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How Level is Good Enough?

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  • How Level is Good Enough?

    Hi y'all. This is my first new thread. I am curious how level one reasonably needs to get a taiwanese lathe and a real bridgeport mill respectively when setting them up. I've used these types of machines before but this is my first foray into owning and maintaining them.

    It looks like a machinist level that does .005/foot is much much cheaper than one that is calibrated to .0005/foot. What would be the problems created by the machines being a touch out of level and what is considered reasonable?


  • #2
    At the risk of repeating what has been said before.....

    "Level" to that degree of accuracy is totally unimportant..........


    "All parts alined the same" is pretty important on a lathe.

    So the level with more resolution gives you a closer comparison of whether the headstock end is leveled the same as the tailstock end.

    On teh other hand, the 0.005 level won't go crazy if a few microbes get under one end. it will get you close enough to do a "two collars" test, or the like, which directly measures alinement as it affects performance.

    The 0.0005 level will drive you nuts getting roughed in. But it certainly is accurate..........

    I don't think you need to sweat the Bridgeport..... they tend to be a one-piece lump that doesn't get out of alinement with itself.

    Lathes, planers, etc are the stuff you need a level of some sort to get alinement reasonable on.
    Last edited by J Tiers; 03-17-2007, 01:29 AM.

    Keep eye on ball.
    Hashim Khan


    • #3
      We need to bring out the old Le Blond Portable early in the discussion this time...



      • #4
        How would you align a lathe in a microgravity environment?
        Free software for calculating bolt circles and similar: Click Here


        • #5
          Originally posted by Evan
          How would you align a lathe in a microgravity environment?
          ...with chains and binders.


          • #6
            Aligning lathe in microgravity

            First of thanks Jtiers for the advice. I didn't go back to the 2005 thread and find the discussion until you mentioned that this discussion may have happened before as I hadn't been lurking that long. I've seen enough to know that as level as you can get it is the correct answer and that the reason to level is not due to level in the case of a lathe but ensuring that the bed is not twisted using parallism with the gravity vector as a measurement technique.

            Of course the question is then if the north side of your shop has a vein of uranium ore and the south side doesn't then does the geoid variation between the north and south sides of the shop make the gravity vector point just enough off to drive the pedantic nutso

            Well, Evan, I'd get out my 2 lathe sized surface plates from the locker where the frictionless pulleys and massless ropes are stored. I'd then make the surface plates parallel using stacks of perfectly accurate gage blocks from the same locker. I'd then sandwich the lathe between the plates with one plate pressed firmly against the bottom of the lathe and the other plate above the lathe spaced away far enough not to contact anything held apart by the three stacks of perfectly accurate gage blocks.

            This would of course require adjusting the feet of the lathe to contact the bottom plate. I would then slide a laser phase difference of arrival distance measuring instrument along the top surface plate measuring the distance from the bottom of the top surface plate to the front and back lathe ways. Adjustment of the lathe feet against the bottom surface plate and thus rotation of the alignment of the top surface plate parallel to the bottom surface plate could thus be accomplished. When all the distance measurements are the same then the surface plates are parallel to the ways and there is not twist in the bed.


            • #7
              Pretty clever Cameron... Finally a new twist on lathe untwisting.

              I wonder how much the ways bow upwards if there isn't gravity holding them flat?

              You'd need some serious chip control, and you'd probably want to get out of the way when starting or stopping the lathe.

              On the other hand, why not just skip the lathe and pull the finished part out of your magic locker?


              • #8
                Don't laugh Cameron. I have done experiments with optical alignment on my lathe using a horizontal line laser and prisms to reflect the beam(s) on a wall about 25 feet away. It works quite well. I forget the exact math now for what I calculated as the resolution but I seem to recall I could resolve to about 20 arc seconds.

                I haven't finished those tests as I was planning to use multiple reflections between first surface mirrors to make the path longer. I haven't tried that yet.

                I forgot to mention that I used the prisms as corner reflectors sitting on parallels on the bed ways because that makes the horizontal alignment entirely non critical as it is irrelevant anyway.
                Last edited by Evan; 03-17-2007, 03:13 AM.
                Free software for calculating bolt circles and similar: Click Here


                • #9
                  BTW..... for the amusing gentleman who "trumped the discussion" with the portable LeBlond..........

                  You will notice TWO things about it......

                  1) It sits on 3 supports, so there is no net force twisting anything assuming a sensibly flat and level floor. A sufficiently unlevel floor to give a twist would send it rolling into the corner with bad results.....

                  2) the bed on it is one of the stoutest you will ever see, ion proportion to length and size.... The prospect of getting a serious twist into that seems unlikely.....

                  Keep eye on ball.
                  Hashim Khan


                  • #10
                    Inconsequential thoughts.

                    Carl. I want one of those portable leblonds. Just need a steam tractor to pull it.

                    Evan. In my brief time here, you worry me some days


                    • #11
                      Originally posted by Evan
                      How would you align a lathe in a microgravity environment?
                      Don't you watch Star Trek. First you have to set up an anchored warp field to stabalize the local space around it then set the inertial dampeners to maximum so you can use a wrench, take some superstrings to tie it to your skyhooks (only three never four) and adjust it in the usual manner.
                      The shortest distance between two points is a circle of infinite diameter.

                      Bluewater Model Engineering Society at

                      Southwestern Ontario. Canada


                      • #12
                        Warner and Swasey's turret lathe book shows this old precision level, good to 0.0006" per foot. You can see by the adjustment that level is not what they were after, but rather a tool to verify that all measuring points were in the same flat plane.

                        When you get finished setting up the lathe, you might even want to depart slightly from equal measurements at the ends in order to remove a slight taper. Before doing this, you'd have to make sure that the tailstock has no offset, or use a test bar cut while held only by the chuck. There are numerous threads on this topic that describe bar length, minimum diameter to avoid deflection, etc.

                        Carl, that's a good one. Reminds me of old radio flyer red wagons ... could've used a lathe back then


                        Last edited by nheng; 03-17-2007, 11:34 AM.


                        • #13
                          The confusion results from the fact that people refer to "leveling a lathe", when in fact it is using a level to align a lathe.

                          The level is simply a convenient and relatively inexpensive means of comparing the relative position of various points on the lathe bed to each other. A surface gage and dial test indicator could be used to accomplish the same thing on smaller machines.
                          Jim H.


                          • #14
                            "How would you align a lathe in a microgravity environment?"
                            I wouldn't bother, it's self-aligning
                            Just got my head together
                            now my body's falling apart


                            • #15
                              When it cuts as accurate as you need, then it is aligned well enough.
                              Paul A.
                              SE Texas

                              Make it fit.
                              You can't win and there IS a penalty for trying!