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  • Dividing Plates

    Hypothetical question as advertising isn't allowed on this board

    Using the standard Brown and Sharpe set of division plates certain numbers can't be done by direct indexing, like 63, 127 etc.

    Gert sells sets of generic plates that cover the standard numbers plus 63, 127 and 25 which does 125 divisions for dials etc.
    Now many people have the standard set which suits them fine and it's wasteful to buy another set but I was thinking about doing a stand alone plate to cover these non standard numbers.

    It's possible to get 7 or 8 rows of holes in and still have room for mounting holes, dowels etc. So taking 25, 63 and 127 as de-facto alternatives what other numbers would people like to see and for what reason ?

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  • #2
    I can't think of any specific ones but you might want to fool around with my DPLATES program, which will tell you what hole plates are needed to achieve all divisions up to some input maximum as a function of the DH gear ratio, e.g.,

    REQUIRED DIVIDING HEAD HOLE PLATES

    DH worm gear ratio [40] ?
    Maximum number of divisions needed [50] ?

    Hole plates required for all divisions up to 50
    4,5,6,17,19,21,23,27,29,31,33,37,39,41,43,47,49,
    Last edited by mklotz; 07-29-2007, 12:26 PM.
    Regards, Marv

    Home Shop Freeware - Tools for People Who Build Things
    http://www.myvirtualnetwork.com/mklotz

    Comment


    • #3
      Originally posted by mklotz
      you might want to fool around with my DPLATES program, which will tell you what hole plates are needed to achieve all divisions up to some input maximum as a function of the DH gear ratio, e.g.,

      REQUIRED DIVIDING HEAD HOLE PLATES

      DH worm gear ratio [40] ?
      Maximum number of divisions needed [50] ?

      Hole plates required for all divisions up to 50
      4,5,6, 17,19,21,23,27,29,31,33,37,39,41,43,47,49,
      Marv,

      I was going to send you an email about this.

      John and I have been exchanging email about having him CNC drill a set of "high number" dividing plates for my Ellis, and I was trying to use your program to add a couple of extra rows to the OEM dividing plates (the subject of John's post).

      The problem is that there are several ways to get the desired number of divisors. I tracked down the numbers on the rings for the various 40:1 and 90:1 dividing heads, and they're almost all different.

      What would help a lot is if your program could add two features:

      1. Take the natural dividing ratio of the specified worm gear into account on the output. For example, your program indicates that you need 4 and 6 divisor rings, but no one makes dividing plates with those numbers because they're even multiples of the worm gear.

      2. Favor prime numbers in the output. This gives the most divisors with the least number of dividing rings (chords of holes on the dividing plates).

      Thanks!

      Robert
      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

      Comment


      • #4
        Dividing plates

        Currently, one set of 3 4" plates to fit the GH Thomas were rusty following my move 6 years ago. They were made by me but I could do with a tidier set.
        I am a bit stuck for space, time and material now.

        Again, I would like a set to go on my a future headstock dividing attachment to my Myford Super 7. It's a lot of work this piece of kit and I ain't getting any younger.

        Does the Hon. Lady Gert create such 'lace work' as we are not allowed to talk about mundane money matters here?

        And I am still trying to get my DRO set up on my mill and all those things from Harrogate on my Myford - and I need afternoon snatches of shut eye.

        Please Sir

        Nodding Off Norm

        Comment


        • #5
          Originally posted by aviemoron
          Currently, one set of 3 4" plates to fit the GH Thomas were rusty following my move 6 years ago. They were made by me but I could do with a tidier set.
          Hi Norm, stating the obvious: they're just holes in a metal plate! Just scrub 'em with PBlaster and some steel wool, and they'll be good as new

          Hope you're feeling well! I've got some T&C Grinder pictures I need to send you...

          Cheers,

          Robert
          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

          Comment


          • #6
            Robert wrote:

            ------------------------------------------------------------

            What would help a lot is if your program could add two features:

            1. Take the natural dividing ratio of the specified worm gear into account on the output. For example, your program indicates that you need 4 and 6 divisor rings, but no one makes dividing plates with those numbers because they're even multiples of the worm gear.

            2. Favor prime numbers in the output. This gives the most divisors with the least number of dividing rings (chords of holes on the dividing plates).

            -------------------------------------------------------------

            I suppose I shouldn't have labeled the program output "hole plates required".
            What those numbers signify is the number of divisions of a full DH *crank* rotation needed to get all the divisions up to 50. "4" means you need some way to reliably turn the crank through 1/4 turn. "6" means a way to turn the crank 1/6 of a rotation, etc.. I'm well aware that nobody makes 4 or 6 hole plates. But any hole circle that will produce 1/4 or 1/6 of a *crank* rotation will do. (A 24 hole circle will produce both.)

            I don't understand your point #2. The outputs are dictated by the mathematics. There is no option for the program to favor anything. OTOH, the individual constructing plates can use any (integer) multiples of the indicated numbers. The only requirement is that one be able to rotate the DH crank through the divisions indicated in the output.
            Regards, Marv

            Home Shop Freeware - Tools for People Who Build Things
            http://www.myvirtualnetwork.com/mklotz

            Comment


            • #7
              Originally posted by lazlo
              Marv,

              I was going to send you an email about this.

