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  1. #46
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    Sep 2008
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    I have watched a video of someone taking the twist out of the bed and each shim made a difference to the dial gauges. When I tried the same exercise on the Nuttall I could not get the bed to twist at all. As I said, I would have to fiix the Headstock end firmly to the concrete and then pack and pull down on the high side at the tail end.
    If it is the bed twisting and, in my case the taper is decreasing towards the tail, does that mean that I have to lift up the side closest to the operator?
    With the amount of taper (0.435mm) that I am getting over 220mm can I assume that I would be getting something like 2mm over the 40" bed?
    The test bar is straight.
    Can you tell me the order that all of these measurement checks should proceed. I'm presuming that checking the level is No. 1
    1. Check level
    2. ?
    3. ?
    4. ?

  2. #47
    Join Date
    Jul 2008
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    near Warragul, Victoria
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    Video of a Nuttall ..seems to run quietly

    https://www.youtube.com/watch?v=trFshVjTddc

    I don't think you can fix the problem easily with shims

  3. #48
    Join Date
    Apr 2008
    Location
    NSW
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    The hardest thing to level is something that has little flex but is twisted . So it may need to be bolted down to remove that.
    I have my lathe on 6 large foot pads and not bolted down. It works because the bed has some flex so all the feet bare some weight but it levels .
    A lathe sitting out of level for years may take a set even one as rigid as a Nuttall .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  4. #49
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    Sep 2008
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    Thanks to everyone for listening to me. I'm sure you all have other, more important things, to attend to. I want you all to know though, that I do appreciate your time and patience.
    I will spend a bit of time on the bed levelness(?) If I could only get it to twist, I would know which way it needed to go (if it does).

    "If it is the bed twisting and, in my case the taper is decreasing towards the tail, does that mean that I have to lift up the side closest to the operator?" At the tail end.

  5. #50
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    Oct 2011
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    Norwood-ish, Adelaide
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    To visualise what is happening, think in exaggerated terms.
    In your case as the part is getting smaller at the tail stock end (making a cone) , if you were making that on a 'perfect' machine, you would have to wind the tool in. Think how you would have to twist the bed to get the same thing (then think of the correction).
    My visualised fix is that the tailstock foot furthest away needs to be lifted to reverse the twist.

    Michael

  6. #51
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    Jan 2011
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    He is now turning a bar at 2 points now so it should be concentric.

    Dean

  7. #52
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    Jan 2011
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    Quote Originally Posted by Michael G View Post
    To visualise what is happening, think in exaggerated terms.
    In your case as the part is getting smaller at the tail stock end (making a cone) , if you were making that on a 'perfect' machine, you would have to wind the tool in. Think how you would have to twist the bed to get the same thing (then think of the correction).
    My visualised fix is that the tailstock foot furthest away needs to be lifted to reverse the twist.

    Michael
    Yes. That is what I said earlier. I am glad you concur Michael. I can't find a wipe the forehead smiley.

    Dean

  8. #53
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    Sep 2008
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    Sydney
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    DSC_0871.jpgBack again!
    In the absence of a precision machinist level I came across this method, on YouTube.
    While it doesn't tell me the overall lathe levelness it does a very good job of checking for any twist in the bed. So, the first reading near the chuck was marked at 0. The reading at the other end of the bed showed the plumb bob slightly away from the 0, closer to the back. I then placed a 0.1mm feeler gauge under the rear side and this moved the plumb bob back to the zero. I tried a 0.15mm shim but this was too much.
    The place where I took the readings from was the flats. Which is what the handbook says.
    I also took readings off the top of the V's and could not read any twist at all.
    Is 0.1mm good news?
    I took the same readings with a piece of 1/4" plate under the far side tailstock end foot but the readings did not change.
    Slim

  9. #54
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    Sep 2008
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    DSC_0854.jpgDSC_0857.jpgDSC_0862.jpgDSC_0868.jpg
    1st pic is near the chuck, plumb bob on the zero.
    2nd pic is 40" down the bed.
    3rd pic is with 0.1mm shim under
    4th pic is with 0.15mm shim
    Slim

  10. #55
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    Aug 2008
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    near Rockhampton
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    On a lathe that old and especially a Nuttall which had soft beds, wouldn't the bed be worn and thus make any exercise in trying to measure twist futile?
    Gold, the colour of choice for the discerning person.

  11. #56
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    Sep 2008
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    You could be right but is 0.1mm a big issue, from end to end. I sort of get the feeling that it's never going to be perfect. I just want to get it as close as possible.
    Slim

  12. #57
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    Take the chuck off and see if you can get onto the unworn section right against the headstock, if there is any. The tailstock end where you have it should be good.

    Dean

  13. #58
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    Aug 2010
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    Quote Originally Posted by .RC. View Post
    On a lathe that old and especially a Nuttall which had soft beds, wouldn't the bed be worn and thus make any exercise in trying to measure twist futile?
    I'm a little surprised that the whole procedure hasn't had a lot more input from the usual suspects, perhaps they're tired of going over the same arguments with each other over and over.

    I expected to start reading comments directly after mention was made of using a piece of bright bar to check runout, given the (lack of) tolerance in off the shelf bright bar... unless the HT bar is much more accurate than I give it credit for?

    No disrespect intended to those who ARE in this thread and helping as best they can, but from previous discussions on here (not that I'm exactly experienced in this) aren't we're starting in the middle here? There seems to have been very little discussion on more basic checks, where I'm sure on previous threads there has been a whole procedure laid out to work through from start to finish?

    A few things that come to mind.

    Could just be the photo creating an illusion, but in the shot with the bar with the two measurements on it, it looks like the gap isn't quite sitting down flush with the rest of the ways? If the gap isn't seated properly, I'd imagine that would have an effect on the diameter closer to the chuck... Likewise, are there any dings on the rest of the ways? Are the chuck and spindle mating faces free of dings and swarf?

    If the jaws on the 3 jaw chuck have now been ground, but the lathe is potentially turning a taper, hasn't that taper now been transferred to the chuck jaws? While not relevant currently to the measurements on the bar, I'd imagine if the lathe is indeed turning tapered, the 3 jaw should be reground again once this has been corrected?

    Are the gibs adjusted correctly? If so, are there any tighter/looser spots in the carriage travel (which would likely indicate, as .RC. suggested, wear in the bed).

    How did you check for play in the spindle bearings exactly? My inclination would be to set a dial indicator up on top of a piece of bar sticking out of the chuck, then attempt to lift the bar by hand, and see how much the indicator moves. I'm sure it's not the best method, but without going back through a number of old threads on this stuff, best I can come up with.

    Just a few of the more basic thoughts that I would personally start with, before I even moved to bed twist and test bars and cuts. I'm sure there are some others that could be done before moving to actually adjust something, but again, I'd have to go digging back through a bunch of old topics to find those discussions.

  14. #59
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    Maybe you could do the test again but this time use a length of aluminium bar instead of the steel bar. And a sharp tool.

  15. #60
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    Does it matter if the test bar is not accurate to start with? Isn't it turned down to test?
    The gap is flush with the rest of the ways which appear to be in good condition with no dings etc.
    I realise that once the taper thing is sorted out I will have to regrind the 3 jaw. They were slightly bell mouthed and the first grinding did fix that.
    The carriage seems to run smoothly along the entire bed.
    I will check the spindle play as you have suggested.
    Is there a way to test for taper without using a chuck? ie.Taking the chuck out of the equation.
    Thanks all
    Slim

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