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How do I cut a spiral groove in a flat face plate.

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  • hglent
    I have a older 12 Craftsman in fairly good shape. I would like to cut a spiral groove in to a aluminum disk about 3 inches in diameter. Just guessing I will
    Message 1 of 6 , Oct 1, 2011
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      I have a older 12" Craftsman in fairly good shape.

      I would like to cut a spiral groove in to a aluminum disk about 3 inches in diameter. Just guessing I will need about 6 spirals. Just a guess!

      I am not a pro like most of you are so be easy on me when you tell me I'm nuts!

      Paul K.
      HGLENT
    • Russ Kepler
      ... OK, 3 diameter is 1.5 radius, and 6 grooves means a spacing of .25 . You ll want to check this but I think the crossfeed is 2x the longitudinal feed so
      Message 2 of 6 , Oct 1, 2011
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        On Saturday 01 October 2011 "hglent" <hglent@...> wrote:
        > I have a older 12" Craftsman in fairly good shape.
        >
        > I would like to cut a spiral groove in to a aluminum disk about 3 inches in
        > diameter. Just guessing I will need about 6 spirals. Just a guess!

        OK, 3" diameter is 1.5" radius, and 6 grooves means a spacing of .25". You'll
        want to check this but I think the crossfeed is 2x the longitudinal feed so
        you should be able to gear things for 8tpi, setup the tool at the edge of the
        disk on center and engage the crossfeed for the spiral.

        Check it out in advance and it it looks like it'd work run things slowly. I'd
        also try to either get all the cut done on the first pass or to leave the feed
        fully engaged in the hopes that the next cut starts in the same place - but
        I'm none too sure that it would.

        > I am not a pro like most of you are so be easy on me when you tell me I'm
        > nuts!

        I think you could do this, as long as you're looking for something more
        decorative and not the scroll for a chuck or something.
      • Jon Elson
        ... First, the very oldest 12 (like the 10 D model) had no power crossfeed. ... No, I think the Atlas has 1:1 between threading pitch and facing pitch. So,
        Message 3 of 6 , Oct 1, 2011
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          Russ Kepler wrote:
          > On Saturday 01 October 2011 "hglent" <hglent@...> wrote:
          >
          >> I have a older 12" Craftsman in fairly good shape.
          >>
          First, the very oldest 12" (like the 10" D model) had no power crossfeed.
          >> I would like to cut a spiral groove in to a aluminum disk about 3 inches in
          >> diameter. Just guessing I will need about 6 spirals. Just a guess!
          >>
          >
          > OK, 3" diameter is 1.5" radius, and 6 grooves means a spacing of .25". You'll
          > want to check this but I think the crossfeed is 2x the longitudinal feed so
          > you should be able to gear things for 8tpi, setup the tool at the edge of the
          > disk on center and engage the crossfeed for the spiral.
          >
          No, I think the Atlas has 1:1 between threading pitch and facing pitch.
          So, it should need
          4 TPI setting. But, of course, the OP should check the settings
          carefully before starting
          cutting.

          The problem is this will have the leadscrew spinning so fast that it may
          well overload the
          gear train. I did a job like this once, and ended up powering the lathe
          manually, as I was
          afraid of breaking the gear train. The other way would be to put a
          Dremel or similar
          spindle on the toolpost, and mill the groove rather than cut it.

          You could actually power the spindle from the crossfeed handle.
          > Check it out in advance and it it looks like it'd work run things slowly. I'd
          > also try to either get all the cut done on the first pass or to leave the feed
          > fully engaged in the hopes that the next cut starts in the same place - but
          > I'm none too sure that it would.
          >
          No, unless the groove is just a very shallow scratch, you won't be able
          to do it in one
          pass. With a careful study of the gear train, you might be able to
          figure out how to
          disengage and re-engage. For threading, you have the threading dial,
          but there's no
          such device on the crossfeed. So, I think you have to retract the tool
          and back up
          the spindle for the next pass.

          Jon
        • Michael Fagan
          I would definitely look into milling the groove while rotating the spindle by hand. Sent from a mobile device. ... in ... You ll ... so ... the ... I d ...
          Message 4 of 6 , Oct 1, 2011
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            I would definitely look into milling the groove while rotating the spindle
            by hand.

