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RE: [mlathemods] DIY Dividing Head Question

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  • Des Bromilow
    G Day, I have a worm/gear set I salvaged from a sewing machine that is also 24:1 and I m using that to make my first dividing head. I figure that if 24:1
    Message 1 of 6 , Feb 29, 2004
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      G'Day,

      I have a worm/gear set I salvaged from a sewing machine that is also
      24:1 and I'm using that to make my first dividing head. I figure that if
      24:1 proves to coarse for fine dividing, I can always use it to make a
      40:1, or 60:1 worm/gear set to replace it.

      I cannot speak on the issue of the work driving the indexer, BUT my
      design incorporates a brake on the spindle to prevent any issues of
      loading appearing on the worm. This isn't so much of an issue on my
      meaty 24:1 set, but a 60:1 based on a finer pitch would be more likely
      to strip, or jump a tooth.

      HTH
      Des

      -----Original Message-----
      From: e3pi [mailto:e3pi@...]
      Sent: Monday, 1 March 2004 2:00 PM
      To: mlathemods@yahoogroups.com
      Subject: [mlathemods] DIY Dividing Head Question


      I've zero experience with dividing heads, but I am excited with
      their 40: 60:1 precision leverage and ease for general dividing the
      circle; and possibly used for linear ruling too; I imagine.

      I've a Dayton 24:1 Gear Reducer.
      This has helical gears with negligial backlash that I can tell.

      It is small enough to be "Taigable".


      From reading I see 60:1; 40:1 are common for dividing head worm gears.

      Note also worm gears lock position on the non-"pinion" main gear
      axel - i.e.; the main gear angular displacement cannot drive the
      "pinion" or "worm" - which is a benefit for machinery set up.
      This Dayon gear reducer will drive either axel; i.e., 24:1 or 1:24;
      as desired. This could be a problem.


      One small grace advantage:

      "24" is a "highly composite" integer(24=4*3*2*1=4!); ; makes for easy
      arithmetic shared among common fractions of 360 degrees.

      So aside from half to a third the precision of other DH's - is this
      a reasonable source on the start of my first DIY dividing head?


      http://groups.yahoo.com/group/liveaboardlathe/message/81





      Yahoo! Groups Links






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    • xlch58@swbell.net
      While this is generally true, it is not precisely true. There are worm gear set ups that allow the worm the be driven by the othe gear. hey generally have a
      Message 2 of 6 , Mar 1, 2004
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        While this is generally true, it is not precisely true. There are worm
        gear set ups that allow the worm the be driven by the othe gear. hey
        generally have a large lead. If you think about it, with high accuracy
        parts and good lubrication just about any worm gear can work in reverse.


        Charles

        e3pi wrote:

        > Note also worm gears lock position on the non-"pinion" main gear
        > axel - i.e.; the main gear angular displacement cannot drive the
        > "pinion" or "worm" - which is a benefit for machinery set up.
      • James W. Early
        At our : Group there is a lot of information stored relating to rough and fine dividing as well as the making of
        Message 3 of 6 , Mar 1, 2004
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          At our :

          <http://groups.yahoo.com/group/mwmills2/>

          Group there is a lot of information stored relating to rough and fine
          dividing as well as the making of gears.
          JWE
          Long Beach, CA


          --- In mlathemods@yahoogroups.com, "e3pi" <e3pi@y...> wrote:
          >
          > I've zero experience with dividing heads, but I am excited with
          > their 40: 60:1 precision leverage and ease for general dividing the
          > circle; and possibly used for linear ruling too; I imagine.
          >
          > I've a Dayton 24:1 Gear Reducer.
          > This has helical gears with negligial backlash that I can tell.
          >
          > It is small enough to be "Taigable".
          >
          >
          > From reading I see 60:1; 40:1 are common for dividing head worm
          gears.
          >
          > Note also worm gears lock position on the non-"pinion" main gear
          > axel - i.e.; the main gear angular displacement cannot drive the
          > "pinion" or "worm" - which is a benefit for machinery set up.
          > This Dayon gear reducer will drive either axel; i.e., 24:1 or 1:24;
          > as desired. This could be a problem.
          >
          >
          > One small grace advantage:
          >
          > "24" is a "highly composite" integer(24=4*3*2*1=4!); ; makes for
          easy
          > arithmetic shared among common fractions of 360 degrees.
          >
          > So aside from half to a third the precision of other DH's - is this
          > a reasonable source on the start of my first DIY dividing head?
          >
          >
          > http://groups.yahoo.com/group/liveaboardlathe/message/81
        • e3pi
          Thank you all for your thoughtful replies. Repeatability seems an easy check by marking the axels and counting spins- or is there something else? DIY dividing
          Message 4 of 6 , Mar 1, 2004
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            Thank you all for your thoughtful replies.
            Repeatability seems an easy check by marking
            the axels and counting spins- or is there something else?

