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Aligning center punched work in the 4-jaw?

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  • Aligning center punched work in the 4-jaw?

    I have center punched an off center mark on a rectangular block. I want to put it in the 4 jaw to drill then bore a hole there. So far my thinking is to put a center in the tailstock and just keep adjusting the chuck jaws until it seems to line up. Suggestions welcome!

  • #2
    Search: "lathe wiggler plans"

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    • #3
      I had the same problem recently. I drilled on the pop mark with a centre drill, put a solid centre in the tailstock, then used this to locate the block against the face of the 4 jaw, with the jaws well open. I locked up the tailstock barrel, then moved the jaws up to touch the block gently at first, then more firmly, a bit at a time on each jaw in turn. Final check was to hold a DTI against the centre, having unlocked the barrel clamp,and rotate the work, making any adjustments needed.
      Sound a lot, but honestly, it didn't take long.
      'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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      • #4
        The old time way to do that is to make up a long flexible rod with a concentric point on it. Maybe 1/8" diam. X 12" long. Put the square end in the tailstock chuck and the pointed end in the punch mark on the work. Put a dial indicator on the side of the rod close to the workpiece. Turn the chuck and see how far the indicator needle moves. Adjust the chuck jaws to get a constant reading all the way around.

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        • #5
          The way I do it is a combo of some of the things mentioned above.

          Place a center in the tailstock.

          Close the center up against the pop/center in the work to hold it against the chuck.

          Close the chuck jaws on the work.

          Back the tailstock out.

          Place a second center inbetween the tailstock center and the work pop/center.

          Indicate the second center.

          Adjust the chuck until the "floating" second center runs true.


          -Bob

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          • #6
            Originally posted by Richard P Wilson View Post
            I drilled on the pop mark with a centre drill, put a solid centre in the tailstock, then used this to locate the block against the face of the 4 jaw, with the jaws well open. I locked up the tailstock barrel, then moved the jaws up to touch the block gently at first, then more firmly, a bit at a time on each jaw in turn. Final check was to hold a DTI against the centre, having unlocked the barrel clamp,and rotate the work, making any adjustments needed.
            Hah. No matter how much tooling I acquire/make I always need something else for the next project. Ok, I like these two ideas for this project, I think they will be accurate enough. I may try the one below first then verify using the method above or vise versa. Thanks for all the info!

            Originally posted by Toolguy View Post
            The old time way to do that is to make up a long flexible rod with a concentric point on it. Maybe 1/8" diam. X 12" long. Put the square end in the tailstock chuck and the pointed end in the punch mark on the work. Put a dial indicator on the side of the rod close to the workpiece. Turn the chuck and see how far the indicator needle moves. Adjust the chuck jaws to get a constant reading all the way around.

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            • #7
              Hi Les, Toolguy is bob on with his method, I use this regularly for a particular item I make, actually they are tumblers (hammers) for sidelock guns. These have a grunion on each side and I make out then centre punch with a optical centre punch then centre in the 4 jaw for each side, I leave one end oversize and finish gripping the other in a collet, this ensures concentricity but they are usually within .002 to .003 TIR out of the 4 jaw.
              A simple cheap method, just one point make sure the included angle of the point on your 1/8 rod is less then the incl angle on your centre punch. This ensures better location when setting up in the 4 jaw.
              Knowledge withheld is knowledge lost

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              • #8
                Tail stock mounted electron microscope with 50 inch HD monitor.

                Actually I like the thin, pointed rod and DI approach.
                Paul A.

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

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                • #9
                  Editing: Look like a missed previous posts in my haste to posy my own stuff End of edit:

                  Consider the trick John L Sullivan (old mentor - more later) taught me back when rocks were still soft:

                  1. File or grind a point on a skinny rod like a foot of bare 1/8 TIG rod.

                  2. Grip the end of the rod in the tailstock drill chuck,

                  3. Plug the point in the center punch mark so as the work rotates, the rod flexes to follow the punch mark,

                  4. Set the indicator contact on the rod.

                  5. Using the indicator readings, adjust the jaws to center the punch mark.

                  So long as the rod has a little push on it it will find the point of the punch markand from that you candial inthemark to the resolution of you indicator. But how accurately did you place the punch mark? If a hole location is so all-fired important have you considered toolmaker's buttons?

