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  • There HAS to be a better way...

    I have a truly beat to death 4 jaw chuck that came with my lathe, and which I've never used, until today. The job was to bore and thread a hole in a piece of 7075 aluminum 1" thick by 2" wide by 3" long, the hole was approx .720" and then threaded for 1/2"-14 pipe, about 1/4" from the the end in the 1" wide face. Took me FOREVER (well, all day, anyway) to get this piece dialed in, and I had to resort to some, well, lets just call my technique creative and move on. Not perfect by any stretch, but fortunately this is a project where good enough is.

    I've seen several fairly simple techniques for dialing in round stock with a 4 jaw, but what's the proper way to do it with a rectangular piece? And to make matters worse in this case, the jaw slots in the chuck were wider than the piece I was working on, which only added to the challenge. So what's the proper technique for this situation? Yes, I could have drilled, bored, and tapped the hole with my mill, but I don't have a boring head (yet), and the tap is a $50+ tool that I'd probably use only a couple of times. Besides, it's pretty much a certainty that I'm going to need to do something very similar sometime in the near future. Any help would be much appreciated.

    BTW, the piece came out very nice, but it's a good thing this is a hobby, if I had to make a living with what I did today, that would be a VERY expensive chunk of aluminum :-)! Later.

    Dave

  • #2
    when I had similar problems, I would use a parallels and/or 123 blocks on the face of the chuck between the jaws to hold the work parallel to the face of the chuck.

    Note: Put a sheet of wood or similar over your ways. 123 blocks falling out of the chuck can leave a nasty ding on the ways.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      layout, prick punch and centre with a wiggler, takes minutes. using an optical punch you'll be within a few though, if you need better, spot drill in the mill first, use the ball attachment on the wiggler and repeat...either way you have to get yerself a wiggler and you'll be minutes not hours

      Last edited by Mcgyver; 04-07-2012, 12:45 AM.
      .

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      • #4
        dykem the block. Lay out and mark lines. Put in 4 jaw. Adjust only jaws 180° apart. Rough both ways. Then finish by adjusting first set of jaws then second.

        Bob

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        • #5
          Does it have to be dead-on exact? I can get a piece dialed in to less than my indicator will show, given time and a good chuck. If it doesn't need to be perfect, I have a one-minute trick.

          Dykem and mark. Center drill on the mark if you want.

          Then chuck your pointed edgefinder (AKA centerfinder) in the tailstock. Use the four-jaw to indicate as you would in the mill.

          Voila, center to within a couple thou in about a minute.

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          • #6
            The method discussed above with the needle and indicator is a good one.

            I use a method that goes off the flat of the stock. Rotate the stock until the indicator is at the low spot. This will be where the stock is square to the axis of the indicator.

            You just adjust the stock in the 4 jaw until all 4 sides are reading the same low spot in the case of square stock. With rectangular stock, the opposing sides need to read the same.

            To get it off center, just loosen 1 jaw and move the stock with the opposing jaw, until your indicator reads the amount you need offset.

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            • #7
              Thanks, gents...

              Black Moons, I did use a parallel to keep it above the slots, glad to know that that's a "proper" technique :-).

              DM, just what I was looking for, and no, it doesn't have to be dead nuts. I actually thought about using the edge/center finder, but had already bored the initial 11/16" hole on the mill, after giving up on the 4 jaw the first time. Next time, and there will be a next time, this is a part for an airgun build, and I'll be doing at least one more, I'll do the entire operation on the lathe.

              On the subject of 4 jaw chucks, any suggestions for a decent replacement that won't break the bank? For the rare instances it'll get used, I don't need set-tru or 2 pc. jaws, just something that the jaws move easily on, what I have is hammered, perhaps literally, and almost needs a hammer to adjust it. Later.

              Dave

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              • #8
                Hi Dave,

                If you don't have moral objections to your money going half-way around the world, the Chinese "Fuerda" chucks I've seen / fitted have been consistently pretty good quality for their price (not the cheapest, but not up there with Bison etc.) - they can be a bit tight at first, but that beats loose and sloppy!

                Their 3-jaws generally make better than 2 thou" runout at the jaws, 4 thou" 4" out, which is not bad for a budget chuck, the 4-jaws are as good as you can dial 'em in and pretty good for concentricity

                Dave H. (the other one)
                Rules are for the obedience of fools, and the guidance of wise men.

                Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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                • #9
                  Looks like a job for a sticky pin and drilling machine.

                  MBB

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                  • #10
                    Originally posted by baldysm
                    The method discussed above with the needle and indicator is a good one.

                    I use a method that goes off the flat of the stock. Rotate the stock until the indicator is at the low spot. This will be where the stock is square to the axis of the indicator.

                    You just adjust the stock in the 4 jaw until all 4 sides are reading the same low spot in the case of square stock. With rectangular stock, the opposing sides need to read the same.

                    To get it off center, just loosen 1 jaw and move the stock with the opposing jaw, until your indicator reads the amount you need offset.
                    That is how I do it. I also move the carriage and make sure everything is strait as well.

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