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  • Alignment Problem on SB Lathe

    I'm in the final stages of my rebuild of a South Bend 13" lathe. I've encountered an alignment problem which I have no idea how it happened and I don't know how to correct it. As you can see in the picture, there is about 0.050" vertical misalignment between the head stock on left and the tail stock on the right. There is no misalignment between the two in the front to back direction.



    Both the head and tail stock are sitting flat on the lathe bed rails. I don't understand how such a misalignment could occur. On the bottom of the tail stock there is no way to adjust the tail stock higher.



    Can anyone offer suggestions on why this happened and how to correct this misalignment problem? Thanks.
    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.

  • #2
    From the picture it's hard to tell if the tail center is sitting low or in front of the center in the chuck. Since you mentioned no height adj. on the tail it's possible that the tail is from another machine. But judging from the overall looks of the quill there is a lot of abuse / neglect there.
    Only other thought would be that your chuck is gripping way off center.

    JL................

    Comment


    • #3
      Put a center in the SPINDLE TAPER, not in the chuck. Put another in the tailstock. Retract the ram of the tailstock as far as possible without ejecting the center. Check the alignment again.

      Clamp the ram with it's clamp, and see if that makes any difference

      If still low, then the standard "make-do" remedy is to put a shim between the top and bottom parts of the tailstock to bring it up to the right height.

      While you are looking at possible problems, try extending the tailstock ram about an inch, and seeing if the ram can move up and down relative to the casting. If so, which is likely, and common for older machines, it is possible that the ram "droops" when extended.

      You can extend the ram and check the alignment at several extensions. Also see if using the clamp will change the misalignment.

      The tailstock can wear at the front edge of its contact with the ways, which causes the ram to point down somewhat. Shimming up at the front can fix that for all positions. This looks like your main issue, from the pics.

      The tailstock can wear more evenly and just settle down evenly (usually not as much as you show). Then you can shim up all around. This can also be if the tailstock is from a different machine, same remedy.

      The ram and it's hole through the tailstock casting can wear so that the ram droops down. For that the casting is bored out straight, and a new ram made to fit. (Or you shim up and use the ram position that is best when clamped).

      Usually ther is some combination
      1601

      Keep eye on ball.
      Hashim Khan

      Comment


      • #4
        My SB 9 the tail stock was higher. Someone had used hacksaw blades to shim it. I went to the auto parts store and got several cheep feeler gauges and used those to shim it.

        Sent from my SM-G920P using Tapatalk

        Comment


        • #5
          Just chuck up Morse reamer and ream your tail stock, is fast to do


          Dave


          Originally posted by BigBoy1 View Post
          I'm in the final stages of my rebuild of a South Bend 13" lathe. I've encountered an alignment problem which I have no idea how it happened and I don't know how to correct it. As you can see in the picture, there is about 0.050" vertical misalignment between the head stock on left and the tail stock on the right. There is no misalignment between the two in the front to back direction.



          Both the head and tail stock are sitting flat on the lathe bed rails. I don't understand how such a misalignment could occur. On the bottom of the tail stock there is no way to adjust the tail stock higher.



          Can anyone offer suggestions on why this happened and how to correct this misalignment problem? Thanks.

          Comment


          • #6
            Originally posted by smithdoor View Post
            Just chuck up Morse reamer and ream your tail stock, is fast to do


            Dave
            Show us how to do that on YOUR lathe.

            Tom
            Tom - Spotsylvania, VA

            Comment


            • #7
              Originally posted by smithdoor View Post
              Just chuck up Morse reamer and ream your tail stock, is fast to do


              Dave
              That seems like a remarkably bad thing to do.

              There is no problem with the taper (that has been mentioned, at least)

              The reamer can cut space for the center's taper at the top side, but unfortunately does not fill in any at the bottom, so the result will be an egg shaped and useless taper that won't accept a center any more.

              Even if it COULD be done, that would make the center position change as the ram goes in and out, if the cause of the issue is wear on the T/S bottom, as it appears to be.

