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  • Indexing Plates

    I have noticed a variety of articles over the years that show how to make your own indexing heads and plates. I am set up for doing the actual work but I don't know what constitutes a set of "standard" indexing plates. There appears to be a standard set of three. Does anyone know if this is true and if so what hole circles are on each plate in a standard set.

    Nathan

  • #2
    Hi
    your standerd set is for 3,4,6,12. hole patterns you can make one plate to do a number of things. but the key is are you going to make gears or drill holes with your indexer. if you are going to make gears you need o lot more spaces 36 gives you 10 deg's. so think about what you are going to do with it and remember you can alwas make more plates. hope that help's

    Comment


    • #3
      <font face="Verdana, Arial" size="2">Originally posted by nmdeselle:
      I have noticed a variety of articles over the years that show how to make your own indexing heads and plates. I am set up for doing the actual work but I don't know what constitutes a set of "standard" indexing plates. There appears to be a standard set of three. Does anyone know if this is true and if so what hole circles are on each plate in a standard set.

      Nathan
      </font>
      Standard set known as Browne and Sharpe set is three plates.
      Plate 1 has :- 15,16,17,18,19,20
      Plate 2 has :- 21,23,27,29,31,33
      Plate 3 has :- 37,39,41,43,47,49

      These are normally used in conjunction with a 40:1 worm and wheel.




      ------------------
      Regards,
      John Stevenson,
      Nottingham, England
      .

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



      Comment


      • #4
        The article is already very old, but I still want to contribute something.


        To use a worm and worm wheel with 60 teeth, I use the following sets with bolt circles.

        Plate 1: has 27; 32; 42; 50; 66; 78;
        Plate 2: has 29; 31; 34; 38; 46; 60;
        Plate 3: has 37; 41; 43; 47; 49; 53;

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        The outer diameter of the dividing discs is 4 inch or ~ 100mm .
        Many greetings from the southwest of Germany.
        Bruno
        http://www.mueller-bruno.de

        Comment


        • #5
          Originally posted by Bruno Mueller View Post
          The article is already very old, but I still want to contribute something.


          To use a worm and worm wheel with 60 teeth, I use the following sets with bolt circles.

          Plate 1: has 27; 32; 42; 50; 66; 78;
          Plate 2: has 29; 31; 34; 38; 46; 60;
          Plate 3: has 37; 41; 43; 47; 49; 53;

          The outer diameter of the dividing discs is 4 inch or ~ 100mm .
          Bruno -- Thank you!

          That looks like the set of plates for George H. Thomas' "versatile Dividing Head", is that true? I am trying to make the same thing, but I don't have any of his castings or materials -- I do have two gears with 60 teeth each.
          25 miles north of Buffalo NY, USA

          Comment


          • #6
            Bruno, you may want to slow right down for your countersinking... and or may need a fresh countersink... of course what you have will work as is.

            Comment


            • #7
              Included with my DIVHEAD archive is a program, DPLATES, that will calculate hole sequences needed to produce any division up to a maximum value input by the user. A sample output is shown below. Of course, some of the required hole sequences can be combined into a single hole circle on a plate, e.g. 5 and 8 could be combined into a single 40 hole circle.

              REQUIRED DIVIDING HEAD HOLE PLATES

              DH worm gear ratio [40] ? 60

              Maximum number of divisions needed [50] ?

              Hole plates required for all divisions up to 50
              5,8,9,11,13,17,19,23,29,31,37,41,43,47,49,

              Regards, Marv

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

              Location: LA, CA, USA

              Comment


              • #8
                Bruno -- Thank you!

                That looks like the set of plates for George H. Thomas' "versatile Dividing Head", is that true? I am trying to make the same thing, but I don't have any of his castings or materials -- I do have two gears with 60 teeth each.


                Yes, these are the dividing discs for the device from G.H.Thomas. But to produce these dividing discs you need not only the first stage of the device, but also the second stage with the measuring drum and the additional dividing possibility. Then it is possible to make all divisions with the hole disc of 60.




                Bruno, you may want to slow right down for your countersinking... and or may need a fresh countersink... of course what you have will work as is.

                Yes, the 90 degree countersink was not optimal.
                Maybe also the speed and the feed rate was too high. Or all factors came together.
                All this does not look very professional, but it does not harm the use of the machine.
                Many greetings from the southwest of Germany.
                Bruno
                http://www.mueller-bruno.de

                Comment


                • #9
                  Originally posted by Bruno Mueller View Post
                  Bruno -- Thank you!

                  That looks like the set of plates for George H. Thomas' "versatile Dividing Head", is that true? I am trying to make the same thing, but I don't have any of his castings or materials -- I do have two gears with 60 teeth each.


