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How do you center a square bar in a four jaw?

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  • How do you center a square bar in a four jaw?

    To All,
    how do you center and parralell a square bar in a four jaw chuck?
    Hilmar

  • #2
    Good evening and welcome, Hilmar. What you are requesting; can only be accomplished by a small Chinese man who currently resides in Germany, on Leek St.

    Comment


    • #3
      Centering stock

      Hi,

      This may not be the right way but works for me. I just did one today. What ever size I have, I draw or scribe lines on the diagonal. This shows the center. I then put a light punch mark in the diagonal center and using a center in the tail stock I bring the tail stock up to the part an align the block in the four jaw using the tail stock center. I find this works very well.

      Another way is to use a dial indicator, mounted on the cross slide and indicator one side then the opposite. Then get the other two sides the same way. This way works if the stock is finished. (good surface) You will have to lift the dial indicator stem off the stock each time, or move the cross slide out and back, being careful not to bump your dial indicator. This has worked for me also.

      Both methods get you very close. Not dead nuts.

      As to the face I indicate it also and using a small hammer I tap the piece into the chuck until it is as good as I can get it.

      Hope this helps. Good luck.
      Last edited by skeeter; 10-19-2006, 10:15 PM.
      skeeter

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      • #4
        Sometimes....people should acquire the skills of reading a technical publication. The old farts wrote them for a reason.

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        • #5
          H12721
          This is the way that I do it. I grind off the teeth on an old hacksaw blade. Clamp one end of the hacksaw in the tool post with the other end resting on the square stock that you have put in your four jaw.

          Rotate the stock and where the cornor of the stock lifts the blade to the highest point place the button of the indicator at that point and continue adjusting the stock untill you get an even indication all around.
          Don\'t ask me to do a dam thing, I\'m retired.
          http://home.earthlink.net/~kcprecision/

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          • #6
            Millman,
            Are you the only one born with a six inch scale in your mouth? That's besides the machinist on leek street.
            Kap

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            • #7
              Originally posted by Millman
              Sometimes....people should acquire the skills of reading a technical publication. The old farts wrote them for a reason.
              Maybe he prefers the old farts on this BBS, there seems to be plenty of them, and most of them don't mind helping out a noob.

              Comment


              • #8
                Charlie,

                VERY clever!

                Comment


                • #9
                  "This is the way that I do it. I grind off the teeth on an old hacksaw blade. Clamp one end of the hacksaw in the tool post with the other end resting on the square stock that you have put in your four jaw.

                  Rotate the stock and where the cornor of the stock lifts the blade to the highest point place the button of the indicator at that point and continue adjusting the stock untill you get an even indication all around."

                  Thats a neat idea, very clever - if i ever get a four jaw chuck i might just try it...


                  <Edit> second what Mike said! He got to it before i could!

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                  • #10
                    It is a shame when a new member is greeted in this manner. For this site to grow, it is in everybody's best interest to offer as much help as possible.

                    If you feel the best answer is to look it up in a book, a suggestion of appropriate books would be a much better reply.

                    This site is for the Home Shop Machinist, not the skilled journeyman.
                    Jim H.

                    Comment


                    • #11
                      I read the same technique as Charlie mentioned, either here or in one of the HSM magazines. Tried it several months later when trying to center an oddly shaped bar (like a "D" with a keyway) and then shortly after that with a chunk of rectangular aluminum bar (1" by 1.5") and it worked great.

                      For the roundish bar, I just got the best reading I could for the majority of the surface, and for the rectangular, I just had to get identical readings for the two pairs of sides. (Had to use a long-travel indicator though.)

                      The roundish bar ended up a frog hair off, the rectangular ended up dead nuts perfect.

                      Doc.
                      Doc's Machine. (Probably not what you expect.)

                      Comment


                      • #12
                        Amen

                        Jim, you said it just right. John

                        Comment


                        • #13
                          Hey now...I said Good evening and Welcome....what more do you want???

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                          • #14
                            Here's how I did it. It may be a bit tedious but after getting the hang of it it worked real well. I hope my memory is working just as well.
                            1) Eyeball the stock and get it close to centered as possible.
                            2) Mount a dial indicator to the compound rest so that it is parallel with the direction of the cross slide travel.
                            3) Place a level on the top of one of the surfaces of the stock or a jaw if the stock is narrow and adjust the chuck until it is level.
                            4) Advance the cross slide until the dial indicator contacts the stock plus a bit more.
                            5) Zero the dial indicator and cross slide.
                            6) Back the cross slide off enough to allow the stock to clear and rotate the chuck 180 degrees and level it.
                            7) Advance the cross slide untill you reach the zero reading on the cross slide dial.
                            8) Note the reading on the dial indicator. That will be the total offset.
                            9) Adjust the jaws on which ever side you need to half the total offset.
                            10) Double check by rotating and releveling 180 degrees. Make adjustments as needed until the dial indicator reads the same for both sides when the cross slide is at zero.
                            11) Do the same thing for the other sides and you should be able to dial that sucker in dead on.
                            I hope I remembered that right.
                            TS

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                            • #15
                              I setup a dial indicator with a disc tip and set the distance so the corners of the bar"bump" the disc like lobes on a camshaft.I think Charlie's method would be easier though so I think I'll try it!
                              I just need one more tool,just one!

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