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Thread: Lathe alignment

  1. #1
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    Default Lathe alignment

    Trying to get my Takisawa lathe aligned a bit better.

    Using a Starrett 98 level, I’ve got the bed nice and level across the ways from to back.
    It’s slightly down at the headstock end, but I’m not too fussed about that.
    If I put a piece of ground bar in the chuck and put the level on top it matches the bed - slightly down at the headstock end.

    All good so far

    If I mount an indicator on the cross slide and sweep the ground bar end to end it’s close to perfect - about .01mm difference over 300mm.

    If I sweep the side of the bar it’s about 0.10mm difference.
    Towards the rear of the lathe at the chuck end.
    There’s a slight bit of runout in the 3 jaw chuck do I rotate the chuck to different spots. Consistent 0.1mm from one end to the other.

    I put a piece of ~40mm bar in the chuck and take a couple of cuts at the same cross slide setting.
    Definitely tapered - larger at the chuck end which matches what the indicator and ground bar showed.

    To me it points towards the headstock being out of alignment with the bed - needing the chuck end moved towards the rear.
    Thought I’d best get a reality check on that conclusion before I start messing with it.

    Anything I’m missing??

    Steve

  2. #2
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    Default Lathe alignment

    Sounds like the tailstock is shifted towards the front of the lathe.

    Can you not realign the tailstock 0.05mm towards the back of the lathe?

  3. #3
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    Quote Originally Posted by neevo View Post
    Sounds like the tailstock is shifted towards the front of the lathe.

    Can you not realign the tailstock 0.05mm towards the back of the lathe?
    Tailstock isn't involved.

    Steve

  4. #4
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    Default Lathe alignment

    Quote Originally Posted by OxxAndBert View Post
    Tailstock isn't involved.

    Steve
    Is it just test bar in chuck? I was struggling to understand conceptually. But if tailstock is not being used then I’d agree, sounds like the spindle isn’t parallel to the bed.

    Clearly above my level of expertise. You’ve already factored in bed levelling.

  5. #5
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    LOL - clearly above my level of expertise too!

    Yes - just a test bar in the chuck.
    I frigged around the other night with the tailstock as I had some decent taper on a part I was turning between centers.
    Got to the point where I was chasing my tail a bit so thought I'd better start with the basic alignment. I've leveled the bed before but never gone the fully distance and checked the accuracy.

    Steve

  6. #6
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    Hence why I just make small parts that don’t need to be accurate Lathe alignment

  7. #7
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    OxxAndBert

    Try a 4 jaw chuck, if you have one. Zero your test bar & check if the run out changes.

    JohnQ

  8. #8
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    Hi Steve, Guys, Won't wear or slop on the saddle cause that problem ? Getting bigger at the chuck end is what I would expect under those conditions. Does the figures change if you tighten the gibs ?
    Best Regards:
    Baron J.

  9. #9
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    A "2 collar test" would be a more reliable way to check it. Is the headstock adjustable on the bed?

  10. #10
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    Default

    seems like a headstock alignment issue to me. Is the headstock adjustable on that lathe? or is it mounted to vee's.
    If i was doing that test i would put my bar in a 4jaw chuck and dial all of the runout from it, best to eliminate as many possible errors as you can.

  11. #11
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    Thanks guys.

    I’d expect that wear would tend to be worse a few inches away from the chuck and would tend to allow movement of the saddle towards the operator, and downwards.
    Since the sweep along the top of the test bar is good, to me that indicates there’s not much vertical wear, but maybe that’s not a valid assumption.

    I’m starting to overthink it so will throw on the 4 jaw chuck and some longer bar and see what it’s like further away from the chuck in case it’s just something weird going on there.

    The headstock sits on a flat mount surface and is adjustable. Not sure what it pivots on at the chuck end but the manual just talks about loosening the clamp bolts and using these adjusting bolts at the change gear end.



    Steve

  12. #12
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    That looks similar to mine. It took me a bit of faffing around with indicators & trial cuts but it's now perfect.

  13. #13
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    Those bolts look like the solution surely? If you tweak them it looks like it would adjust the angle of the spindle vs the bed?

  14. #14
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    Isn't the common way of aligning the spindle axis with the ways to adjust it out using the levelling feet (or shims)?
    Thereby inducing a slight twist in the bed. At the end of the day, it doesn't really matter if the lathe bed is dead level or not. What matters is that the spindle axis is parallel with the bed in the vertical and horizontal planes. Or is this only done on small lathes? It's certainly how Hercus recommends doing it.

    Steve,
    I wouldn't be adjusting the headstock until I'd tried adjusting/shimming the feet.
    Chris

  15. #15
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    Thanks Chris. Adjusting the feet was the first thing I tried.
    I can pretty much jack the intermediate feet off the ground by adjusting one of the headstock end corners without seeing any significant change on an indicator against the side of the test bar. The lathe construction is pretty solid - headstock/bed are bolted to a monolithic casting comprising the headstock pedestal, chip pan and tailstock end pedestals - so I'm not surprised that it doesn't move much.

    I faffed around a bit more with it last night. Fitted the 4 jaw chuck, got inconsistent results, then finally realised that the chuck is probably classified as "pretty flogged" condition with quite a lot of play between the jaws and the body. Particularly at the smaller diameter.

    Put the 3 jaw back on (which is "tight as bro"), much more consistent results - same as what I got earlier - but even though its set up as a "knock-tru" chuck I couldn't get the bar running perfectly concentric at both ends so either the bar or the chuck is out of whack.

    At that point I decided to cut my losses, be aware that the headstock is likely slightly out of alignment and just work around it.
    I'll come back to it at some point when I've got more time.
    Probably the bigger issue is the worn 4-jaw, and that might help explain some of the random weird behaviour I've had on occasions with chatter and jobs walking in the chuck etc when using it. I should have picked it up before now.
    Anyone got a great condition 10" D1-6 4 jaw chuck lying around gathering dust

    Steve

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