            Sent from a mobile device.
            On Oct 1, 2011 12:57 PM, "Jon Elson" <elson@...> wrote:
            > Russ Kepler wrote:
            >> On Saturday 01 October 2011 "hglent" <hglent@...> wrote:
            >>
            >>> I have a older 12" Craftsman in fairly good shape.
            >>>
            > First, the very oldest 12" (like the 10" D model) had no power crossfeed.
            >>> I would like to cut a spiral groove in to a aluminum disk about 3 inches
            in
            >>> diameter. Just guessing I will need about 6 spirals. Just a guess!
            >>>
            >>
            >> OK, 3" diameter is 1.5" radius, and 6 grooves means a spacing of .25".
            You'll
            >> want to check this but I think the crossfeed is 2x the longitudinal feed
            so
            >> you should be able to gear things for 8tpi, setup the tool at the edge of
            the
            >> disk on center and engage the crossfeed for the spiral.
            >>
            > No, I think the Atlas has 1:1 between threading pitch and facing pitch.
            > So, it should need
            > 4 TPI setting. But, of course, the OP should check the settings
            > carefully before starting
            > cutting.
            >
            > The problem is this will have the leadscrew spinning so fast that it may
            > well overload the
            > gear train. I did a job like this once, and ended up powering the lathe
            > manually, as I was
            > afraid of breaking the gear train. The other way would be to put a
            > Dremel or similar
            > spindle on the toolpost, and mill the groove rather than cut it.
            >
            > You could actually power the spindle from the crossfeed handle.
            >> Check it out in advance and it it looks like it'd work run things slowly.
            I'd
            >> also try to either get all the cut done on the first pass or to leave the
            feed
            >> fully engaged in the hopes that the next cut starts in the same place -
            but
            >> I'm none too sure that it would.
            >>
            > No, unless the groove is just a very shallow scratch, you won't be able
            > to do it in one
            > pass. With a careful study of the gear train, you might be able to
            > figure out how to
            > disengage and re-engage. For threading, you have the threading dial,
            > but there's no
            > such device on the crossfeed. So, I think you have to retract the tool
            > and back up
            > the spindle for the next pass.
            >
            > Jon


            [Non-text portions of this message have been removed]
          • Paul
            OOOOP! I forgot to mention this old lathe does not have a powered cross feed. Just me turning the handle. So I conclude I am dead in the water, and will need
            Message 5 of 6 , Oct 2, 2011
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              OOOOP!

              I forgot to mention this old lathe does not have a powered cross feed.
              Just me turning the handle. So I conclude I am dead in the water, and
              will need to find a shop to do this for me.

              Sorry for not being clear in my first post.

              Paul K.
              HGLENT
            • Rexarino
              Paul, what kind of accuracy do you need, and how important is the finished shape of the groove? If you can make an initial groove deep enough to follow with a
              Message 6 of 6 , Oct 2, 2011
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                Paul, what kind of accuracy do you need, and how important is the finished
                shape of the groove?

                If you can make an initial groove deep enough to follow with a tool, you can
                carve this out with a hand held lathe tool in a similar fashion to
                woodworkers gouges. It's not generally done by any one but watchmakers, but
                aluminum can be cut with a hand held tool, and using a smooth bottom tool
                with a long handle sliding on a smooth support, you can follow an
                established groove and enlarge it. You would configure the tool to have
                only a few degrees of front rake and top rake, and make it of a shape that
                can follow the increasing radius of the spiral, perhaps a half circle. It
                would have a long handle for leverage, and the support would be very rigid
                and as close to the disk as possible. The shape of the tool could be made
                so it followed the previous cut and created the correct groove.

                The resulting accuracy would be dependent on the first groove cut. If I
                were determined to make it myself, I'd use a non stretchy rope wrapped
                thrice around the correct size high-friction-surface drum on a cross feed
                extension, pulley'd for a right turn then to wrap thrice around the
                temporary high-friction-surface spindle drum, and my willing assistants
                would maintain pressure on the ends of the rope and guide it while I cranked
                the initial pass, perhaps with a router jury rigged to the cross feed table
                to create a Vee or square groove on my one initial pass.

                Because the rope length varies as you wind on different parts of the drum,
                the groove will have small inaccuracies.

                A better level of accuracy could be built from belt and gear drives to link
                the cross feed and spindle, and would probably let you make repeated cuts as
                long as you avoid slippage in the gear/belt train and always cut in the same
                direction, avoiding backlash. A belt drive with twisted belt corners might
                have rather good accuracy at hand-crank speeds. The belt would change
                direction with corner pulleys, similar to the old Corvair generator belt or
                the twisted belt on riding lawnmower decks.

                A worm and pinion could be connected to drive the the spindle from the cross
                feed, but would need a splined shaft to accommodate the movement in the
                cross slide.

                Rex



                On Sun, Oct 2, 2011 at 8:18 AM, Paul <hglent@...> wrote:

                > OOOOP!
                >
                > I forgot to mention this old lathe does not have a powered cross feed.
                > Just me turning the handle. So I conclude I am dead in the water, and
                > will need to find a shop to do this for me.
                >
                > Sorry for not being clear in my first post.
                >
                > Paul K.
                > HGLENT
                >
                >
                >
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