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  • #16
    Very interesting discussion. The only tests that matter are the test bar alignment checks performed with the spindle retracted and extended. At the end of a 12" test bar; horizontal is +- .0005", and vertical is high +.0005". 4 tests to perform. This will also confirm the alignment of the spindle body.
    To see how I do it start at post #223 in this topic;
    http://www.practicalmachinist.com/vb...update-146913/
    and post #125 in this topic;
    http://www.practicalmachinist.com/vb...ew-toy-163406/
    Read them very carefully, I've gotten burned more than once on Monarch tailstocks after scraping them by the book, and had to make some corrections, after doing the test bar checks.
    Harry
    Last edited by beckley23; 09-03-2010, 11:09 PM.

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    • #17
      Originally posted by rkepler
      At this point the top casting was scraped and used as a master for the base casting, so the base top is already scraped and flat.
      Russ, that's actually different than what Connelly describes.

      First, the tailstock base is scraped straight/parallel, and spotted on an unworn part of the lathe bed. Then the top of the tailstock base is scraped on a surface plate, propped-up with parallels (to clear the transverse slide) and a dial indicator on the bottom ways to indicate parallelism of the tailstock base top (Figure 26.46 on page 294). Then the top is assembled on the aligned tailstock base.

      If the spindle is off axis with the headstock, Connelly indicates that you correct by scraping the v- and flat ways of the tailstock base. In other words, the tailstock top is never scraped, as far as I can tell.
      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

      Comment


      • #18
        Lazlo,
        IIRC, Connelly does say to scrape the bottom of the top. If I had done that, I wouldn't have scraped the bottom deliberately out of parallel to the bed to make the test bar correction. Monarchs' tops have the male transverse way. Either way, it's a tough job.
        Harry

        Comment


        • #19
          Originally posted by beckley23
          Lazlo,
          IIRC, Connelly does say to scrape the bottom of the top.
          Maybe I'm missing something, but I'm reading "Final Alignment of the Tailstock" on page 295, and it says:
          "In preparation for this final alignment, the tailstock top and the tailstock base are assembled and placed on the bed of the lathe.
          ...
          The first test consists of checking whether the axis of the fully extended tailstock spindle is parallel to the outside inverted V-ways of the bed in the horizontal plane.
          ...
          The second test consists of checking whether the axis of the fully extended tailstock spindle is parallel to the out inverted V-ways of the bed in the vertical plane.
          ...
          If the unilateral tolerance is exceeded in either test, then the V-slide (1) and the flat slide (2) of the tailstock [base] shown in Fig 26.44 must be scraped.
          ...
          Before beginning this operation, a little reflection should enable the operator to determine how to scrape the tailstock V-slide so as to "throw" the axis of the spindle in the proper direction."
          Last edited by lazlo; 09-03-2010, 11:25 PM.
          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

          Comment


          • #20
            Harry, You are a class act. I mean that in a good way. The first time through Your rebuild posts I was waiting with great anticipation for the next series of posts .
            They are just as entertaining and educating this time around.
            Thanks for all Your effort in recording and sharing the rebuilds.

            I'll do some more measuring and note taking this week end and report back what I find.


            Steve

            Comment


            • #21
              instead of scraping the top of the tail stock base to do that?
              Because it is easier to scrape/correct. You can do that on the granite plate.


              You can read as many books as you want, they keep telling you one way or an other. But they all forget telling you a few very simple rules:
              * Try to distribute geometric corrections evenly over all surfaces. Do not try (unless necessary) to handle 3 or more corrections on one surface.
              * Always do the correction at that surface (of the two) that is easier to handle. Be it by weight, ease of access, ease of bluening, etc.
              * The rule to work from bottom to top is not the bible. It can be speedier to make one surface just match and come back later to correct it for geometry.

              Try to envision the process and see what happens. Try other sequences and see what you gain. Don't believe any books that dictate a sequence.


              Nick

              Comment


              • #22
                If the unilateral tolerance is exceeded in either test, then the V-slide (1) and the flat slide (2) of the tailstock [base] shown in Fig 26.44 must be scraped.
                That's quite stupid. Only correct alignment in the horizontal plane at the TS's base. For the vertical plane, the surface between base and top is much easier to correct.
                Alone the fact that the base's bottom surface is a combination of an Vee and a flat is a challenge (to some extend) by it's own. See this video for a better understanding.