                  Yes, these are the dividing discs for the device from G.H.Thomas. But to produce these dividing discs you need not only the first stage of the device, but also the second stage with the measuring drum and the additional dividing possibility. Then it is possible to make all divisions with the hole disc of 60.
                  Yes, that is exactly what I am planning. I do not have the kit or the castings, but I do have two gears and a spindle -- my lathe can cut the worms. His book is excellent, I'm reading it for the third time this year.
                  25 miles north of Buffalo NY, USA

                  Comment


                  • #10
                    Much success in the implementation of this beautiful project. We hope that we will receive a message from you about the creation of the parts.
                    Many greetings from the southwest of Germany.
                    Bruno
                    http://www.mueller-bruno.de

                    Comment


                    • #11
                      The idea of using hole circle plates with an indexing or dividing head or RT is to provide the needed prime numbers for each additional number of divisions that you want/need.

                      Dividing a circle into equal parts is all about PRIME numbers. It is simply not possible to get an accurate division if ALL the primes are not present somewhere in the mechanism (but yes, there can be approximations). Any worm gear or other gearing that is used will only have a few number of prime numbers in it's basis and then those primes and the combinations, by multiplication, are the only equal divisions that are possible with that basic gearing. So a 40:1 head will have primes of: 2, 2, 2, and 5. That is the complete list of prime numbers that reside in a 40:1 worm gear. And they will allow only 2, 4, 5, 8, 10, 20, and 40 divisions. For all other divisions you will need a plate with a hole circle that contains whatever other primes that are needed. For instance, if you want 3 divisions you will need a hole circle with 3 or a multiple of 3 holes: 3, 6, 9, 12, etc. Often more than one prime number will be included in one hole circle so you may find that 3 in a circle with 3 x n holes, perhaps 3 x 7 = 21. You may also need more of the primes in the worm so 16 divisions would require an extra factor of 2 (2 x 2 x 2 x 2 = 16). There are only three 2s in the 40:1 worm so the fourth 2 must come from any hole circle that has a factor of 2 (any even numbered circle). 32 divisions would require two extra 2s and 64 would need three extras.

                      So the "standard" plates are created by first making a list of the primes that are needed for the divisions you will want and then finding the most optimal combinations of them for making the circles.

                      As a side note, some larger numbers of divisions are prime numbers themselves and the only way to get them is with a hole circle that contains that number of holes. A common prime that is needed is 127 which is used to make the exact ratio gears needed for cutting metric gears with an English lead screw. (127 / 50 = 2.54 and 2.54 cm is the EXACT conversion from metric to the English inch.)

                      The common sets of plates usually provide all divisions up to some number, like 50. As you can see in the above lists 49 is the largest prime that is usually included. 51 is also prime but not included so the complete list ends at 50.

                      If you need to make accurate circle plates, I have explained a no math and no CNC way of doing this to the same accuracy as your dividing head's or RT's worm several times in this board. You can search for that explanation.
                      Paul A.
                      SE Texas

                      And if you look REAL close at an analog signal,
                      You will find that it has discrete steps.

                      Comment


                      • #12
                        Originally posted by Paul Alciatore View Post
                        If you need to make accurate circle plates, I have explained a no math and no CNC way of doing this to the same accuracy as your dividing head's or RT's worm several times in this board. You can search for that explanation.
                        GHT explains something similar in his book, although I have not worked the tables yet. His setup can use the second gear train in either direction, giving a multiplying effect, or a differential indexing effect.

                        He has a neat setup where you have one 60:1 wormgear setup with a 60-hole plate (3600 divisions, or one-tenth degree) turning another 60:1 wormgear setup, multiplying the original 3600 X 3600. Essentially giving one-hundredth of a degree resolution. The amount of movement gets lost in the noise floor of normal shop tolerances.

                        All this with two, 60-tooth change gears (which I have). I can cut the worm as an 6 TPI Acme screw and it will mesh with all of my change gears including the 127 tooth. But the math on that would give me pause.
                        25 miles north of Buffalo NY, USA

                        Comment


                        • #13
                          Originally posted by nickel-city-fab View Post

                          GHT explains something similar in his book, although I have not worked the tables yet. His setup can use the second gear train in either direction, giving a multiplying effect, or a differential indexing effect.

                          He has a neat setup where you have one 60:1 wormgear setup with a 60-hole plate (3600 divisions, or one-tenth degree) turning another 60:1 wormgear setup, multiplying the original 3600 X 3600. Essentially giving one-hundredth of a degree resolution. The amount of movement gets lost in the noise floor of normal shop tolerances.

