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  • academic lathe question

    When my new lathe or second hand lathe was being set up I took great pains to make sure my newest expensive aquisition was level.But why????? I have wondered ever since why it needs to be level.For example if it tilted towards you, or away, or up one side ,or down the other, what would happen?whan we can have vertical lathes why should it make any difference?I feel sure there is a reason but I have pondered the problem and it seems to me that the lathe should work fine obviously it will not but why?????.Alistair
    Please excuse my typing as I have a form of parkinsons disease

  • #2
    A lathe does NOT!!! need to be level. But, if it's not level, it needs to not level consistently, so the bed is not twisted. Since it's typically more difficult to measure consistent not-level than it is to measure consistent level, the usual thing is to level the lathe bed.

    Leveling is merely a convenient means to an end -- getting the lathe set up so the bed is not twisted.

    Even when a lathe *is* level, the final test is always turning a test bar, to be sure the lathe does in fact turn parallel.
    ----------
    Try to make a living, not a killing. -- Utah Phillips
    Don't believe everything you know. -- Bumper sticker
    Everybody is ignorant, only on different subjects. -- Will Rogers
    There are lots of people who mistake their imagination for their memory. - Josh Billings
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    • #3
      in the case of a smart and brown 1024...you could probably stand it on a pile of rubble and it wouldn't distort ...it's too heavily built .

      all the best..mark

      Comment


      • #4
        Warping a Possibility?

        I was always told that the leveling was done to prevent warping of the lathe bed or other parts of the lathe. I too, have wondered about it as warping a lathe bed is like twisting an I-beam. There isn't much twisting going to take place until you get some very sizeable loads and I don't think the loads produced by turning items will cause warping of the bed. Maybe if you have a 12 or 16 inch swing lathe you can generate large loads to cause problems but with smaller ones, I don't see much of a problem. But, then again, the loads would be generated whether the bed was level or not. So the warping could take place if it was leveled or not.

        I have my lathe mounted on heavy duty casters so that I can move it. My shop layout is such that I have to move the lathe about a foot to work on the mill. The lathe sits on a wooden frame which has the casters mount on its bottom. So far, I have not encountered any problems with the lathe being mounted as I have it. Vibrations have not been a problem as when I start to get any vibrations, I modify what I'm doing so that they are eliminated.

        Bill
        Bill

        Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

        Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

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        • #5
          Bill-- its not about any likelyhood of putting in some sort of permanent warp, but rather about working with a bed that is twisted in use. Everything moves. Heavy machine tools have lots of weight to attempt to pull things out of square. One of the many things I have learned from scraping in my mill is that you have to take into account the force that the weight of a machine tool sub assembly will have on itself. For example, you scrape in a Bridgeport knee ways a bit high at the nose because 300 pounds of table and saddle plus another maybe 90-100 for the vise will flex the knee downward. It may seem big and rigid...but everything moves under force and even under its own weight.

          There probably is some ratio of rigidity to weight under which twisting is a non-issue. My 7x14 mini lathe is pretty rigid for it diminutive length, but a bigger heavier longer lathe set on an uneven floor (they are all uneven) could easily end up less than square. Since the carriage follows the tracks that are the lathe bed, twisted ways make for less than true parts.

          SGW hit the nail on the head....if you had an easy way to verify that you had an unstressed (and therefore planar) lathe bed other than using "level" as the standard, that would be perfectly acceptable.

          Paul
          Paul Carpenter
          Mapleton, IL

          Comment


          • #6
            When bolting a benchtop lathe down it will track the surface you're bolting it to and be warped/twisted accordingly. Mine's shimmed to within .0005 of being flat as measured with a Machinist Level across the tops of the V's.

            Level to the ground isn't necessary and just about impossible anyway.

            SP

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            • #7
              Remember Alistair my old mate, Confusius he say, Man who f#~k's women on hillside, him not on level.


              .
              .