              The only case in which the idea could work is if the tailstock was low but still parallel. And you still have the problem of the egged-out hole.

              No, the straight-ahead solution is to shim up to change the height. Where the shim goes depends on whether the T/S is pointed down, or is level but too short heiightwise.

              Even if the T/S was re-scraped, there would have to be height added, in the form of Turcite, or other material functioning as a shim.
              1601

              Keep eye on ball.
              Hashim Khan

              Comment


              • #8
                taper ream 50 thou offset? lol..


                Yes, as Jerry said - first the put the center in your head-stock not the chuck. Or.. if you want just just turn the chucked point from any material with your compound then measure. Turning the stock removes any errors induced by the chuck.

                If it's still out, and your bed is good, shim the tail stock.
                Last edited by lakeside53; 12-09-2016, 04:41 PM.

                Comment


                • #9
                  Yeah, just shoving an MT reamer up the TS without checking for all that other stuff first is a wonderfully wrong approach....

                  Just to add to JTier's lovely list of things to check when you're looking for sag in the ram while at full or near full extension you can mount a dial or test gauge on a magnetic mount on your cross slide and with the TS sitting in one spot run the finger of the gauge along the ram watching for height changes. With this same setup you can test for most or all of the other possible issues with the ram fitting the TS. If the ram turns out it fits the body nicely and there's little or no play and tightening it does not cause it to move then it's wear with the body of the TS. Or you've got some serious wear in the bed of the lathe where the tail stock runs. That would be pretty obvious pretty fast though I would think. But for giggles you could try that ram sag measurement near the chuck and then again near the tail of the bed and see if it changes. Of course this MIGHT include any wear in the part that supports the carriage. But if it measures out different it does suggest some serious bed wear.

                  The common trick for when you need a quick center and you don't want to remove the chuck is to chuck up a bit of round bar scrap and turn a fresh center. Then you KNOW it's dead on to the spindle axis because it was turned in place. Using the center the way you are means it is subject to any off center holding of the chuck. You can tell that by turning the chuck by hand and see if the point orbits around.

                  Where you go with all this will depend on the results from the tests and condition of the actual lathe bed. Shimming between the lower and upper portions of the TS is certainly one option and if done well isn't a bad way to proceed. But if it needs this much correction i think I'd want to look into the new miracle epoxy rebuilding options like that Turcite or some other option.

                  I also hate to say this but the pictures show a ram that is very scored up and the running areas of the bottom of the TS look badly scored as well. I suspect that this lathe saw lots of abrasive grit or metal that was never cleaned up well or some other issue. So it's quite possible that you'll be looking at some fairly major work to make things right.

                  Comment


                  • #10
                    That's a makeshift repair, at best. Moving the center line of a bore by 0.050" with a reamer is going to be a difficult job. Chances are it will move it only part of that distance and introduce an angular error at the same time. A total cluster fu<#. I wouldn't do it that way.

                    1. DO use a center in the HS bore, not in a chuck.

                    2. You should check to be sure that both the head stock and the tail stock are firmly seated on the lathe bed. No chips or other things between them.

                    3. You should check that both the head stock and the tail stock bores are parallel to the bed. If they are not, then the misalignment may be due to an angular error.

                    4. If, after the above changes and checks, you still have this misalignment then you need to do one of two things. Raise the tail stock or lower the head stock. Since scraping 0.050" from the head stock would be a lot of work, I would raise the tail stock.

                    Raising the tail stock can be done with shims. My SB9 tail stock is a two piece assembly and shims could be inserted between them. But the 13" may be different. If you can not do that, you can glue them to the bottom surfaces that contact the bed but you will need two different sizes of shims for the flat and Vee parts of the ways. The shims for the flat way would be the amount you want to raise it. But the shims for the Vee way would be only 0.707 times that value.



                    Originally posted by smithdoor View Post
                    Just chuck up Morse reamer and ream your tail stock, is fast to do


                    Dave
                    Paul A.

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

                    Comment


                    • #11
                      Just about a year ago we had this issue on an old swedish lathe, the tailstock had worn down 1 mm, the V-slot in the bottom was already worn to a new angle as the flat guide portion had worn down. And the ram was very loose fit to the bore and the bore had bellmouthed.

