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  1. #1
    ghostdog662 is offline Aluminum
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    Default Best way to level a lathe

    Is there a relatively inexpensive way to level a lathe ? there are some inclinometers on ebay for under $50 but they only read the degrees in one tenth.

    Something like this is what I had in mind.

    LEVEL BOX DIGITAL ANGLE GAUGE INCLINOMETER PROTRACTOR 3 - eBay (item 180511337804 end time Jun-21-10 23:22:40 PDT)

    I know a standard level with a bubble isn't a super accurate way to do it that's why i am unsure.

  2. #2
    jim rozen is offline Diamond
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    1) what kind of lathe is this? Smart money says it's small, used. If a southbend then
    definitely used as they have not made those in a while.

    2) throw out any levels you own. Or sell them.

    3) use the money to buy a copy of "How to Run a Lathe" by south bend.

    4) follow the explicit instrucions therein on doing the "two-collar" test.

    It's all you need to set your machine up.

  3. #3
    CBM
    CBM is offline Plastic
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    Default

    Go to http://www.wswells.com/data/howto/H-3.pdf to see how the two collar test is done. Good Luck

  4. #4
    tentacles is offline Aluminum
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    Default

    Or... buy an inexpensive import level.. CDCO Machinery Corp.

    Not as good as a name brand unit but should be sufficient for levelling a lathe.

    Those guys also sell the QCTP holders for cheap.

  5. #5
    promacjoe is offline Hot Rolled
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    Quote Originally Posted by tentacles View Post
    Or... buy an inexpensive import level.. CDCO Machinery Corp.

    Not as good as a name brand unit but should be sufficient for levelling a lathe.

    Those guys also sell the QCTP holders for cheap.

    when I looked at the site, it looked kind of familiar, then I notice the address and phone number. It's the same as "totalcnctools.com". I wonder how many other Company names they run under.
    not that there's anything wrong with it.

    promacjoe

  6. #6
    Paula's Avatar
    Paula is offline Titanium
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    Quote Originally Posted by jim rozen View Post

    2) throw out any levels you own. Or sell them.

    3) use the money to buy a copy of "How to Run a Lathe" by south bend.

    4) follow the explicit instrucions therein on doing the "two-collar" test.
    Though I understand and appreciate the sentiment, I wouldn't actually throw out or sell my level. A precision level is useful for getting a machine (lathe, yes, but more especially a mill) level, both front-to-back and side-to-side. You might be surprised at how often this comes in handy when trying to align a workpiece on the machine when no other reference is available.

    Leveling a lathe for accuracy is a bit of a misleading concept. What one is actually trying to do is align the front and rear ways such that there is no "twist" which will cause tapered bores and O.D.'s when using a chuck. (Lathe beds are prone to this phenomenon due to their length, and the usual configuration of being fixed only at the ends.) A precision level can be placed across the top of the ways, front-to-rear, to check if the tops of the bedways are coplanar along their length (not necessarily "level"), and if not, adjusting the tailstock end of the bed to make them so. Whether this involves placing shims under the legs of a floor lathe, mounting feet of a bench lathe, or adjusting some kind of built-in mechanism, depends on the particular lathe in question.

    But wait! Often, it's not actually a twist, but uneven wear to the bedways which is having the same effect. In this case, using a level may not resolve the problem, depending on the location/extent of the wear. In either case, using a level to align the bedways should only be considered an initial step. Final adjustment should be performed based on the results of the Two-Collar Test:



    By using a bit of common sense, you can determine which way the tailstock end of the bed needs to be rotated. If the collar closest to the tailstock end is smaller than the headstock collar, then the bed needs to be rotated toward the front (CCW, viewed from the tailstock end), and vice versa.

    Once you've got the spindle aligned with the bed, then you can check the alignment of the centers, as the former affects the latter. Here's how HTRAL describes the procedure:




    Paula

  7. #7
    ghostdog662 is offline Aluminum
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    Default

    I bought a 8" machinist level and co-ax indicator. We'll see how it goes.

  8. #8
    Conrad Hoffman's Avatar
    Conrad Hoffman is offline Stainless
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    The bed needs to start out with no twist. That's what you use the level for. If the bed is straight, and the lathe turns a taper, either the bed is worn or the headstock is out of alignment with the bed. (assumes you use good measurement technique and aren't trying to turn a 1/4" shaft sticking 6" out of the chuck.)

    The "goodness" of the bed depends on the abuse and lack of oil its seen. The "goodness" of the headstock alignment varies between manufacturers and samples of individual lathes.

    If the bed is worn, live with it or get it reground. If the headstock is misaligned, scrape it, shim it, regrind it or otherwise get it pointed in the right direction.

    Once the taper is down to .0001-.0002 inches per inch, it's ok to tweak the bed slightly to correct it. If you try to fix the above problems by turning the bed into a pretzel, the carriage will no longer mate properly to the ways and you'll get instability and rapid wear of the carriage and bed.

    You need a level and it should be a pretty good one.