              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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              • #8
                But why????? I have wondered ever since why it needs to be level.
                THAT OLD GANG 'O MINE

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                • #9
                  LeBlond "Port-a-lathe"....

                  Weren't some of these things supplied to the US Navy ? For shipbaord use ??? Imagine using or moving one in action or underway in heavier seas. I wouldn't want to get in it's way in a cramped alleyway....Lucky thing ships have lots of expendable crew. "Damage Control !!!"
                  Level that one.
                  Rick

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                  • #10
                    A buddy of mine ran a lathe in a drilling company's machine shop when he first got out of school. The bed ways were 12 feet long, and the head and tail ends were securely bolted to two separate slabs of the concrete floor.
                    Tapered like a S.O.B. in the summer, and it the winter it tapered just as bad, but in the opposite direction.

                    Level? Sure it was! As for straight, not even close.

                    Hey, if it was easy it wouldn't take a craftsman to make good parts...

                    Rick
                    Home Model Engine Machinist

                    Comment


                    • #11
                      Setting a machine "level"

                      Originally posted by pntrbl
                      When bolting a benchtop lathe down it will track the surface you're bolting it to and be warped/twisted accordingly. Mine's shimmed to within .0005 of being flat as measured with a Machinist Level across the tops of the V's.

                      Level to the ground isn't necessary and just about impossible anyway.

                      SP
                      Right on SP.

                      The idea is to get the lathe/machine beds both in an unstressed and co-planar state. The end requirement is to achieve a "no stress/"twist"" state with everything in the same straight plane. Level, as is horizontal might be nice but its not essential. I'd guess my lathe and mill are out of "level" anywhere between 10 and 50mm - but they work well and I'm not fussed.

                      I suspect that the "true horizontal with precision level" bit while ideal and probably correct is a hang-over from prescriptive "Rules" that enshrined "traditional methods" that "worked". In other words, if you did as told all would be OK. Not knowing why was not required. And it kept some people in a job and on a nice little earner and with a bit more "status".

                      In my experience all precision machines such as Tool-room grinders and the like are on 3 legs, none of which are fastened down at all - just packed or adjusted and reliant on their own weight.

                      The main requirements of a lathe alignment for general purposes are that:
                      - the bed is straight and not twisted or stressed - pack under the pads/supports so that there is no space/gap under any of them - this can be critical;
                      - the head-stock spindle axis is parallel to the lathe bed in the "vertical" plane and parallel to the guides in the "horizontal plane"; and
                      - the tail-stock centre/axis is similarly aligned and at the same centre height as the head-stock spindle.

                      Testing for "true" in/of a head-stock spindle is in 2 parts:
                      1.
                      test the headstock alignment to the bed ways: turn short test piece in a chuck and see if it is parallel within YOUR acceptable limits. Even if it is parallel, run the DTI over the full length of the top of the test piece to see that it is neither "kicked" up nor down.

                      2.
                      test that the head and tail stock centres are aligned laterally. Despite advice to the contrary it is not necessary in the first instance to "take a cut". Just get a length of centreless ground round-stock (steel, brass, aluminium or whatever is handy that is accurately round and test it in a vee block with a DTI) and straight (test on 2 vee-blocks on a flat surface ie surface plate, mill table or similar and use a DTI or even use "feelers if needs be). Mount the piece in the 4-jaw chuck and centre it accurately with a DTI and then drill and finally BORE the centre hole to suit the machine centres. Do both ends. Remove the chucks and fit the centres provided to the head and tail stocks. Mount the "centred" test-piece between the centres. Spin it on the centres (by hand will do) and use the TDI to test for "true" (concentricity) along its length. If all is OK within your requirements, run the apron - with DTI on the test-piece and check variations both on the TOP and the front. Any variation of the top will require the tail-stock to be raised (shimmed) or lowered (milled/ground). Any variation at the front is taken out by the tailstock "cross" adjustment. Test it all again to see that all is still OK and readjust if necessary. Do a test cut if you wish,but I'd just about bet that it will be OK. Put a true round piece in the tail-stock chuck a test for alignment - front and top.

