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Indicating a rotary table

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  • #16
    Originally posted by nickel-city-fab View Post
    I don't yet have a mill, but I've wondered for the longest time about making a "double ended" bar, with one end to fit the mill spindle, and the other end to fit the center hole in the rotary table. That sounds like a good job to do between dead centers.
    That's an interesting idea. If you try this keep in mind that you don't need full length shapes on both ends. Plus that would require a LOT of room to allow it to be set in place and then removed. A half length MT to fit the table center hole, assuming it has an MT center like my table does, would be enough to stabilize the arbor. And then just a rounded corner that sticks up into the taper of the mill's spindle to self center the table would be enough. No need for a full R8 form with draw bar and all. And the resulting setup tool would be quite short. Removal would demand that the setup tool have a shoulder that a couple of pry bars could get under. Or perhaps a threaded collar that would screw down against the socket of the rotab and pop the taper free. After all with this setup bar in the table there's no way to bump it free from behind. You'd need some way to do this from the face side since at that point it's bolted down to the mill's table.

    Alternatively a full R8 with draw bar hole and just a nose with about 1/4" worth of MTx size taper that fits just into the upper opening would draw the table into center but not require a lot of height to back off for removal of the setting tool. And the table or quill would give you the leverage needed to bump the short bit of taper free.

    To make up for any play I'm thinking that the table would be pulled into position then give the table a few little twists to let everything sort of ease into the last thou or so for centering and then while the LIGHT centering pressure is maintained the rotab is secured, Then the setting tool is extracted, table or head shifted back to allow the tool to be withdrawn and work carries on. And all in all I'm rather liking the idea of the MT half stub with threaded retraction collar and just a short portion of a matching R8 nose taper that goes up into the spindle.

    Chilliwack BC, Canada

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    • #17
      I would go with a full R8 and a stubby Morse about an inch long. You could just get an R8 blank and turn the end instead of boring it like normal. Definitely a between centers job though.

      There actually is a new taper but I can't remember the name of it, which is a stubby morse. I've seen it on chinese chucks, I think it was called "B16" or something like that.

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      • #18
        It's not a bad idea for a "quick jab" ----------- I always squirt LPS-3 on the mills table and glide the RT around on it first before anchoring so if you did what you said it would self align nicely with just a little quill pressure... it's a good idea and im sure after a few "double checks" with an indicator would build enough confidence to not worry it's going to be too far off..

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        • #19
          Originally posted by nickel-city-fab View Post

          I think I know the video you mean. I always figured it was the hole that matters (especially if its tapered) because thats where the centerline is.
          Shouldn't that be "that is where the centerline is suppose to be". The hole should be right on the centre of the table BUT that doesn't mean it is, so indicating the spindle will line the
          'centre of rotation" of the the table up with the spindle. Yes or no.
          The shortest distance between two points is a circle of infinite diameter.

          Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

          Southwestern Ontario. Canada

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          • #20
            Originally posted by loose nut View Post

            Shouldn't that be "that is where the centerline is suppose to be". The hole should be right on the centre of the table BUT that doesn't mean it is, so indicating the spindle will line the
            'centre of rotation" of the the table up with the spindle. Yes or no.
            If I understand what you mean (not sure I'm followin you) yes it is possible that the hole is off center, or non-round, or even tilted. I would think that indicating off the hole will line it up on its centre regardless of what the OD is doing, for both the spindle *and* the table. Even if the hole is incorrect, it still has a centre, and you want both of those centres to line up, right? Regardless of what anything else is doing.

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            • #21
              If you centre the hole and it is off the table rotational centre then the hole centre will spin around the spindle centre in a circle instead of just rotating in place. I think the point that Joe Pie made was you want the table rotational centre to be under the spindle centre weather it is aligned to the hole or not.
              The shortest distance between two points is a circle of infinite diameter.

              Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

              Southwestern Ontario. Canada

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              • #22
                Originally posted by loose nut View Post
                If you centre the hole and it is off the table rotational centre then the hole centre will spin around the spindle centre in a circle instead of just rotating in place. I think the point that Joe Pie made was you want the table rotational centre to be under the spindle centre weather it is aligned to the hole or not.
                OK, my brain is exploding. I gotta think about it some, but I have a feeling we're actually saying the same thing in different ways. Gonna have to sleep on it, brain fade.

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