              John and I have been exchanging email about having him CNC drill a set of "high number" dividing plates for my Ellis...

              Thanks!

              Robert
              That's nifty. I'd buy a set. I also have an Ellis. I need a 7 for making a model of a radial engine.

              Lee.

              BTW Lazlo did you get my PM?

              Comment


              • #8
                Originally posted by Lee in Texas
                I need a 7 for making a model of a radial engine.

                Lee.
                Any integer multiple of 7 will work.
                Regards, Marv

                Home Shop Freeware - Tools for People Who Build Things
                http://www.myvirtualnetwork.com/mklotz

                Comment


                • #9
                  Originally posted by mklotz
                  What those numbers signify is the number of divisions of a full DH *crank* rotation needed to get all the divisions up to 50. "4" means you need some way to reliably turn the crank through 1/4 turn. "6" means a way to turn the crank 1/6 of a rotation, etc.. I'm well aware that nobody makes 4 or 6 hole plates. But any hole circle that will produce 1/4 or 1/6 of a *crank* rotation will do. (A 24 hole circle will produce both.)
                  That's the problem -- the output of your program needs a lot of interpretation. For example, if you type in a 40:1 worm gear, and 100 divisions, your program returns:

                  8, 12, 15, 37, 39, 41, 43, 47, 49, 51, 53, 57, 59, 61, 63, 67, 69, 71, 73, 77, 79, 81, 83, 87, 89, 91, 93, 97, 99

                  Those don't match any set of dividing plates (Ellis, Brown and Sharpe, Grizzly, ..., because they're not the recommended dividing plate holes: they're the DIV and MOD of all the integers from 1 to the number of dividers you requested.

                  So to figure out what dividing plates you need, you have to walk through those numbers and come up with the number of holes that can be used as the least common denominator for the most number of those divisors from your program. As it turns out, those most-commonly used LCD's are the prime numbers.

                  For example, these are the Ellis dividing plate numbers for a 40:1 worm gear

                  Ellis Dividing Plates:

                  #1: 15, 16, 17, 18, 19, 20
                  #2: 21, 23, 27, 29, 31, 33
                  #3: 37, 39, 41, 43, 47, 49

                  The primes in that set are 17, 19, 23, 29, 31, 37, 41, 43, 47 -- in other words, a set of dividing plates has to have those numbers, so those numbers are common to all plates (whether 40:1 or 90:1).

                  After you pick those numbers and eliminate all the combinations of divisors they give, then you play with the remaining numbers to get the most number of divisors with the least number of dividing rings.

                  I've got a spreadsheet halfway completed that does this for you, but it would be a lot easier to write it in 'C'.
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                  Comment


                  • #10
                    Originally posted by John Stevenson
                    So taking 25, 63 and 127 as de-facto alternatives what other numbers would people like to see and for what reason?
                    Possibly 71 and 113 for a pi-approximating geartrain.

                    Comment


                    • #11
                      Originally posted by djc
                      Possibly 71 and 113 for a pi-approximating geartrain.
                      63/40 is a more accurate approximation of Pi than most toolroom lathe leadscrews. But if you really want a mathematically perfect conversion gear, why not go for the 127 tooth gear instead of the 113 approximation? The difference in gear circumferences is negligible.

                      Just a thought...
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                      Comment


                      • #12
                        How about something that will divide 250 divisions Some machine dials are ¼ per turn.Also van norman had plates with,57,59 holes would be nice.
                        Every Mans Work Is A Portrait of Him Self
                        http://sites.google.com/site/machinistsite/TWO-BUDDIES
                        http://s178.photobucket.com/user/lan...?sort=3&page=1

                        Comment


                        • #13
                          Originally posted by lane
                          How about something that will divide 250 divisions Some machine dials are ¼ per turn.
                          You can get 250 with the 25 hole plate that John had on his non-standard list: 25, 63 and 127.

                          25 is on the Brown & Sharpe and Ellis "High Division Plates", which give you all divisors up to 100, all the even divisors up to 200, and almost all non-prime divisors up to 250:

                          B&S/Ellis High Number Plates:
                          #4: 25, 61, 71, 83, 91, 93
                          #5: 51, 53, 63, 73, 81, 96
                          #6: 22, 57, 67, 77, 87, 97
                          #7: 28, 59, 69, 79, 89, 99

                          Also van norman had plates with 57, 59 holes would be nice.
                          See the blue numbers in the B&S/Ellis plates above. Lane, could you list the plate numbers for the Van Norman dividing head? Isn't that a differential dividing head (which means it didn't need that many plates)? What's the worm gear in the Van Norman?
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                          Comment


                          • #14
                            My small L&W dividing head came with three plates:
                            15, 16, 17, 18, 19, 20
                            21, 23, 27, 29, 31, 33
                            37, 39, 41, 43, 47, 49

                            I don't know if there were other plates. I believe it has a 40:1 ratio.

                            Greg

                            Comment


                            • #15
                              Ditto for mine, aside from the "came with" part, as I had to find two of them. But those two came with a tailstock, so it was worth it.

                              Same set as for B&S and for the same reason. It is 40:1, at least if it is the 6" swing size (3" off table).
                              1601

                              Keep eye on ball.
                              Hashim Khan

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