                      The fix was to first remachine the lower portion by milling the flat & V-guide to proper height relation (measured from the bed of the lathe), this assured that the top side of this lower portion now sits parallel to the ways and the step on it is exactly perpendicular to the ways.

                      Next we reassembled the parts on the lathe, measured how much shimming we need to get the center pretty much at the right height and water jetted a couple of shim plates from stainless steel of suitable thickness. Then the tailstock was assembled and we bored the bore for the quill, it went 0.6 mm up in diameter to get it clean from end to end. The height for the bore was measured from the lathe itself by turning a scrap piece and measuring the diameter, divide to get the radius and measure from the flat way to the top of the part. The location sideways was just centered in the existing bore, the tailstock afterall has an adjustment for sideways movement.

                      While all this was cooking, we sent out the quill to be hardchromed so that it grew 0.8 mm in diameter. We also instructed to mask the whole inside of it and the keyway slot, as they were all in good shape. When we got it back, the diameter was 1 mm bigger than before, so it took a bit more grinding to get it to the proper size. I put a dead center in the quills taper and in the other end where the nut was sitting in a very tight fit bored hole, I made a tightly fitting plug with a center hole in it. I had to make a female center for the cylindrical grinder so I could put this quill contraption between centers, get my headings and grind it straight and to dimension.

                      Just a couple words of warning: hardchrome in dust form is not a substitute for oxygen, so wear a mask. Other warning is that it acts like a diamond dresser for the grinding wheel, I never had to sharpen the wheel but boy did I have to grind way more by the dials han I actually took off from the hardchromed surface!

                      After all this the remaining parts were oiled, assembled and a witness mark/line was scratched on the quill to indicate the position at which it ejects a standard tanged taper. (don't ask me why I want to know where that point is...)

                      Yeah, way more easy to do when you have big machines and long enough tools than at home shop level.
                      Amount of experience is in direct proportion to the value of broken equipment.

                      Comment


                      • #12
                        This seems obvious, but - is that an MT taper dead center in the chuck? Or is it a straight shank? Maybe just the picture, but the dead center in the chuck looks out of square with everything else, which a tapered shank would do.

                        Also, noticing the apparently hand ground sections on those centers and not knowing their history - have you tried rotating the tailstock center 180* and checking again? Do you know for sure those dead centers are straight?

                        Originally posted by BigBoy1 View Post

                        Last edited by Yondering; 12-09-2016, 05:49 PM.

                        Comment


                        • #13
                          Originally posted by smithdoor View Post
                          Just chuck up Morse reamer and ream your tail stock, is fast to do

                          That's the worst thing you could ever do for a multitude of reasons.
                          If one was able to actually pull it off, the taper would seat so deep into the quill that the point would be behind the edge and the reamer would bottom out long before the hole was reamed true. What would your next suggestion be, trim the edge of the quill back.

                          JL....................

                          Comment


                          • #14
                            It works great simple to do.
                            I use this one on more than one lathe quick and accurate
                            Just Need a good reamer
                            If try shimming can work there way out use lock tie on one side

                            Dave

                            Originally posted by JoeLee View Post
                            That's the worst thing you could ever do for a multitude of reasons.
                            If one was able to actually pull it off, the taper would seat so deep into the quill that the point would be behind the edge and the reamer would bottom out long before the hole was reamed true. What would your next suggestion be, trim the edge of the quill back.

                            JL....................

                            Comment


                            • #15
                              Originally posted by smithdoor View Post
                              It works great simple to do.
                              No, it will not work as others have pointed out. Your method is a hack of the worst kind, it will not correct so greatly misaligned hole, it will be egg-shaped or too deep once clean and it will have a serious angular error, i.e. not parallel to the ways or not on the axis of the quill.

                              Please point out the machines you have done this to, so everyone else can avoid your shoddy workmanship and bad practices.
                              Amount of experience is in direct proportion to the value of broken equipment.

                              Comment

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