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  • Tailstock Test Bar

    A buddy Bud (not a pun) sent me this ebay link (ground test bar with centers) this morning..

    http://www.ebay.com/itm/ws/eBayISAPI...:B:WNA:US:1123

    ...and it made me wonder why the HSM couldn't make his own from drill rod.

    (1) Using a 4 jaw, chuck up the rod and zero it with just an inch or less protruding.
    (2) Face off the end and Single point a counter sink.
    (3) Repeat 1 & 2 on the opposite end.

    Am I missing something?
    Last edited by Chris S.; 10-19-2011, 04:47 PM. Reason: Replace wrong link!

  • #2
    Assuming your talking about a test bar and not a tailstock barrel you posted a link to:

    I had one made at a shop close by out of 1.5" drill rod

    I could not center drill accurately with my tailstock being out of alignment and also needing to be shimmed.

    I paid $30 bucks for the test bar. Had my tailstock shimmed, dialed in .001 over 12" height wise and side to side in about 20 mins.
    https://www.flickr.com/photos/csprecision

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    • #3
      Test Bar

      To answer the question - yes you can make your own as you described. There is no reason why not. Would it be accurate to millionths? Probably not, but plenty good enough for nearly any normal work.

      Comment


      • #4
        Here's a little trick I read about and tried and it actually works.

        Go find an old large printer to tear apart. The old tractor feed models or similar. The print head rides on a nice thick stainless round bar that is rather straight. Use that as your alignment bar. Now I don't remember where I read about that but I did at the time have at least 3 old style printers to play with. I found one at least an inch in diameter and at least 20" long. Turns out the bar truly is rather straight and I keep it tucked away for the day lathe alignment comes into question
        "To invent you need a good imagination and a pile of junk" Thomas Edison

        Better to have tools you don't need than to need tools you don't have

        73's KB3BFR

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        • #5
          Originally posted by Chris S.
          A buddy Bud (not a pun) sent me this ebay link this morning..

          http://cgi.ebay.com/SOUTH-BEND-10K-L...item564521fa5d

          ...and it made me wonder why the HSM couldn't make his own from drill rod.

          (1) Using a 4 jaw, chuck up the rod and zero it with just an inch or less protruding.
          (2) Face off the end and Single point a counter sink.
          (3) Repeat 1 & 2 on the opposite end.

          Am I missing something?
          Did you mean one of these? Lathe Test Bar
          The problem is drill rod is not perfectly round.

          Comment


          • #6
            Sorry guys, I posted the wrong link! I edited that post but here's the link anyway. It's no wonder I was getting such odd replies!

            http://www.ebay.com/itm/ws/eBayISAPI...:B:WNA:US:1123

            As you can see, it's a ground test bar with centers. Scroll down the page when you get there..

            Chris
            Last edited by Chris S.; 10-20-2011, 11:48 PM. Reason: sp

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            • #7
              Originally posted by Highpower
              Did you mean one of these? Lathe Test Bar
              The problem is drill rod is not perfectly round.
              No, I'm aware of this technique and this test bar. It's used for checking bed twist - leveling and way wear. It's not used for TS alignment,.... unless it has centers.

              No, I didn't know that drill rod is not perfectly round. I was under the impression that drill rod was ground to dimension. When you say "not perfectly round", to what degree are you talking about?

              Chris

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              • #8
                Originally posted by Highpower
                Did you mean one of these? Lathe Test Bar
                I should have mentioned that this is a very good price if the shipping doesn't kill ya... and yes, this does have centers.

                Chris

                Comment


                • #9
                  Chris, most drill rod I have seen shows a max T.I.R of .005" for the "standard" tolerance. Drill or reamer blanks usually fair better than that I believe, but then you are limited on length.

                  And the shipping (Royal Mail) on that test bar is quite cheap actually. I think I paid less than $15 when I ordered mine.

                  Comment


                  • #10
                    You really don't need anything precision ground to determine error in the tailstoock quill. There a couple of simple tests:

                    1, Droop. Fully extended the quill. Register and indicator on the end and set a zero iin the vertical plane. Scan the extended length of the quill and note the sweep. Any amount of "droop" is characteristic of taistock wear. The front edge of the tailstock base wears more rapidly than the rear. Return to the extended end and note if the zero repeats.

