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Thread: lathe levelling

  1. #16
    Join Date
    Jul 2010
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    Melbourne
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    Well sort of, more like "all other errors can be hidden* by tweaking tailstock alignment"

    Stuart

    *pretty much.... depends the exact error and how well you're going to measure things.

  2. #17
    Join Date
    Jul 2012
    Location
    Griffith NSW
    Posts
    435

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    You can use tailstock alignment to correct for a twisted bed, but only in the one location of the tailstock. if you move the tailstock towards the spindle, the correction would gradually approach zero. If you move the tailstock away, it would require more offset to account for the twisted bed. This is why you level the lathe without reference to turning between centres or the tailstock in any way. A level bed means that a correct tailstock is correct at all points.

  3. #18
    Join Date
    Aug 2007
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    Melbourne
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    Quote Originally Posted by morrisman View Post
    Yes , its just my backwards methods, doing it the hard way I am trying to tweak the Sheraton to a good accurate standard , by doing this I hopefully will learn about the ins and outs of lathes . Sometimes an anomaly comes along that doesnt add up . Its all part of the mysteries of machining . Mike
    Mike,

    I highly recommend you get hold of Prof. Georg Schlesinger's book "Testing Machine Tools". Free PDF versions of older issues are floating around (just ask if you cannot get your hands on). There look up under the section "test chart for finish lathes up to 400mm cener height". You got to do these in the sequence they are described there, because some alignments are a prequisition for following alignments.

    Maybe you still have a copy of the inspection record for your specific lathe. Or you can find one for your make/model lathe. Or failing that, you can also take just any generic lathe inspection record. These are invariably and always based on the above work of Prof. Schlesinger, just more compact (the whole book in one page). Again you need to follow STEP BY STEP the tests/alignments of the inspection record. If you do it in reverse order, you will NEVER - EVER get anywhere. Checking the bed level is usually step 1, headstock alignment is step 8, parallel turning between centers and for work held in chuck is step 14, facing concave is very last.

    Now you may skip step 1 (bed level), but only IF you never disturbed the headstock to bed alignment, and you feel confident no previous owner did so, and your lathe never had a major transport accident.

  4. #19
    Join Date
    Jul 2008
    Location
    near Warragul, Victoria
    Posts
    3,718

    Default YEP

    Quote Originally Posted by cba_melbourne View Post
    Mike,

    I highly recommend you get hold of Prof. Georg Schlesinger's book "Testing Machine Tools". Free PDF versions of older issues are floating around (just ask if you cannot get your hands on). There look up under the section "test chart for finish lathes up to 400mm cener height". You got to do these in the sequence they are described there, because some alignments are a prequisition for following alignments.

    Maybe you still have a copy of the inspection record for your specific lathe. Or you can find one for your make/model lathe. Or failing that, you can also take just any generic lathe inspection record. These are invariably and always based on the above work of Prof. Schlesinger, just more compact (the whole book in one page). Again you need to follow STEP BY STEP the tests/alignments of the inspection record. If you do it in reverse order, you will NEVER - EVER get anywhere. Checking the bed level is usually step 1, headstock alignment is step 8, parallel turning between centers and for work held in chuck is step 14, facing concave is very last.

    Now you may skip step 1 (bed level), but only IF you never disturbed the headstock to bed alignment, and you feel confident no previous owner did so, and your lathe never had a major transport accident.
    That is good advice . I do have a copy of "Testing Machine Tools " Somebody onthis forum posted a link to the pdf version and I had it printed and wire bound in town. Trouble is, I have aquired quite a library of machining books and itis too easy for me to miss reading the more important texts as I have so manytoo choose from ! Mike

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