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  • tailstock centering article

    some time back there was an article in either Machinest Workshop or Home Workshop. It concerned using a lenght of all thread and washers. Does anyone know what issue it was in. I have look through all my back issues and can not find it.

  • #2
    I can tell you right now that if it uses a length of all thread there's little hope for any presision. All-thread is not only crooked, and out of round (often lobed) but the threads are often drunken (radial pitch plane nutates). It's great for bolting together logs for swing sets and other rough applications but there's little about it unmodified that's accurate enough to directly diagnose faults in a machine tool. OK I said that not having read the article. I bet there is some cleverness therein that blows my scoff right out of the water. No worry. I'm familiar with the flavor of my feet.

    Take anything in hobby mags with a grain of salt. They have to have content for every issue and there's seldom expertise available for editing incoming copy before it goes into print. I know. I used to write for them.

    Determining the geometry of a suspect tailstock is very simple and requires only a DTI and an accurately chucked slug the same size as the tailstock quill.

    Quite often the neophyte will take some readings on his tailstock, make adjustments to satisfy them, and go on without checking the fit of the tailstock base on the bed. This part usually wears like a rocking chair from being slid over the bed, wearing it so it gradually loses its capacity to restrain the tailstock from small yaw errors. These errors unpredictably affect taper in supported work. Resurrecting the capacity of the typical tailstock to accurate align with the spindle axis requires re-scraping the tailstock base to fit the bed while correcting parallelism of the quill to the spindle axis. Both at once. Then install a fitted shim between the base and the tailstock's upper casting to raise the quill centerline to coincide with the spindle's. Then laterally adjust to bring the qull taper into accurate alignment with the spindle axis.

    Try this; Extend the quill and lock it. Mount an indicator on the carriage to register vertical movement of the quill and set a zero. With the tailstock unclamped press firmly down on one end of the tailstock casting then the other. There should be no change in the indicator reading. Any movement of the indicator shows "rocking chair" error in the base. Rocking chair cannot be corrected by shimming between the upper casting and the base.

    Crank the carriage back and forth so the indicator registers vertical error of the quill height along its extended length. The indicator should read zero ro 0.0005" per foot rising towards the headstock.

    The errors thus revealed in the tailstock may be indicative of the machines overall condition.
    Last edited by Forrest Addy; 03-18-2012, 06:56 PM.

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    • #3
      Originally posted by rolland
      some time back there was an article in either Machinest Workshop or Home Workshop. It concerned using a lenght of all thread and washers. Does anyone know what issue it was in. I have look through all my back issues and can not find it.
      It will work surprisingly well - if you are careful.

      Get a bit of drill rod cut to length - say 8>12". Put it in your 3-jaw chuck and face off and centre-drill each end.

      Put two nuts with two washers between them and jamb-tighten the nuts to secure the washers between the nuts with say 1" of all-thread sticking out- both ends.

      Put one end of the all-thread in your three-jaw chuck and mount the other end on a fixed centre in your tail-stock. Skim-cut the washers at the tail-stock end.

      With the lathe tool at the same setting, reverese the all-thread and skim-cut the second/other pair of washers.

      Repeat for both ends and take a final skim cut with the lathe tool at the same setting.

      Now measure the diameters of the washers at each end. If they are the same, the tail-stock is aligned to the head-stock spindle.

      For a final alignment check and to (re)align the tail-stock, use a good dial indicator (say 0.001" will do), put the indicator on the set of washers at the head-stock end and rotate the spindle by hand to check for run-out and set the indicator to zero.

      Without moving the cross-slide, move the carriage until the indicator is on the washers at the tail-stock end.

      If the tail-stock is aligned the zero-ed indicator will read zero. If not, adjust the tail-stock (using its cross-slide) to zero the indicator. Tighten and re-check the indicator remains on zero. Re-adjust if necessary.

      This may seem a bit "rough and ready" but is works with basic lathe/shop tools and materials.

      There are other "better", (more??) "refined" ways of doing it but they are not much more accurate.

      Its just another "shade-tree mechanic" solution that works better than some who are a bit inclined to be too "finnicky", "old school" and "purist" might allow or believe. I guess they might "analyse" this the the "n^th" degree.

      "Needs must (when the Devil drives) ............................. "

      http://uk.answers.yahoo.com/question...9040735AAfq4Fh



      If the tail-stock is aligned

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      • #4
        Ah! Dumb me. I shoulda guessed. In other words a variation of the two collar alignment method. Better use a hefty hunk of all thread and really sinch the nuts on the washers so they don't come loose when you turn their OD's.

        This as a diagnostic tool of machine alignment detects only the vertical and lateral alignment of the tailstock center at the moment of its application. It's OK for taper - better than OK because reversing the device doubles the error. OTH It has little value in determining the individual sources of error possible in a tailstock.

        These distinctions are important. If all you're concerned with is an immediate taper correction then the All-thread trick is an excellent method for doing so. If your machine is older or has an undetermined wear condition than the two collar trick won't tell you what you need to know about the tailstock.
        Last edited by Forrest Addy; 03-18-2012, 08:14 PM.

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        • #5
          Centeringthe tailstock

          Trying to answer your question I posted in the wrong thread so I will re do it here.