                But, I would argue that it is the same thing to some degree..... since both the ways and the X-slide are referenced to the spindle axis..... One is at right angles, the other should be parallel.
                It's not the same thing to any degree. The bed is only a linear reference, not a planar one. Only together with the direction of the X-guide you have a planar reference. But the X-guide is not a part of the bed.



                Nick
                Last edited by ; 09-04-2010, 04:44 AM.

                Comment


                • #23
                  How the book says.................

                  Unless there is a geometric reason, the order of scraping is arbitrary. Connoley even says so, and it is of course true.

                  The point is to find the original reference that is hardest to change, and then use that as a reference.

                  For instance, on a horizontal mill, one would likely take the spindle as a reference, and surfaces of rotation around it will then define the planes parallel to which the knee and table must travel. From that the infeed travel is set at right angles to those plane, which means parallel to the spindle.

                  With the tailstock, the bore is the most trouble to scrape, so if it is good, you would reference things to it..... the bottom of the T/S top is much easier because it has a recess and not a projection on the bottom, so that would be first. Then the bottom part of the T/S scraped To the top. And, yes, for "support", i.e. non-moving bearing. No need for 30 points /inch ^2.


                  Originally posted by MuellerNick

                  It's not the same thing to any degree. The bed is only a linear reference, not a planar one. Only together with the direction of the X-guide you have a planar reference. But the X-guide is not a part of the bed.

                  Nick
                  Not what I said...............

                  The point is that while you would not use the bed as a reference for scraping the X-slide, when you are DONE, you WILL have the bed and X-slide travels at right angles........(within the usual slight offsets to accommodate wear and spring, which you have mentioned.....) But of course what we mean is at right angles in "projection"........ projection onto a plane parallel to that defined by the two travels.

                  if that were not so, then the X-slide would face a cone. or the carriage travel would turn a cone.

                  It is a question not of result, but of reference. BOTH reference the spindle.

                  And, of course, as you point out, so long as the X-slide is correctly referenced to the spindle, it really is not an issue if the plane defined by the two travels is exactly "level". The lathe would work as well if it were bolted with its feet to a wall....so long as it is rigid. (A "real" non-rigid lathe might sag in new directions if the feet were bolted to the wall.)
                  4357 2773 5647 3671 3645 0087 1276

                  CNC machines only go through the motions

                  "There's no pleasing these serpents"......Lewis Carroll

                  Comment


                  • #24
                    Originally posted by lazlo
                    If the spindle is off axis with the headstock, Connelly indicates that you correct by scraping the v- and flat ways of the tailstock base. In other words, the tailstock top is never scraped, as far as I can tell.
                    Look at 26.52 (page 293), where he says:

                    <<
                    The Tailstock Base

                    This unit consists of 3 surfaces which are scraped. They are enumerated as follows:

                    1. The V-slide
                    2. The flat slide
                    3. The top surface.
                    >>

                    On the following page is Section 26.54 where he describes scraping the top surface of the tailstock base.

                    So the process Connelly has you do is to make sure that the top casting is correct (quill travel, flat bottom, etc.) and the tailstock base top is flat and level. If both are correct they should mate well, and at that point all you should have to deal with is some transverse error as well as height correction.

                    I can't remember the sequence I followed on my 10ee tailstock, but I definitely scraped the top of the base for flatness then the V and flatways for level. Most of that was not for the fit of the tailstock, but instead to use the base as a sliding member to check the spindle alignment to the bed when refitting the headstock to the base.. I don't recall doing much for the top casting, maybe just a quick check against the base. But then I wasn't moving a tailstock from a different machine and was just correcting for wear and expected the tailstock to (mostly) fit my lathe already.

                    Comment


                    • #25
                      Originally posted by MuellerNick
                      Originally posted by Connelly
                      If the unilateral tolerance is exceeded in either test, then the V-slide (1) and the flat slide (2) of the tailstock [base] shown in Fig 26.44 must be scraped.
                      That's quite stupid. Only correct alignment in the horizontal plane at the TS's base. For the vertical plane, the surface between base and top is much easier to correct.
                      Alone the fact that the base's bottom surface is a combination of an Vee and a flat is a challenge (to some extend) by it's own.
                      I agree Nick. I was just pointing out that most people don't follow Connelly's description to the letter, because he has some oddball comments.

