Here is a list of all the postings david bennett 8 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Chuck backplate error|
Ah, thanks for clarifying - I couldn't read that before . I was maybe hoping it was the elusive clearance!
Hmm, what do you read the 38.453mm dimension as (on the w20 nose) ?
Michael G, sorry to be so long responding. Those Schaublin nose specifications look interesting. Since the thread diameters are about 0.5mm larger than the register size, it looks like Schaublin doesn't belleve in close fitting backplate registers either.
|Thread: Another watchmakers lathe|
Hi Dells, have just seen better pics on NAWCC site. I still think its a flipover toolholder, but it sits on a WW lathe bed .I doubt it would fit an IME without some alterations.
The slide thingy might be a flipover toolholder for either/both boring or threading. Very useful for taking measurements without disturbing the settings. It sits on top of the compound slide.
Edited By david bennett 8 on 14/01/2021 16:08:36
|Thread: Chuck backplate error|
Anders Be, is that the tolerance on the diameter? what is the tolerance on run-out? what is the tolerance on thread/register runout? was the thread and register machined at the same setting in the machines own bearings? On a Schaublin it may well be so, but not on all hobby lathes. On myfords for example the register may well not be concentric to the thread. All the tolerances can combine to conspire against the user. If you have a recommended diameter to cut, how will you measure it? or will you cut-it and-try-it? If you are successful please carefully measure it and educate us all.
Edited By david bennett 8 on 12/01/2021 22:34:14
Edited By david bennett 8 on 12/01/2021 22:42:03
Back to the topic, I wonder how many people actually measure the bore of a backplate after making it a close fit to the radial register? I would not be surprised if it is considerably greater than those last few tenths achieved by cut-and-fit due to tolerances in manufacturing the spindle. Could some people actually measure bore/register figures from well fitting chucks and let us know?
This argument reminds me of arguments on religion - no-one will be convinced until they try it. For what its worth I intuitively believed that the radial (horizontal) register was important. What made me rethink this was not so was when I realised I was using an ML7 chuck on an ML4 with no collar. It repeated perfectly. Since then I have made many backplates for different lathes, so I could experiment. Experience has shown me that the close fitting spindle (horizontal )
register does nothing to aid repeatability, but can in fact interfere with a free running thread cut into a backplate with the shoulder (vertical register) cut at the same setting. I have made backplates for many Myford sized lathes (Wolf Jahn, Cataract, etc) but my interest is in smaller precision lathes such as Pultras, Unimat 3 and SL's and watchmakers lathes..On none of them do I bother to closely size thespindle (horizontal ) register. I will take expermental resuls over intuition ever time.
A loose fit is unlikely to produce a wobble. Dave.
The point re. a drunken thread is that is not possible to turn the vertical register true to the thread at the same setting. This is essential. The horizontal register is not important.
Chris, if your backplate goes on with a wobble it suggests your backplate thread is "drunken" This is very bad for repeatability.
Edited By david bennett 8 on 06/01/2021 18:39:50
|Thread: Meteror II Screw cutting lathe|
I understood from Tony's website only the Flexispeed Major had the hand finishing to the bed etc. I too would be astonished if it applied to the Meteor11
|Thread: Myford ML4 Restoration: Headstock bearings and spindle removal|
Luke, something you said there made me think the term "repeatable" may be being misunderstood. Do not expect that you can remove a piece of work from the chuck and then replace it and have it run true. Turn a piece of work true. Do not remove it from the chuck. Remove/refit the chuck with the work still clamped in the jaws, if it then runs true it is repeatable (apologies if you knew that)
Luke, thanks for clarifying that. All lathe noses have different errors. The whole purpose of the chuck backplate is to allow you to eliminate them . (Except the axial play - that is adjusted by the threaded collar at the rear end of the headstock ) For a full description of truing the backplate, see Tony's famous website "lathes.co.uk" the article "fit a new chuck"
Luke sorry, I put my edit (or within spec) in the wrong place Any slight error in the spindle vertical register will be eliminated when the backplate is trued on the lathe. The backplate should be absolutely true and repeatable,if nothing interferes with the fitting.
Edited By david bennett 8 on 16/05/2020 14:29:48
Luke, I am getting cofused here. I was under the impression that you had added a collar to your spindle to fit a new chuck. Do not cut anything from your original spindle. The horizontal register should be absolutely true. If it is indeed a collar that you have added, that too should be absolutely true (or within spec.) The chuck backplate is the loose plate that screws to the lathe nose, which should be trued before the chuck is bolted on. The register is simply the plain bore of the backplate. Can you measure the old chuck backplate bore that fitted to the original 1.125" horizontal spindle register.
Edited By david bennett 8 on 16/05/2020 13:18:54
Luke, as a matter of interest, would you measure the register clearance on your old ml4 backplate? ( mine has a 20 thou' clearance.)
Luke, I agree with Brian Wood's comments about where to measure the run-out . If the vertical register is true, then too snug a fit on the horizontal register can interfere with the self-centering action of the spindle threads. ( if carefully done, you might be able to see this with the aid of a little marking blue on the register)
Luke thanks in advance for your future efforts for science!.The ideal time to try this is when you
are trueing your new backplate to your lathe. When it is true,de-mount the backplate, then try to re-mount it off centre.Let us know if you can.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.