    CH

  9. #9
    moe1942 is offline Aluminum
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    Quote Originally Posted by jim rozen View Post
    1) what kind of lathe is this? Smart money says it's small, used. If a southbend then
    definitely used as they have not made those in a while.

    2) throw out any levels you own. Or sell them.

    3) use the money to buy a copy of "How to Run a Lathe" by south bend.

    4) follow the explicit instrucions therein on doing the "two-collar" test.

    It's all you need to set your machine up.

    Sanity at last...When I say this at other sites I'm considered a heretic..I just use a test bar after getting it close with a machinist level.

  10. #10
    PeteM is offline Diamond
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    Default

    I'm with the level-it-first crowd, based on personal experience with several lathes with not-too-worn-out beds. Just getting rid of twist in the bed has always gotten me close.

    One additional advantage, for bench lathes, is that the bench itself will invariably move a bit over time even if it is all steel construction. With a precision level, it's a couple minute job to tweak the lathe bed back to level condition any time precision is needed.

  11. #11
    jim rozen is offline Diamond
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    99 percent of all the machines discussed in this forum are used machines and will
    have worn (to some degree) beds.

    Simply slapping a good level on the tops of the V-ways really is just barely a start.

    It will read true but the machine will turn and bore taper. That's no good.

  12. #12
    Blob is offline Hot Rolled
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    Talking

    I just proved the validity of the above on my lathe (not that I doubted it). I had previously leveled it with a master precision level and I thought it was OK, but after reading this thread I decided to do the 2 collar test - it cut .0004" difference in diameters in 4 inches. A slight tweak on the leveling screw at the tailstock end, and it's now perfect. Way more perfect than I'll ever be! :-) Another one of the reasons I roam this forum!

  13. #13
    WestCoastFranky is offline Aluminum
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    A ha, so you know how to use the leveling screws! I've stared at mine for two years wondering how they work and which way I'm supposed to turn them to get the results I need. Please fill me in on how I'm supposed to use them.

  14. #14
    jim rozen is offline Diamond
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    There's a horrible secret here, and that is (no don't tell anyone!) that it's
    really tough to figure out from first principles which way to turn the levelling
    screws - and here of course, nothing is getting levelled, these are truly
    *twisting* screws - to get the error to diminish.

    Basically you try one one way, and see if the collar diameters converge. If they
    don't, that is, if they get farther apart - then you go the other way.

    I always have to write down the steps, such as, front screw in 1/6 turn, and rear
    screw out 1/6 turn, and put the collar dimensions down in the next column,
    to get it straight in my mind.

    Same thing with shimming legs on a machine with tailstock legs. Never can
    figure that out a priori.

  15. #15
    Blob is offline Hot Rolled
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    Quote Originally Posted by WestCoastFranky View Post
    A ha, so you know how to use the leveling screws! I've stared at mine for two years wondering how they work and which way I'm supposed to turn them to get the results I need. Please fill me in on how I'm supposed to use them.
    Tighten the leveling screw on the front (operator) side of the tailstock to rotate the bed counterclockwise as viewed from the tailstock end, and tighten the leveling screw on the back side to rotate the bed clockwise. I think this was explained in a previous post? You may (probably will) have to loosen the opposite side screw a bit when tightening them. For example if the collar nearest the tailstock is smaller than the one near the chuck, you need to rotate the bed counterclockwise at the tailstock end (tighten the operator side leveling screw) which will move the carriage and cutting tool away from the work at that end. I found that mine was close enough that just tightening the front screw without loosening the one on the back side was enough to get it into alignment. If you're close, which you should be before doing this, it won't take much to make a difference. You don't want to twist the bed unnecessarily to compensate for a grossly out of level condition. One thing to consider is that someone may have used the leveling screws previously, so you should loosen both of them before leveling the lathe, to remove any stress on the bed, and then after it's level, use the screws for fine adjustment. Hopefully I've explained it all right, and I haven't made any dumb mistakes! :-)

  16. #16
    DMF_TomB is offline Titanium
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    Default Digital Level what 0.1 degree is?

    0.1 degrees is about 0.100" per 57" or 0.010" per 6"

    0.020" per foot

    digital levels that read 2 decimal , 0.01 degree often vary 0.03 degrees and many are only rated to repeat 0.05 degrees

    Any good Field Machinist needs to calculate shims or leveling adjustment amounts and needs to be able to figure out what a level reading means per distance.

    A Starrett 98 red line level is 0.005" per ft per line increment and reading 1/5 of a line or 0.001" per ft is min reading possible and 0.020" per ft or 4 lines is normal max reading possible with a 8" level.

  17. #17
    jim rozen is offline Diamond
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    Any good used lathe owner needs to know that plunking a level down on the tips
    of the V-ways, and getting it to read just perfect all down the line,
    can still result in a lathe that turns and bores taper.

    No matter how good the level is.

  18. #18
    Blob is offline Hot Rolled
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    Quote Originally Posted by jim rozen View Post
    Any good used lathe owner needs to know that plunking a level down on the tips
    of the V-ways, and getting it to read just perfect all down the line,
    can still result in a lathe that turns and bores taper.

    No matter how good the level is.
    Yep! See my post above.

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