                  Nothing about the rod has to be accurate or hardened. The rod is a throw-away made quick on a bench grinder.

                  John called this the "pointed rod trick" and it's different from the wiggler as traditionally used from a rotating spindle. But you can use a wiggler in place of the pointed rod. I discourage this because the tip of the wiggler can be damanged from scrubbing in the punch mark and since the wiggler tip is short, attainable accuracy suffers proportionaltely. I learned this trick in 1968 and have passed it on countless times since so now I'm passing on John Sullivan's legacy to you guys.

                  Short bio: John L Sullivan was an old railroad machinist who could hardly read or write. He was 71 when I knew him in 1968. Wonderful kindly old grandfatherly guy, tall, skinny, and a little bent. Always wore pillow tick overalls and a grubby fedora hat. He liked my middle name so he called me "Cedric". Since John was nearly illiterate but knew a zillion old machine shop tricks and since I was a young guy who could read plans and shop paperwork he taught me his tricks and I 'splained his jobs and did his math. I don't know how John felt but I think I made out like a bandit.

                  I should probably mention he was a WWI, Banana War, and WW II Marine veteren (several hitches). a widower, deacon in his church, and long time Odd Fellow. He mined coal, was a farm laborer, but most of the time he was a round house machinist when he could find the work. He used to tell me horror stiries of failed shrinking loco wheel tires and repairing damage from train wrecks. I also got some recipes for welding rod coatings - he called it 'lectric welding rod - and the rod material was wire coat hangers - with variations. He had an FDR picture in his tool box along side family photos and had lost a fingertip in a union scuffle. Yeah, he was an interesting old dude and a hero to me.
                  Last edited by Forrest Addy; 10-19-2014, 08:48 PM.

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                  • #10
                    Don't use a full "point" as the end will engage with the small central "flat" (from the drill end) in the bottom of the "hole" - just leave a small flat end on the "rod" and the taper of the "rod" will engage the taper on the "hole".

                    Ideally the "cone" on the "rod should have a taper that is a bit larger than the "drilled hole".

                    Frankly if it were me I'd drill the holes on my pedestal drill up to a rod size allowing for later boring. Put the rod in the hole, locate it in the lathe with the dial indicator as before and start boring.

                    Its dead easy to locate a centre-punched hole with the drill end/tip and start drilling.

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                    • #11
                      This very crude and ugly but effective wiggler took me about 5 minutes to make using only a drill press (well and maybe a hacksaw and file). Sorry if the last pic is not too clear - it's looking at the pointy end that sticks in your punch mark. I think I dinged the rod with a hammer to make the ball a press fit at that spot. The rod is maybe 12" long, and you adjust the chuck until the far end of the rod is in line with the tailstock center. I have found it to be quicker than using a dial indicator.

                      ball on shaft

                      ball seat

                      assembled
                      "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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                      • #12
                        Just to be sure that no (minimum?) errors have crept in - scribe (calipers) a circle - any diameter - using the centre-punch hole (before drilling) as a check on the lathe before boring that all is OK 0 use a scriber/pointer (in the tool post) to check for any eccentricities that may have occurred and adjust to suit in the lathe chuck - before boring.

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                        • #13
                          Frank Ford's solution: http://www.frets.com/HomeShopTech/To...glycenter.html

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                          • #14
                            I just did this the other day. Needed to bore some holes for new servo motor mounts. (mill out of commission) Just scribed center lines and lined them up with a center in the tailstock. Worked out good. Franks method looks really good for more accuracy, thanks for sharing that

                            https://www.flickr.com/photos/csprecision

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                            • #15
                              Use a toolmakers button
                              Mark

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