a truly accurate one, a "cheat" is to turn your own "test bar" with accurate centres and indicate off a specific point at the top of the bar, say at the TS end. Remove the bar and turn it end for end, replace the bar and indicate off the same point. Normally with a test bar you can traverse up and down a little to make sure there's no crud anywhere and this won't be applicable in this instance, but it will be a lot more accurate than swinging a noodle around the TS and wondering why it's high!

Hopefully that helps reduce the possibility of an angle grinder being taken to another lathe. I've just been called in to work, so am frantically rushing about getting ready, so sorry if there's typos etc. I'll try not to edit later lest it upsets those who waste their life hovering over their keyboard alternatively hitting the refresh and Google buttons

So far, looks like all inspection reports are subtly different. On some the names of the testers are the same, but each signature is slightly different and individual. It the reports were fakes, they would have to be identical prints. It just does not make sense to go to all the trouble making individually different fakes. I would call them genuine.

Also, Vertex has earned a reputation among hobby users over some 30+ years, you cannot do that with fake certificates. And it would be silly to risk a good name by suddenly switching to fake certificates.

Also consider there cannot be too much variation in the figures. Bigger than the specification is not possible, as it would make the item a reject (not sure what happens to rejects, they may sell them cheaper as noname rotary tables without a certificate?). And much smaller is not possible either due to the manufactoring process being all the same, and surface imperfections coming into play.

Finally, the company is making rotary tables at the very bottom end of the price scale, intended for hobby and low-tech use. They cannot be expected to invest in ultra precision metrology equipment and do their testing in a room airconditioned to +/-0.5 degrees. That would limit the resolution of the figures in the inspection records.

Originally Posted by Pete F

You cannot rotate a dial indicator around any type of centre or arbour in the TS and determine a height difference from that. The droop of the indicator and fixture will make the height appear off (indeed appear, surprise surprise, TS high). Side to side, yes no problem (albeit with care), but not top bottom.

I do it all the time. But I clamp my DTI directly into a spindle mounted chuck, to avoid any gravity droop. And I run the DTI tip directly on the inside of the tailstock taper, thus avoiding arbor imperfections. Taht is the setup I also use to return the TS after having it offset for taper turning.

The OP probably only had a DI at his disposal. I agree the setup he came up with has quite a big overhang from the spindle and may be somewhat affected by gravity. It would indeed make the TS seem high, maybe by 0.01 or 0.02mm.

Tested by Chris, inspected by Jack. Sounds fishy to me. Those stamps are just providing a name. There is no signature. Under our laws, that document would be worthless. It could be printed and stamped by anyone.

When I got my mill it came with a test certificate. The only thing I remember about it is that there was a very close similarity between the maximum allowed variation and the actual variation. At the time I remember laughing about this and passing the certificate off as "the Chinese way of doing business". A manufacturer who can balance right on that very tight line of "maximum allowable variation" is a fine manufacturer indeed. This allows for maximum use of tooling which saves money and gets the product to the customer as cheaply as possible. If one pushes hard to get perfection then one uses up more tooling. The other option is that we are getting the very bottom of the heap in quality, just slightly better than the stuff that does not meet spec at all. That poses the question, who gets "that" carp?

I am a little sceptical.

Dean