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  • Adjusting SB bed alignment?

    Thanks all for the advice to check the alignment before figuring weird ways to thread.

    I've tried Rollie's dad's method and realized I didn't know how to insert the shims. It's a '41 9" SB.

    It looks like the bed is attached to the feet? from underneath by probably a hex head machine screw from inside the hollow foot. Feels like that anyway.

    I'm thinking a couple of holes in the bench would allow a socket up there--is that what to do?

    Thanks,

    Gary

  • #2
    No -shim between the front or back foot and the benchtop at the tailstock end.

    Personally, I gave up on shims and instead put four threaded studs up through the bench. So, starting from the benchtop and working up, there is:
    1. A washer
    2. A nut, to hold the stud in place in the benchtop
    3. A nut, for adjustment of the lathe foot
    4. A washer, for the lathe foot to sit on
    5. The lathe foot
    6. A washer, on top of the lathe foot
    7. A nut, on top of the stack

    So, to adjust the foot up, one loosens #7 and cranks #3 upward.
    ----------
    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
    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
    Don't own anything you have to feed or paint. - Hood River Blackie

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    • #3
      Thanks! That sure sounds easier and better.

      Gary

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      • #4
        I've been looking at the feet more carefully and see that the mounting holes are under 1/2".

        3/8" threaded rod seems too thin but I'm not sure about 1/2" either and that would mean enlarging the holes a bit.

        What diameter are your studs?

        Thanks,

        Gary

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        • #5
          Originally posted by gfphoto
          I've been looking at the feet more carefully and see that the mounting holes are under 1/2".

          3/8" threaded rod seems too thin but I'm not sure about 1/2" either and that would mean enlarging the holes a bit.

          What diameter are your studs?

          Thanks,

          Gary
          Although not as easily found, you might try 7/16" hardware if it is available where you are.
          Don Young

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          • #6
            I tie down 3 feet and configure 1 foot for a jacking stud, anchored in the floor, with the ability to control the foot both up and down. You will have to shim the 3 in order to get clearance for the jacking stud.
            Even a crap 3/8 grade 2 bolt, without marking, is rated at 3200lbs of clamping force, I consider this plenty adequate.
            Mike

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            • #7
              I used 3/8". Plenty big enough -- there is not much load on them. All they do is keep the lathe from moving around.
              ----------
              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
              Law of Logical Argument - Anything is possible if you don't know what you are talking about.
              Don't own anything you have to feed or paint. - Hood River Blackie

              Comment


              • #8
                Thanks all again for the help--it's much appreciated.

                I went with 3/8" hardware.

                Is this right?



                Gary

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                • #9
                  Perfect!
                  Mike

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                  • #10
                    Thanks Mike!

                    Gary

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                    • #11
                      Hello,

                      Over the past several days I've been working with Rollie's dad's alignment method.

                      He has the horizontal first so I started with that. Took a bunch of tries but eventually I nailed it. Or at least I think I did.

                      Then went to vertical and I figured the headstock end would be better to adjust so as not to mess up the horizontal, or mess it up as little as possible. I've been raising and lowering quite a bit and only can get about a .001" improvement. From about .0075" to .0065" deviation.

                      Am I doing something obviously wrong?

                      Should I only adjust the tailstock end and maybe start with vertical since that seems to be the coarser adjustment?

                      Originally I used a 1" diameter rod but after reading a bunch of things decided to switch to a 3/4" seamless tube in case the rod was sagging.

                      Also, I understand that with the horizontal adjustment you're torquing the bed by raising or lowering one side, but what are you doing by adjusting both sides of a foot? It doesn't seem like there's much constraining the bed in that direction.

                      Thanks,
                      Gary

                      Comment


                      • #12
                        I didn't follow any earlier questions you may have posted on this, but if you are having trouble after a reasonable number of attempts, you may want to consider some basic considerations.

                        When you shim a lathe, you are trying to twist a cast iron bed that is deliberately designed to be as rigid as possible. So you MUST consider how it is mounted. The mounting points must be at least as rigid as the lathe bed, preferably a lot more so. So if you have this lathe mounted on, say, a 3/4" plywood table top and the mounting points are several inches away from the legs and stiffeners, then you may as well not bother. The plywood will bend a lot more easily than the lathe bed and even if you do manage to set it up, it will CHANGE over time and with humidity changes; totally destroying your work.

                        A dimensional wood bench may be just as bad. Soft woods like pine are really bad. Nails are bad as they can easily work loose. Screws compress wood fibers and this can allow them to loosen or change. If you must use wood, I would recommend a hard wood, like oak. Glue is the best for assembly. Add screws for ease of assembly. Fasteners for the lathe should have large washers to distribute the load over a large area.

                        But a steel table is a lot better. Welded steel would be best. The table should weigh more than the lathe. The legs should have levelers and a means of tieing them down SOLIDLY to the floor. Your lathe bed is completely capable of lifting a table leg off the floor if allowed to. Oh, the floor: the floor must also be solid. Concrete is best, of course. The thicker the better and NO cracks. In a typical garage, you are best off near the outer walls as there should be a footer along the edge and the floor will actually be thicker there. Most contractors will slope the ground below the foundation to reduce the thickness in the middle. A four inch slab may actually be only two inches thick between footers. I poured a 100% four inch slab once and the concrete truck driver could not believe the amount of concrete that went into it. He had seen so many that didn't meet specs that he thought it was the norm.

                        So, solid floor. Solid table solidly ancored to solid floor. Then level the lathe. Otherwise, you are just wasting your time.
                        Paul A.
                        SE Texas

                        And if you look REAL close at an analog signal,
                        You will find that it has discrete steps.

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                        • #13
                          Paul,

                          I guess I'm somewhere in between as far as the bench and floor go. The bench is homemade and pretty sturdy, heavier than the lathe, though not attached to the cement basement floor. The top is a combination of 3/4" ply and a heavy old door--about 2" thick where the lathe is attached.

                          I've been able to get the horizontal alignment to better than .001"--the bed seems to be responding to the adjustments pretty well.

                          However, vertical adjustment doesn't seem to work.

                          I've set up the lathe, as suggested earlier in this thread, so that it's supported by adjustment bolts at the four corners. I can see that by raising or lowering any one corner the bed would be torqued to correct horizontal misalignment--because it's constrained at the other three corners.

                          However, and maybe I'm misunderstanding what I've been reading, to correct vertical misalignment the direction is to shim both corners, either headstock or tailstock side. That's what I'm puzzled about. I can get only a slight difference by fairly large amounts of raising or lowering--it stays within about .006" - .007".

                          It seems to me that the headstock would need to be shimmed.

                          Thanks,

                          Gary

                          Comment


                          • #14
                            On a lathe with 4 mounting points, the vertical alignment is not corrected by twisting the bed with the jackscrew. The vertical alignment is corrected by machining or shimming the headstock, BUT DON’T BE IN A HURRY TO DO THIS. Depending on the length and construction of your test bar, the .007 number that you throw out is probably mostly the measurement of droop, from gravity, of the bar. Even if there is a slight alignment problem, the vertical alignment has almost no effect on diameter and most of this error is corrected when you dial in the horizontal correction with the averaging method. If it faces reasonably flat and doesn’t turn taper, the gods are smiling on you and you are done.
                            BTW, The averaging method needs a truly round test bar to work properly and be sure to verify your adjustments with a two-collar test.
                            Mike
                            Last edited by mf205i; 06-13-2010, 06:03 AM.

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