                      Connelly also doesn't believe in shimming to re-align the spindle after scraping the bed -- he indicates that you should scrape the headstock down to match.
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                      Comment


                      • #26
                        Originally posted by rkepler
                        Originally posted by Lazlo
                        If the spindle is off axis with the headstock, Connelly indicates that you correct by scraping the v- and flat ways of the tailstock base.
                        In other words, the tailstock top is never scraped, as far as I can tell.
                        Look at 26.52 (page 293), where he says:

                        The Tailstock Base

                        This unit consists of 3 surfaces which are scraped. They are enumerated as follows:

                        1. The V-slide
                        2. The flat slide
                        3. The top surface.

                        On the following page is Section 26.54 where he describes scraping the top surface of the tailstock base.

                        Right, that's what I quoted above: Connelly scrapes in the bottom of the tailstock base, then the top of the tailstock base, but he never scrapes the tailstock top. He does all the correction with the tailstock base.

                        I don't really understand why.

                        Nick is suggesting the same process as Connelly for the tailstock base: get the bottom spotted, and then get the top horizontal with a scraping flat and measuring the planarity by elevating the base above the transverse slide with parallels. But Nick and Harry (and I think you?) are correcting the spindle axis by scraping the tailstock top, which seems to be a lot easier than scraping the V-slide, as Connelly suggests.

                        Harry and/or Nick: you should write a book. There are a lot of folks who would buy a modern version of Connelly's book. MTR is painful to read.
                        Last edited by lazlo; 09-04-2010, 11:08 AM.
                        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                        Comment


                        • #27
                          Originally posted by lazlo
                          Right, that's what I quoted above: He scrapes in the bottom of the tailstock base, then the top of the tailstock base, but he never scrapes the tailstock top. He does all the correction with the tailstock base.

                          I don't really understand why.
                          Partially correct - in Section 26.51 he scrapes the base of the top castings and makes sure that the quill (he says ram) is parallel to the bottom and the bottom spots well. (The previous section discusses the transverse and loose quill corrections and dismisses them as "machining operations"). So when the tailstock top casting is complete it is correct in all alignments.

                          But you're right that all corrections are later done on the tailstock base casting, probably because if the previous procedure was followed all you should have at that point is some slight corrections, and if they are slight it might well be easier to scrape the base/bed interface than the base/top - it was in my case as there was a lot less contact in the former. But I would expect that this is different for different styles of tailstocks.

                          Comment


                          • #28
                            Originally posted by rkepler
                            Partially correct - in Section 26.51 he scrapes the base of the top castings and makes sure that the quill (he says ram) is parallel to the bottom and the bottom spots well.
                            You're absolutely right Russ -- I missed that. Sorry!
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                            Comment


                            • #29
                              I don't really understand why.
                              You have to look at Connelly in a different angle.
                              It's an old book, people had different writing styles and the users different requirements. The way it is written, it is very dictative (SP?). He didn't want to make the readers think about it, he wanted to get them to work.

                              No, I won't write a book or make a complete video, because that is an impossible task (or lots of work). I can give you hints, comments, and drive you in the right direction. But you have to make your own decisions (and learn by your faults).


                              Nick

                              Comment


                              • #30
                                Originally posted by lazlo
                                Right, that's what I quoted above: Connelly scrapes in the bottom of the tailstock base, then the top of the tailstock base, but he never scrapes the tailstock top. He does all the correction with the tailstock base.

                                I don't really understand why.

                                Nick is suggesting the same process as Connelly for the tailstock base: get the bottom spotted, and then get the top horizontal with a scraping flat and measuring the planarity by elevating the base above the transverse slide with parallels. But Nick and Harry (and I think you?) are correcting the spindle axis by scraping the tailstock top, which seems to be a lot easier than scraping the V-slide, as Connelly suggests.

                                Harry and/or Nick: you should write a book. There are a lot of folks who would buy a modern version of Connelly's book. MTR is painful to read.
                                Based on the book and the fact that My t.s. top is flat and in plane with the t.s. spindle I thought it should be left alone and that the corrections should be made to the base top and bottom, especially since the base bottom is in dire need of re scraping any way and the fact that it is easier to handle.

                                I don't want more work than what is needed and I have no reason not to believe Harry and Nick, after all they have scraped more tail stocks than I have. Counting this one, so far I haven't scraped any.

                                Steve

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