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What Could Have Moved Here???????

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  • #31
    I would think a boring bar would work for the grooves.



    A small one with a curved cutting tip:

    Last edited by PStechPaul; 10-19-2016, 01:58 AM.
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

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    • #32
      A boring bar will only cut one side of the groove wall and would have to be flipped upside down and the spindle run in reverse to cut the opposite or inside groove wall and you can't cut across the entire bottom of the groove which has to be flat. A square tool bit will do all that, just have to be careful when you contact the bottom or it will start to chatter.

      JL...............

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      • #33
        I'll mention one possibility that no one else has - if you get the work pretty hot it'll expand against the chuck jaws and on cooling could be just a little loose as the aluminum will have shifted a little bit where it's in contact. That plus the 6 jaw "opposing grip" might add up to the shift that you saw.

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        • #34
          Joel, I'm thinking that in this case perhaps a rectangular tool standing on edge with the correct reliefs ground into the end might have been a nice option. The added height would give it a little more support to resist the chatter.

          It certainly would still be an issue and I'm with you about keeping the flat end fairly narrow to try to avoid the issue as much as is practical.
          Chilliwack BC, Canada

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          • #35
            Well first off the round never got hot, not even warm. It would take quite a bit of heat to warm up a round of that size to where expansion would be a problem.
            I hate to have to do these over again, perhaps I should have use a better steel like 1144.
            I chucked both of these up and indicated all the surfaces for concentricity, the most I saw in variance on the 4" hub was about .0015 and on the 3" hub the center hole was out by .003
            I wanted to keep these as perfect as I could for balance reasons. I know my machine will do a lot better than .003. I would have been happy with .0005.
            I'm not sure if this will make any difference or not since the grinding wheels will be balanced as an assy. with the hub. But there is still that eccentricity factor, not sure if balance corrects that, or if eccentricity will cause vibration even though everything is balanced.

            JL.............

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            • #36
              Originally posted by BCRider View Post
              Joel, I'm thinking that in this case perhaps a rectangular tool standing on edge with the correct reliefs ground into the end might have been a nice option. The added height would give it a little more support to resist the chatter.

              It certainly would still be an issue and I'm with you about keeping the flat end fairly narrow to try to avoid the issue as much as is practical.
              I think the chatter is a combination of the tool post, cross slide and everything else involved. The tool bit was only sticking out of the holder about 3/4".

              JL.............

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              • #37
                Originally posted by JoeLee View Post
                I'm not sure if this will make any difference or not since the grinding wheels will be balanced as an assy. with the hub. But there is still that eccentricity factor, not sure if balance corrects that, or if eccentricity will cause vibration even though everything is balanced.
                Doesn't make any difference if you are balancing them. Just balance them on their own first, so the wheel wear doesn't affect the center of gravity of the assembly.
                Amount of experience is in direct proportion to the value of broken equipment.

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