                    1a. Do the same side to side and note any error conditions. Push the end of the taistock quill both ways. Reading discrepancies more than 0.0005" indicates wear. Bi-stable (the tailstock does not recover from the push) indicates moderate to severe wear on the V way. It's not automaically centering. Mixed in with the reading of excessive clearance of the quill in the quill bore. Conduct tests to separate with wear conditions.

                    2. Determning parallelism error. Machine a stub the same diameter as the tailstock quill and leave it in the chuck. Set up and zero an indicator on it to register in the vertical plane. Extend the tailstock quill. Crank the carriage so the indicator contacts the extended tailstock quill and note the reading. On any but a new lathe this should register some out of parallelism. The amount of error should be recorded on a sketch. Go back to the headstock and register the indicator on the stub without disturbing the setting for a repeat zero. If the zero repeats your out of parallelism reading can be recorded for posterity or used to determine the amount of shim used to raise the tailstock up to alignment with the headstock.

                    This is simple machine tool survey technique and needs no special fitted tapers or precision ground bars. Don't get me wrong. Certified proof bars are a great convenience but it's a use-once item. They take many hours of time to make of cost several hundred dollars to buy. Once used they sit on a shelf, a white elephamt. They are needed about once a generation in any but a professional rebuild shop.

                    If you need to conduct a partial survey for spindle tailstock alignment, the two collar tests and plug tests are as accurate and only a little more time consuming than using a certified proof bar.

                    I've surveyed and run test sheet checks on used and rebuilt machine tools. A few cases my results were challenged and my use of two collar tests etc disparaged. After some time and expense a cetrified test bar was acquired and the test re-run by another. Funny thing: we both got the same results recognizing small descrepancies inherent when working to the limits of the test apparatus.

                    Worn out is worn out.

                    Note, I deliberately glossed over and inserted petty errors in part of the above post. This is something I seldom do but I did this time thinking a few of you may enjoy finding the dubious and erroneous and pounding on them.
                    Last edited by Forrest Addy; 03-18-2012, 08:08 PM.

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                    • #11
                      My question will be this . Just how many of you Have a perfect Lathe any way . I have only ran a very few brand spanking new machines in my life time . Most of the lathes I have ran were worn out to ever ones slandered here. And I was still able to make good parts. So what gives.
                      Every Mans Work Is A Portrait of Him Self
                      http://sites.google.com/site/machinistsite/TWO-BUDDIES
                      http://s178.photobucket.com/user/lan...?sort=3&page=1

                      Comment


                      • #12
                        Originally posted by lane
                        My question will be this . Just how many of you Have a perfect Lathe any way . I have only ran a very few brand spanking new machines in my life time . Most of the lathes I have ran were worn out to ever ones slandered here. And I was still able to make good parts. So what gives.
                        Well, that wasn't my question; was it? This is an alignment/setup aid, just like a machinists level and just as relevant.

                        Chris

                        Comment


                        • #13
                          Tail stock test bar.

                          A test bar is not that hard to make. The procedure is described in one of our sponsorers lathe videos. It is well past happy hour here but I will try. 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 the 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. Move the tailstock to get a zero reading. The video also details how to make a good holder for this.
                          Hope this makes sence when I read it tomorrow when I am sober.
                          Byron Boucher
                          Burnet, TX

                          Comment


                          • #14
                            Originally posted by Boucher
                            A test bar is not that hard to make. The procedure is described in one of our sponsorers lathe videos. It is well past happy hour here but I will try. 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 the 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. Move the tailstock to get a zero reading. The video also details how to make a good holder for this.
                            Hope this makes sence when I read it tomorrow when I am sober.
                            Well, I must confess that I've read threads using the 2 collar method more times than I care to remember but this technique is a first for me. I reserve the right to not judge it until you're sober.

                            Chris

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                            • #15
                              Originally posted by Chris S.
                              No, I didn't know that drill rod is not perfectly round. I was under the impression that drill rod was ground to dimension. When you say "not perfectly round", to what degree are you talking about?
                              I've got a chunk of 1.25" O-1 that mics pretty close, but stick it in a V-block with an indicator and it'll set the needle moving pretty good when turned - it's lobed from centerless grinding into a trichordal form. Naturally I trusted the micrometer when I tried to put it into a 1.2500 hole, figured it out when rotating a piece between centers and the indicator showed it "lumpy".

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