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Novel way to center work in a 4jaw chuck.

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  • #31
    this place is getting as rude as P.M.!

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    • #32
      Ever since I started using a four jaw chuck, about 12 years ago, I have used a 1/4" diameter rod x 15" long with a point turned on one end. The pointed end is placed into a "center punch mark" on the piece I want to center in the four jaw chuck, and the other end is held in a tailstock mounted chuck. Then a dial indicator is brought in to bear on the 1/4" rod just clear of the part in the chuck, and the chuck is turned by hand and adjusted ---and adjusted---and adjusted---until the dial indicator reads "0" for a full 360 degrees of rotation. This method has served me well, but about 3 months ago I wanted to center a piece which had a 3/8" hole that I wanted to bore out to marginally oversize. I didn't want to use a larger diameter rod, because the larger in diameter the rod is, the less willing it is to flex. I thought about it for a while and then come up with this modification to my 1/4" diameter rod. This works great, the rod can still deflect easily, and I can center accurately on holes up to 9/16" diameter. Note that in order to do this, you can't use the typical pointed end on a dial indicator. It has to be unscrewed and replaced by a larger, flat "anvil" on the end


      Last edited by brian Rupnow; 01-23-2021, 04:46 PM.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • #33
        I just centered a piece in my 4 jaw using the method described by JDunmyer---It was an absolute treat. Much quicker than anything I have tried before.

        Center by eye first, then put your indicator against the part. Rotate by hand, noting "high" and "low" readings. Rotate so the reading is halfway between the two, then zero the indicator. Rotate the part until a jaw is lined up with the indicator plunger. Adjust that jaw and the one opposite until indicator reads Zero. Rotate 1/4 turn until another jaw is under the indicator plunger, adjust that jaw and the one opposite until indicator reads Zero. Rotate chuck one turn to verify centering, you should be very close, if not right on.
        Last edited by brian Rupnow; 01-24-2021, 11:12 AM.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #34
          Good for you! I would have posted about it myself but I expected that was how everybody did it! Been doing it that way so long that it didn't even occur to me that it would be something novel to anyone.

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          • #35
            I do what Mr Rupnow does, only I adjust to half the overall indication.... usually close
            2801 3147 6749 8779 4900 4900 4900

            Keep eye on ball.
            Hashim Khan


            It's just a box of rain, I don't know who put it there.

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            • #36
              I’m going to share a method my dad showed me and it works really well. Running a 32” machine with a 24” chuck using two chuck wrenches is impossible and using a wobble arm are pretty lame methods in my opinion.
              This a temporary solution so that members can experiment and see if they like it and if it works for you the markings need to be made permanent.
              First rule the jaws have to stay in their respective slots and this is where the permanent marking will come into play if you adopt this.
              Chuck up a round piece of stock and indicate it running true and straight. Now use a sharpie or something and mark the jaw screw face so they are clocked the same. I.E. a dot or line at say 12 o’clock.
              Now remove the stock and put in another piece of different size run the jaws so they are about the same distance from the lines on the face of the chuck, usually you can do this and be within one turn of the jaw screw. Now turn the jaw screws in the appropriate direction so that the marks you put on the jaw screw are clocked identical, the piece should be purty close to true, I usually get within .010” or under.
              This will work on square, rectangular or out of round stock as well. Square stock the alignment marks will be clocked the same, on rectangular the alignment marks will be the same on 1 and 3 but probably different from 2 and 4

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              • #37
                That's not the first time I've been accused of using "rather lame methods.". You should talk to some of my old girlfriends!!!---Brian
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • #38
                  Now, something different, from a new member. I'll bet this idea could lead to other ways of adjusting a 4 jaw, that most of us never thought about. Since this idea came from Btovin83 father, this could have been a popular way of getting the job done in the past.

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                  • #39
                    It's like follow the dots once you get used to it.

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                    • #40
                      As soon as we have a warm day in my garage, I want measure how far a jaw will advance or retard With one turn of the adjustment screw. If the jaw movement is in even numbers, you could move to any size, from a fixed starting possition by calculating the number of turns to get the measurement you want.

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                      • #41
                        Do it everyday for years on end and it becomes fast, simple and utterly boring (no pun intended).



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                        • #42
                          Theres something wrong with this thread, most of the replies are connected with the original theme.

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                          • #43
                            Give it time.

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                            • #44
                              Brian it sounds like you are pretty much set on your method but how do you handle square stock or rectangular stock, especially tubing. I had to face to length some 36" long 2" square tubes. Using the method of marking the jaw screws I didn't even bother to dial indicate the chuck end as usually it will be under .010" TIR. Clue me in as I'm open to a better way.

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                              • #45
                                If facing off square or rectangular tube, does it really matter if it is in center or not?

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