                      I hope this helps.

                      I'm expecting some comment ("flak"??) on this - so be it.

                      Comment


                      • #12
                        the kicker to that rollaround is that it's mounted on three wheels so it won't be subject to as much twisting stress as it would be on 4 wheels.

                        my little lathe is loosely mounted on the bench, for some work I don't worry about it but when I'm doing something serious I check and adjust as needed.

                        ken.

                        Comment


                        • #13
                          The ideal state?

                          Originally posted by kendall
                          the kicker to that rollaround is that it's mounted on three wheels so it won't be subject to as much twisting stress as it would be on 4 wheels.

                          my little lathe is loosely mounted on the bench, for some work I don't worry about it but when I'm doing something serious I check and adjust as needed.

                          ken.
                          Ken, thanks for the "kicker".

                          Your lathe is about as unstressed as its ever likely to be.

                          It there is any twist or warp that affects its operation, you are just going to have to find it and learn to live with it.

                          Probably the worst thing to do would be to "untwist" it by (pre?)loading the "feet" in attempt to "correct" it. Might even break the feet (off).

                          Just pack/shim under the wheels and get it as level as you want it and if it must be fastened down do it with the least loading.

                          I'd be more concerned about "vibration" when the lathe spins as "out of balance" problems can be bad news.

                          The reason I didn't include a "test turning" in my previous post was that if the bar (test-piece" length-to-diam ratio was too high (ie too "thin" for its length) you'd have to use the traveling steady anyway and that may well introduce errors or problems of its own.

                          I can say that using a precision engineer's level in my situation is a waste of time for the effort required. I've got one - used it twice and put it away.

                          I use a good correctly "zero-ed" carpenter's level - about 1:1,000 - or better with care.

                          I've used the same system to set up my grinder wheel-balancing edges and I'm damned if my balanced wheel will roll at all. Just stays stationary unless I "nudge" it - then it keeps going until I stop it - both ways - and that's quite good enough for a surface grinder.

                          You will be surprised at how accurate a steel ball on a hard flat smooth surface can be!!.

                          I've set up a flat plate parallel to my lathe "ways" - but spanning them and placed a ring on it and put a couple of balls in it. It will show you the low spot straight away.

                          Better still if you have a "rough" "bulls-eye" (circular) level aligned to the plate as well. Use it first and then the "balls in the ring".

                          And if you want those balls to be really sensitive, just place a small unbalanced rotating load (a small hand-held electric motor) to just touch the plate or the lathe - it will "sensitize" it no end - for an even better result.

                          Just get it "near enough" and unstressed and you'll be surprised at how well it goes.

                          If having the coolant all go down one end or side annoys you - then re-adjust to suit.

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                          • #14
                            "just place a small unbalanced rotating load (a small hand-held electric motor) to just touch the plate or the lathe - it will "sensitize" it no end - for an even better result."

                            Good point Tiff, see "introducing noise" on the DRO jitter thread.
                            Someone there makes the point that it is similar to tapping a barometer to get a true reading.
                            Just got my head together
                            now my body's falling apart

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                            • #15
                              A "shaky" start?

                              Originally posted by Swarf&Sparks
                              "just place a small unbalanced rotating load (a small hand-held electric motor) to just touch the plate or the lathe - it will "sensitize" it no end - for an even better result."

                              Good point Tiff, see "introducing noise" on the DRO jitter thread.
                              Someone there makes the point that it is similar to tapping a barometer to get a true reading.
                              Thanks S&S.

                              I know it works - coz when I was sobering up and leaned on a bench in the Kitchen, every damn plate and cup in the house rattled - and you should have seen my wife and then me - in that order - "move".

                              Re. the "DRO jitter thread" - I've been there - I'd guess since you wrote this item. Go and check it as I might have done (or about to get?) a lot of "damage" there.

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