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Small low tooth count gear question.

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  • Small low tooth count gear question.

    Brians "first gear" has got me to try making a gear for my first lathe, an Atlas 6", never use it any more but have had it for like 40 years, and would like to have it operational again.

    I read in a gear book I have where low tooth count on small gears requires additional consideration, nothing more just that.

    What additional consideration would that be referring to?

    This gear is an 8 tooth with about a .550 OD, it drives the carriage on the rack.

  • #2
    I think the consideration with those small tooth-count gears is you need quite a bit of undercutting at the base of the teeth....that wasn't a problem with those Craftsman lathes as the gears were cast. I seem to remember that those Craftsman lathes used 14.5*PA gears. As somebody mentioned on the other thread, anything under about 30 teeth at the 14.5 PA needs some undercutting.
    Jim

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    • #3
      Jim,
      You may have that right, there appears to be what i would call additional undercut on these teeth, these are not cast.

      Ken

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      • #4
        We need a picture Ken. 8 teeth is way below the practical limit for 14.5 pa gears.
        Free software for calculating bolt circles and similar: Click Here

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        • #5
          be back in a few, of what's left of them.

          Ken
          Last edited by Ken_Shea; 06-23-2010, 10:45 PM.

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          • #6
            Here it is Evan,

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            • #7
              THAT surely has the "undercut" showing in a lively manner...... the teeth look like spoons.

              THAT isn't going to be done with a regular circular gear cutter, it needs to be "generated".
              1601

              Keep eye on ball.
              Hashim Khan

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              • #8
                Pretty sad huh

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                • #9
                  Originally posted by J Tiers
                  THAT surely has the "undercut" showing in a lively manner...... the teeth look like spoons.

                  THAT isn't going to be done with a regular circular gear cutter, it needs to be "generated".

                  Not sure what generated means, I am thinking that it can be CNC'd on the mill, drill for the under cut and then use a 32nd end mill for the profile, if..... a 32nd end mill can be found with a 1/4" flute length.

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                  • #10
                    This might not help for that gear but John Stevenson helped me solve a low count gear problem.

                    go down to post # 23 in this thread.
                    http://bbs.homeshopmachinist.net/showthread.php?t=33136

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                    • #11
                      Not that I know much about gears, but the first thing that came to mind was to drill a ring of holes first to define the root, then cut the teeth. For only 8 teeth and very slow speed operation, you could file off any edges left after cutting the teeth to leave them all smooth. Should be good enough.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Originally posted by darryl
                        Not that I know much about gears, but the first thing that came to mind was to drill a ring of holes first to define the root, then cut the teeth. For only 8 teeth and very slow speed operation, you could file off any edges left after cutting the teeth to leave them all smooth. Should be good enough.
                        Yup...that occurred to me too...should work well enough
                        Jim

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                        • #13
                          Occurred to me too, see post #9

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                          • #14
                            Originally posted by Ken_Shea
                            Occurred to me too, see post #9
                            LOL...sorry, Ken, I missed that
                            Jim

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                            • #15
                              Originally posted by gary hart
                              This might not help for that gear but John Stevenson helped me solve a low count gear problem.

                              go down to post # 23 in this thread.
                              http://bbs.homeshopmachinist.net/showthread.php?t=33136
                              Thanks Gary,
                              Johns a pretty sharp cookie, man that was hard to get out

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