            DIY dividing head plates are discussed in some three
            internet links I've found.

            I'm again amazed at the depth and intensity of
            yahoo group esoteria - the link:

            http://groups.yahoo.com/group/mwmills2/

            with a big following suggests a new standard
            to me of good internet meat and potatoes.

            I'm a micro machinist newbie but have had good
            success cobbling disparate machines and salvaged
            minutiae into something new and delightful.

            My salvaged Hermes engrager alu "X" stand and steel compound
            carrying a Taig headstock into a Taig-scale milling
            machine is beautiful and I hope to have images
            in a week. Alot of options to hang units on; one
            advantage is the milling column dial is at the bottom,
            beneath the Taig lathe - keeping my hands furthest
            away from from a singing endmill or flycutter.

            The cockpit of my sloop that I fabricate in is
            a total tidal mess.


            e3pi
            http://groups.yahoo.com/group/liveaboardlathe/







            --- In mlathemods@yahoogroups.com, "James W. Early" <j.w.early@w...>
            wrote:
            > At our :
            >
            > <http://groups.yahoo.com/group/mwmills2/>
            >
            > Group there is a lot of information stored relating to rough and
            fine
            > dividing as well as the making of gears.
            > JWE
            > Long Beach, CA
            >
            >
            > --- In mlathemods@yahoogroups.com, "e3pi" <e3pi@y...> wrote:
            > >
            > > I've zero experience with dividing heads, but I am excited with
            > > their 40: 60:1 precision leverage and ease for general dividing
            the
            > > circle; and possibly used for linear ruling too; I imagine.
            > >
            > > I've a Dayton 24:1 Gear Reducer.
            > > This has helical gears with negligial backlash that I can tell.
            > >
            > > It is small enough to be "Taigable".
            > >
            > >
            > > From reading I see 60:1; 40:1 are common for dividing head worm
            > gears.
            > >
            > > Note also worm gears lock position on the non-"pinion" main gear
            > > axel - i.e.; the main gear angular displacement cannot drive the
            > > "pinion" or "worm" - which is a benefit for machinery set up.
            > > This Dayon gear reducer will drive either axel; i.e., 24:1 or
            1:24;
            > > as desired. This could be a problem.
            > >
            > >
            > > One small grace advantage:
            > >
            > > "24" is a "highly composite" integer(24=4*3*2*1=4!); ; makes for
            > easy
            > > arithmetic shared among common fractions of 360 degrees.
            > >
            > > So aside from half to a third the precision of other DH's - is
            this
            > > a reasonable source on the start of my first DIY dividing head?
            > >
            > >
            > > http://groups.yahoo.com/group/liveaboardlathe/message/81
          • sauer38h
            ... reverse. ... This is incorrect. A worm gear set with a locking ratio - which is nearly all of them - will strip before the worm will rotate under reverse
            Message 5 of 6 , Apr 13, 2004
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              --- In mlathemods@yahoogroups.com, xlch58@s... wrote:
              > If you think about it, with high accuracy
              > parts and good lubrication just about any worm gear can work in
              reverse.
              >



              This is incorrect. A worm gear set with a locking ratio - which is
              nearly all of them - will strip before the worm will rotate under
              reverse load no matter what the lubrication is. This is one of the
              useful features of worm gearing.

              Locking ratio worm gears have tooth contact at less than the locking
              angle. The locking angle varies with different materials and
              lubricants, but is never zero. Locking action occurs in worm gearing
              because the contact between teeth is entirely sliding contact -
              there's none of the rolling contact characteristic of spur gears with
              involute teeth. Spurs gears do not have locking ratios.

              The static coefficient of friction is the sine of the locking angle.
              It can be measured by putting a block of one material on a ramp of
              the other, and tipping the ramp up until the block slides under its
              own weight, or any other vertical force. The angle at which that
              happens is the locking angle. Strictly speaking, this is Coulomb
              or "dry" friction. The word dry is misleading - it does not mean
              unlubricated. It differentiates this friction mechanism from viscous
              drag, the domininant drag or "friction" force when a fully-developed
              hydrodynamic film separates the parts.

              Worm gears can be modified to be reversing by increasing the lead of
              the worm. To get enough lead you'd have to have something like a 4-
              tooth gear, which won't work for geometrical reasons. Some multi-lead
              worms can be reversed. They're not common - in thirty years in
              engineering I've yet to see one. The other way to make a reversing
              worm gear is to offset the axis of the worm and move it down toward
              the axis of the gear - in which case it becomes a spiroid or hypoid
              gear set, and isn't called a worm gear anymore.
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