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  1. #61
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    Maybe I'm missing something but I don't quite get the need for an accurate test bar before you start.
    Is that just for static testing?
    Is the aluminium for ease of cutting? It would have to be a decent dia not to deflect? What size?

  2. #62
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    I'm a little surprised that the whole procedure hasn't had a lot more input from the usual suspects,
    My thought too.

    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?
    Good. Someone I can blame for the mistakes. Some previous threads would be a useful read, but my attempts at finding threads on here are usually woefully off the mark.

    Does it matter if the test bar is not accurate to start with? Isn't it turned down to test?
    Maybe I'm missing something but I don't quite get the need for an accurate test bar before you start.
    If you machine the bar as I have said it does not matter what it is like before you start. The important thing is to do a light continuous cut all the way along so both sections are as close to the same as possible and that the bar is tight in the chuck and large enough not to flex.

    Is that just for static testing?
    Yes

    Is the aluminium for ease of cutting? It would have to be a decent dia not to deflect? What size?
    Yes. That is the idea. Just use a sharp HSS tool.

    Is there a way to test for taper without using a chuck? ie.Taking the chuck out of the equation.
    No. If you do the machining as above then the bar will be running concentric with the spindle. This is the only way to acheive this with certainty.

    Dean

  3. #63
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    Quote Originally Posted by slim View Post
    Does it matter if the test bar is not accurate to start with? Isn't it turned down to test?
    It doesn't once you start turning, but I got the impression from the earlier posts that to start off with, you were simply using a dial indicator on the bar as it was? Round bar stock is not necessarily perfectly round.

    Quote Originally Posted by slim View Post
    The carriage seems to run smoothly along the entire bed.
    But are the gibs adjusted up?

    Quote Originally Posted by slim View Post
    Is there a way to test for taper without using a chuck? ie.Taking the chuck out of the equation.
    Hmmmm... Not sure if I'm imagining this, but I THINK its possible to buy precision ground test bars with various tapers on the end? Which would then insert directly into your spindle (I assume there's a taper inside a Nuttall spindle!). *edit* yes, you can, the first thread linked below should entertain you on that topic ...

    As you're working out, lathe alignments are a bit of a rabbit hole... There have been some fairly detailed discussions on these forums in the past about aligning lathes, unfortunately it will take a bit of time reading to catch up on which are which, and find a straightforward procedure for assessing and adjusting the condition of a secondhand lathe.
    Below is a nice one to get you warmed up, some of the 'banter' might give a clue as to why you haven't got a lot of interest in your thread over the couple of weeks its been running....

    //metalworkforums.com/f65/t1965...-alignment-bar

    Some more discussions here (headstock again, just the first two I came up with):

    //metalworkforums.com/f65/t192493-lathe-alignment

    And here's (hopefully) a link to Google with some search results for this forum, reading through some of the results that mention taper, twist, wear should yield some good information...

    https://www.google.com.au/search?q=l...uMH-nc8wez54g4

  4. #64
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    But are the gibs adjusted up?
    What gibs are you talking about? I have never seen gibs on any lathe in relation to the carriage. The carriage runs on a vee.

    Dean

  5. #65
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    Quote Originally Posted by Oldneweng View Post
    My thought too.



    Probably more a case of where do you start?

    A brand new three jaw usually has holding tolerances of 0.1mm eccentricity.

    A four jaw will probably not hold stock parallel with the spindle (hence why the OP found his bar snaking all over the place)

    If the lathe is worn, how would you even measure twist, as you are not going to know. You can put a deliberate twist in to try to compensate for wear, but it is something that will create other issues. Many people forget about the tailstock holding alignment.

    If the OP really does not use the tailstock, but does all chuck work, then you might as well just align the headstock to the worn bed, so it turns reasonably parallel.
    Gold, the colour of choice for the discerning person.

  6. #66
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    Quote Originally Posted by Oldneweng View Post
    What gibs are you talking about? I have never seen gibs on any lathe in relation to the carriage. The carriage runs on a vee.

    Dean
    http://cdn1.grizzly.com/manuals/g0750g_m.pdf

    Page 72 shows the adjustments for the carriage (saddle) gibs on my chinese lathe. I was under the impression all lathes would run them, rather than relying on gravity alone to stop one side of the carriage lifting during cuts?

  7. #67
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    Quote Originally Posted by .RC. View Post
    Probably more a case of where do you start?

    A brand new three jaw usually has holding tolerances of 0.1mm eccentricity.

    A four jaw will probably not hold stock parallel with the spindle (hence why the OP found his bar snaking all over the place)

    If the lathe is worn, how would you even measure twist, as you are not going to know. You can put a deliberate twist in to try to compensate for wear, but it is something that will create other issues. Many people forget about the tailstock holding alignment.

