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  1. #1
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    Default 10K levelling screws

    I've managed to uncover the leveling screws at the tailstock end of my lathe.
    The whole thing is glued up with many layers of paint. I understand you loosen one screw and tighten the other. Does this raise one side wrt tother? ie induce twist? What does the internal levelling mechanism look like? - I haven't found any diagrams. Do I need to unlock any other screws/bolts first? Looking down between ways, there are 4 suspicious looking holes in the top of the foot casting - are there screws in the bottom of these? Mine are full of years of crud and not easy to clean out.
    thanks!

  2. #2
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    Quote Originally Posted by Anatol View Post
    - I haven't found any diagrams. ...
    The bed is mounted via a pin that goes left/right, you can see the ends if the paint's not too thick. The bottom of the bed has a sort of vertical fin sticking down, and the two screws bear on it from opposite sides. You slack one and tighten the other until the two collars on your test piece mike the same.

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    Great thankyou
    can you unpack "the two collars on your test piece"?
    thx
    A

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    You need to turn a test bar unsupported by the tailstock to dial in the bed adjustment screws. I think there is a description in the south bend book, How to Run a Lathe. There are a bunch of videos on YouTube as well.

    Basically it’s a piece of round stock ~8” long with the center and ends relieved. You end up with two short sections (collars) about 6” apart with a slightly larger diameter. You turn both collars unsupported by the tailstock without adjusting cross or compound settings. Measure the diameters and adjust the bed screws to remove the taper. Once the bed is dialed in, turn the same bar between centers and align the tailstock.

    Relieving the center section saves cutting 6” of stock. Cutting two 1/2” wide collars is quicker and less prone to chatter.

    Hope this helps

    Ben

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    Yes, sorry - two collar test as in how to run a lathe book. Step one, remove tailstock from machine, do not use it for this test. it's tough to determine in advance which screw gets tightened. If the two collars diverge in size, you went the wrong way....

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    "You need to turn a test bar unsupported by the tailstock to dial in the bed adjustment screws. "

    you mean turn in the sense of rotate?
    the test bar needs to be made on a lathe that is already square and level, or its no good, right?

    oh, I guess if it is a store-bought ground bar... it'd be straight...
    so why turn down the bar, wouldn't a straight bar be just as good?
    (I look in the book...

    ...so you're effectively lifting or lowering the tail end wrt to the spindle end, in order to get the tool to run along the horizontal centerline of the work...

    So the 'leveling' screws then don't adjust for longitudinal twist in the ways...

    I have a precision level , so I guess Id use that across the ways at both ends to check for twist, then ...shim?

    Why is 'level' so important - surely if the axis of the spindle is parallel to the plane of the ways, its good, even if the whole machine is at 5deg off horizontal?

    Sorry to persist here, I'm trying to understand all the errors one could make.
    I really want to get my lathe as rigid, square, straight and level as I can.
    thx!

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    You turn (as in machine) the test bar on your lathe. The leveling screws in the tailstock foot twist the bed so you don’t need shims.

    Leveling with a precision level gets you really close. The bed doesn’t need to be level just not twisted. So both ends out of level the same amount is fine, A slant bed cnc lathe is an extreme example.

    This video explains it better than I can. There are others out there as well. Where they talk about shimming the bed to remove twist, you will use the screws.
    How To Align Your Lathe - YouTube

    Hope this helps

    Ben

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    "The leveling screws in the tailstock foot twist the bed"

    Ah, so they're not really 'levelling' but 'untwisting'
    cool
    thanks for the vid link. blondihacks is great
    A

  12. #9
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    1) remove tailstock from machine for this.

    2) put that level back in its box and put it alongside the tailstock. Not needed for this.


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