          To quickly center the tailstock you need a test bar and an indicator. A test bar is not that hard to make. The procedure is described in one of our sponsorers lathe videos. Take a 12" bar about 3/4" dia. and drill new centers in both ends. Don't fret about the accuracy. Put a center in the headstock and if you want to fret about something take a truing cut on that center. Install the bar between centers and turn about 1" next to the headstock center.

          Put an indicator in a tool holder and take a reading on the test area that you turned true. It is important to stay at the centerline height. Reverse the test bar between centers so that the good surface is now at the tailstock end. Move the indicator and read the position of the test bar. This shows that mine is about .002 off center.

          Move the tailstock to get a zero reading. The on center indicator holder is easy to make. Here is what mine looks like.
          Mill out the block that has a bottom tab that fits the T- slot in the cross slide. The indicator hole is drilled using a drill in the headstock. This assures that it is on center. The diameter corresponds to the diameter of your indicator. Two holes are drilled and tapped from the top one to hold the indicator in the block. The second positioned to lock the block in the T-slot.


          Boucher
          Byron Boucher
          Burnet, TX

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          • #6
            Originally posted by Forrest Addy
            Ah! Dumb me. I shoulda guessed. In other words a variation of the two collar alignment method..
            well it was a good passionate speech anyway

            .....but I think the quality of the hobby mags might be a little greater than your giving credit for. Proliferation and ease of publishing are issues (pun intended) in all fields - its so easy/cheap to put your words out there there cannot possibly be enough editors in the world to cope with the landslide....hard copy otoh, with associated economics, requires some filtering/editing and our guys both know what their doing and do a fine job at it imo....its the content here and on utube the uninitiated should be wary of.
            .

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            • #7
              Originally posted by Boucher
              .......................................

              Put an indicator in a tool holder and take a reading on the test area that you turned true. It is important to stay at the centerline height.

              ...........................................
              Boucher
              It might be ideal to have the indicator at centre height but it is not necessary. Providing the indicator remains at the same height for all similar diameters and is not more than say about 0.030" above or below centre, any deviation of the indicator will be the same. It really doesn't matter to much either if the indicator is tilted up to say +/- 5 or so degrees. The indicator is being used more as a comparator than a measuring device as after all it is a matter of "zero-ing" ie comparing and not really accurate measuring

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              • #8
                I know how to aline a tail stock I don't need a lecture or this is how you do it I need the article. What is so hard about that

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                • #9
                  Originally posted by rolland
                  some time back there was an article in either Machinest Workshop or Home Workshop. It concerned using a lenght of all thread and washers. Does anyone know what issue it was in. I have look through all my back issues and can not find it.
                  Originally posted by rolland
                  I know how to aline a tail stock I don't need a lecture or this is how you do it I need the article. What is so hard about that
                  Well, as you know what issues it isn't in, it is not too hard to find out what issues it may be in. I assume you know the date/year range as well which will narrow it down further.

                  The better and further you narrow it down and post it here the more likley it is that someone will make the effort to find out and let you know.

                  Have you PM-ed George Bullis as it might be possible that he has a comprehensive index?.

                  Otherwise you may have to go without or do it yourself.
                  Last edited by oldtiffie; 03-18-2012, 10:19 PM.

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                  • #10
                    Frank Ford has a crazy simple method that works great:

                    http://www.frets.com/HomeShopTech/Qu...alignment.html

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                    • #11
                      So far, everybody is seemingly working on the assumption that the MT bore of the tail-stock is concentric with and parallel to the tail-stock quill and that the quill is parallel to the lathe bed and head-stock spindle - they may not be.

                      As soon as a tail-stock is aligned without a test bar it is only correct at that position of the quill in the tail-stock.

                      Any angular misalignment (often due to wear in the vee-ways and "slop/slack" in the tail-stock adjusting cross-slide) will "move" the tip of the drill/centre away from centre and so cause a mis-alignment else-where which may put live or dead centre ends off centre or cause drills to break.

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                      • #12
                        Originally posted by oldtiffie
                        So far, everybody is seemingly working on the assumption that the MT bore of the tail-stock is concentric with and parallel to the tail-stock quill and that the quill is parallel to the lathe bed and head-stock spindle - they may not be.
                        My assumption in that regard is that isn't anything I'm going to do anything about so I'm going to ignore the possibility. However - Frank's method lets you test for all extensions of the tail stock quill rather quickly.

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                        • #13
                          Franks method may be faster and just as accurate with no need to turn a spigot each time if he had two similar centre-drilled disks and use a fixed centre in both the head-stock and tail stock or alternatively get a bit of scrap in a 3-jaw chuck and turn a 60 deg "centre" on it and use the tail-stock centre as before..

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                          • #14
                            Originally posted by rolland
                            some time back there was an article in either Machinest Workshop or Home Workshop. It concerned using a lenght of all thread and washers. Does anyone know what issue it was in. I have look through all my back issues and can not find it.

                            The article you are looking for is Steve Acker’s review of a Grizzly lathe and it ran in the June/July 2008 issue of Machinist’s Workshop. You can order this issue by calling Village Press at 800-447-7367.

                            George
                            George

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                            • #15
                              George
                              Thank you thats what I was looking for

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