                          ................................
                          The accuracy that GHT has achieved with its versatile dividing head is 1/1000 degree due to the double 60 tooth pitch and the additional measuring drum with 100 graduation lines.
                          This precision is more than enough for the production of the most different dividing plates.
                          In his book he also describes exactly how this can be achieved. If the graduations do not add up to a full 360 degrees, the missing 1/1000 degrees must be distributed throughout the entire graduation process. This means that the error is only less than 1/1000 of a degree.

                          I have made my dividing discs in this way.
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                          Last edited by Bruno Mueller; 09-11-2020, 05:01 AM. Reason: Supplement with images
                          Many greetings from the southwest of Germany.
                          Bruno
                          http://www.mueller-bruno.de

                          Comment


                          • #14
                            That sounds like a method that could work, but it is not what I have suggested.

                            My suggested method relies on the fact that any worm gear will act as an accuracy amplifier when making a duplicate of an existing hole circle. The amplifier factor is equal to the ratio of the worm. A 40:1 worm will amplify the accuracy by a factor of 40; a 90:1 worm will increase the accuracy by a factor of 90, etc.

                            So if you layout a 127 hole circle with even the crudest methods, you will probably have your hole angles withing +/- 1 degree. If you then use that hole circle to make a second 127 hole circle then, with a 40:1 worm your errors will be only 1/40 of that or about 1.5 arc minutes. Then if you use that second generation circle to make a third one, your error will again be decreased to 1/40 of that or about +/- 2.25 arc seconds. Of course, you need to add the errors in your worm to that number. Very few dividing heads or rotary tables have an spec that is better than +/- 10 arc seconds so that third generation hole circle is down to the same accuracy as your dividing device that was used to make it and no further generations would give you any additional improvement.

                            The beauty of this method is that it uses very little or even no math. There are no tables. The original hole circle can be done using any APPROXIMATE method, including trial and error, that you wish and the third generation circle will be as accurate as possible in your shop. The accuracy is built into the method and is automatic.

                            I have to suspect that in days of old, many hole circles and worms were generated in this manner by the makers of dividing devices.
                            Make the best worm you can with N teeth.
                            Use it to make the best hole circle you can with N holes.
                            Use that hole circle to make another best worm with N teeth.
                            Use that second generation worm to make another hole circle with N teeth.
                            At the third or fourth generation of worm and hole circle with N teeth and holes, they will be down to the basic accuracy of your machines and no further improvement will be possible without building new, more accurate machines.

                            ALL of this is possible in the home shop. With little or no math.

                            Another advantage of it is that any shop with a dividing device can relatively quickly generate a hole circle with ANY count of holes and it will be just as accurate as the OEM ones that were provided with their dividing device.

                            PS: A thought that just occurred to me is that the first generation, approximate hole circle could be made with holes punched in a thin plastic or even a cardboard disk. It does not need to be all that accurate or even very durable. It will be used only ONE time. Even the second generation circle will only be used one time so it could be made from thinner sheet metal, aluminum or steel; 1/8" would be thick enough. Just back it up while drilling it's holes. Only the third generation hole circle needs to be made to standards needed for repeated use in the shop (3/16" to 3/8" thick steel).



                            Originally posted by nickel-city-fab View Post

                            GHT explains something similar in his book, although I have not worked the tables yet. His setup can use the second gear train in either direction, giving a multiplying effect, or a differential indexing effect.

                            He has a neat setup where you have one 60:1 wormgear setup with a 60-hole plate (3600 divisions, or one-tenth degree) turning another 60:1 wormgear setup, multiplying the original 3600 X 3600. Essentially giving one-hundredth of a degree resolution. The amount of movement gets lost in the noise floor of normal shop tolerances.

                            All this with two, 60-tooth change gears (which I have). I can cut the worm as an 6 TPI Acme screw and it will mesh with all of my change gears including the 127 tooth. But the math on that would give me pause.
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

                            Comment


                            • #15
                              Originally posted by Paul Alciatore View Post
                              That sounds like a method that could work, but it is not what I have suggested.

                              My suggested method relies on the fact that any worm gear will act as an accuracy amplifier when making a duplicate of an existing hole circle. The amplifier factor is equal to the ratio of the worm. A 40:1 worm will amplify the accuracy by a factor of 40; a 90:1 worm will increase the accuracy by a factor of 90, etc.

                              Actually, that is exactly what he walks you through in his book. You use ordinary methods to lay out a 60-hole first generation plate, and use that to make a second and third. You use the third generation plate with the compound gear train to make all the others. (Don't take my word as authoritative, I'm still reading the book -- Bruno Mueller has already built it) In each case you multiply the accuracy by 60x
                              25 miles north of Buffalo NY, USA

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