    If the OP really does not use the tailstock, but does all chuck work, then you might as well just align the headstock to the worn bed, so it turns reasonably parallel.
    That was kind of my point, on an old lathe with unknown provenance, I thought there had previously been discussed a sequence to follow which involved assessing and quantifying issues of wear (and adjusting as far as possible), before moving towards aligning it as best as the wear discovered in the previous step would allow.... All of your points are the type of thing I was meaning when i mentioned a lack of basics - particularly relevant in this context is your point about the 4 jaw not necessarily being parallel to the spindle, as its the results from this test that are being used currently as a basis for twisting the bed. My comments about burrs on the chuck mating face and checking spindle bearings were aimed in a similar direction.

    Make no mistake, I have no problem with aligning things as needed - however, how it has been determined that whichever particular alignment is needed is where the problem lies. Is the alignment in question the sole factor involved in the inaccuracy being chased, or is there wear/operator error/damage/another alignment etc that could factor into it? Personally, I would want to make damn sure that whatever I was aligning was the answer to my problem, before ending chasing my tail.

    Not much point in trying to twist the bed to get two collars the same at 250 mm apart with one next to the chuck, if the lathe has only ever done workpieces at 100mm long, and has a bloody great ditch worn into the ways up near the chuck - it's simply not going to help. However, if that turns out to be the case, armed with that knowledge you could potentially check that the unworn section of bed isn't twisted, and attempt to set up longer jobs there, so that the carriage doesn't drop into the hole...

  8. #68
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    This video I took a few years ago shows the folly of trusting even new chucks.
    Attached Files Attached Files
    Gold, the colour of choice for the discerning person.

  9. #69
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    Quote Originally Posted by Jekyll and Hyde View Post
    http://cdn1.grizzly.com/manuals/g0750g_m.pdf

    Page 72 shows the adjustments for the carriage (saddle) gibs on my chinese lathe. I was under the impression all lathes would run them, rather than relying on gravity alone to stop one side of the carriage lifting during cuts?
    Ok, page 73 mentions saddle side gibs, but I would not have called them gibs. Lots of lathes have these and I did mention them before. They only hold the saddle down and do not affect the movement of the carriage like the gibs in the cross slide or compound do unless it is a flat bed lathe.

    Richard we are just saying not to play with the headstock alignment until other issues have been checked out.

    Dean

  10. #70
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    DSC_0881.jpg
    I now have a 0.05mm taper over the 250mm as opposed to original taper of 0.435mm.
    As you can see the taper is now running back to the chuck.
    I spoke to someone who has had a couple of these Nuttall lathes.
    He suggested to try the headstock alignment as he had done and that it might need a couple of goes. He was right. I did it twice. the first time I went the wrong way (it was getting late) Second time, the result is in the picture. I'm pretty sure that I could get the 0.05mm out, if I adjusted again. But do I need to? Even though it's a fairly easy operation.(on this machine)
    Once again I thank you all for the help you have given. In the last couple of weeks my "lathe awareness" along with my "lathe vocabulary" has been vastly improved and that can only be a good thing. I have also learnt that most of time you just have to have a go. (safely)
    Slim

  11. #71
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    Now you have to check cross slide perpendicularity.
    Gold, the colour of choice for the discerning person.

  12. #72
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    (Now you have to check cross slide perpendicularity.)

    Ok, so whats the best way to check that?
    and, is my headstock adjustment to 0.015mm acceptable?

    (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.)
    I did this test and could not record any movement in the spindle
    slim

  13. #73
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    DSC_0887.jpg
    Well, good news I think. I made one more headstock adjustment and am now cutting the 2 collars the same. Yippee! 43.175mm both ends.
    Now I am not sure if this is the correct method but I left a small point on the end of the test bar to check the tailstock and, guess what, it appears to be spot on centre now.
    Apart from now regrinding the jaws in the 3 jaw, what else should I do?
    Slim

  14. #74
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    Quote Originally Posted by slim View Post
    (Now you have to check cross slide perpendicularity.)

    Ok, so whats the best way to check that?
    and, is my headstock adjustment to 0.015mm acceptable?

    (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.)
    I did this test and could not record any movement in the spindle
    slim
    Not that easy to check cross slide perpendicularity. I would not bother as there is nothing you will be able to change it anyway. Other then move the headstock.

    If you are getting a good surface finish, then the spindle bearings are fine.

    Your tailstock might "look" to be spot on, but I know it won't be, but it will probably be good enough for your needs. I used to own a Nuttall like yours and it was worn a lot more then yours is and it still did what I wanted up to a point.
    Gold, the colour of choice for the discerning person.

  15. #75
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    Slim Turn a piece of short bar to a 60 degree point i.e. in your chuck , the top slide is set to 60 degrees for this job. You have now made a concentric centre at the headstock . If you have a accurate ground bar with centres each end, use the bar between the headstock centre you made and the tailstock centre , run the dial gauge along the test bar and adjust the tailstock until the dial gauge shows minimal movement .

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