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  • Gulledge Dividing Head Question

    I've been looking for a dividing head, and ran across & picked up this one at an estate sale. One plate, two sided, 15, 16, 17, 18, 19, 20 and 21, 23, 27, 29, 31, 33. Like most used dividing heads I see for sale, it has one plate. I am a novice with these things. What are my chances of stumbling across plates? Can I make one? Can I adapt one from another dividing head? Am I better off buying one of those ChiCom Brown & Sharp copies? I'm slowly tooling up and am a novice on a lot of things.



  • #2
    I acquired a used one with a single plate also. I was able to find a pair of plates on eBay that were the same diameter but turned out to be too thick. I faced them to the correct thickness on my lathe and then cleaned them up on a surface grinder. I guess because of all the holes they made quite the musical sound during facing.
    I see you even got the tailstock so nice find. Even though I now have all the plates I have never used them once and have used it more as a rotab.
    Tom - Spotsylvania, VA

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    • #3
      You will find that the 18 hole circle is the one you will use the most. If you know trigonometry you can make any hole circle you like by starting with a blank plate and moving X and Y (from center) to the coordinates of each hole. Not hard to do if you have a basic calculator with trig functions. If you don't know trig find someone who does to guide you through it - try a high school kid. It is a bit tedious but it can be done. I made a 25 hole circle once many years ago - I don't remember why - and it worked fine.
      Last edited by DATo; 12-07-2019, 07:43 AM.

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      • #4
        Perhaps one of the first things to verify is the ratio of the dividing head. Forty to one is common, but there are others. That's critical to knowing which number sets on the plate you need for any particular division. For instance, I have a horiz/vert rotary table that's 72:1, and a dividing head looking more like yours that is 40:1 It works out that some particular divisions are easier on one or the other.
        .
        "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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        • #5
          Originally posted by DATo View Post
          You will find that the 18 hole circle is the one you will use the most. If you know trigonometry you can make any hole circle you like by starting with a blank plate and moving X and Y (from center) to the coordinates of each hole. Not hard to do if you have a basic calculator with trig functions. If you don't know trig find someone who does to guide you through it - try a high school kid. It is a bit tedious but it can be done. I made a 25 hole circle once many years ago - I don't remember why - and it worked fine.
          The BOLTCIRC program on my page will generate the x,y coordinates for any hole plate. Here's an example output...

          Boltcircle specification:
          Radius of bolt circle = 10.0000
          Bolt hole diameter = 0.5000
          Spacing between hole edges = 11.2557
          Angular offset of first hole = 0.0000 deg
          X offset of bolt circle center = 0.0000
          Y offset of bolt circle center = 0.0000

          HOLE ANGLE X-COORD Y-COORD

          1 0.0000 10.0000 0.0000
          2 72.0000 3.0902 9.5106
          3 144.0000 -8.0902 5.8779
          4 216.0000 -8.0902 -5.8779
          5 288.0000 3.0902 -9.5106


          Which holes you need (a function of the dividing head's gear ratio) can be found using my DPLATES program. Another example output...


          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,


          DPLATES is included in the DIVHEAD archive on my page. BOLTCIRC is also on my page. Both programs are free.



          Regards, Marv

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

          Location: LA, CA, USA

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          • #6
            Just find a program on the 'net that will print a circle of marks or use a CAD programme. Then use that stuck on cardboard or even a 3D printed version to make a real metal plate. No need to get too hung up about the first one being just paper as the reproduction process improves the accuracy by the ratio of the head - normally 40. For amateur use you can use Aluminium for the plate.

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            • #7
              Thank you all for the info.

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              • #8
                Actually, while it seems surprising, the accuracy of the holes may not be that critical (notice I did not use the word "important").

                Any positional errors in the location of holes in the plate will be divided down by the 40:1 or whatever the ratio is. If you can get the holes within 40 thou, then the result will be within 1 thou in the part you are making, for features (gear teeth, etc) that are at the same diameter as the plate holes.

                And you ought to be able to get the dividing plate holes to more like a 10 thou max error if you halfway try. That would make the accuracy more like 2.5 tenths at the same diameter as the plate holes.

                Should be "good enough for the home shop"......... although I will clearly not criticize anyone who wants the plates accurate to better than 10 thou.
                1601

                Keep eye on ball.
                Hashim Khan

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                • #9
                  Sure looks like an Ellis Dividing head.
                  Was Gulledge a forerunner of Ellis ?
                  Rich

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                  • #10
                    Understand from a PM posting in 2007 that a Gulledge has a #5 B & S Taper but the second link says #9 B&S ??

                    https://www.practicalmachinist.com/v...g-head-129620/

                    Nice rebuild article


                    https://www.hobby-machinist.com/thre...8/#post-421316

                    Rich
                    Last edited by Rich Carlstedt; 12-08-2019, 01:21 AM.

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                    • #11
                      Can you make your own plates? Yes you can. Others have said so above and I have been explaining the process for years.

                      Yes, the dividing head or rotary table will act as an accuracy amplifier when you make a plate from one that is only approximately laid out. I have done the math and, with the common ratios used in the worm gears in these devices, you can start with a plate that has really bad errors and by the time you make a third generation copy, it WILL be just as accurate as your dividing head or RT. If you will only use the final plate with the dividing head or RT and not for direct dividing, then the second generation copy will be good enough because you will get a final boost in accuracy when it is used on that device.

                      So you can use Marv's programs or do your own X-Y formula or just do a crude job of laying out a circle by hand and use it to make a second generation plate. And that, second generation plate, when used on the dividing head or RT will give you all the accuracy that the device is capable of.
                      Paul A.
                      SE Texas

                      Make it fit.
                      You can't win and there is a penalty for trying!

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                      • #12
                        Just so you know a mill with a good dro can drill up to 99 holes quite quickly, with great accuracy, as should most CnC machines.

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                        • #13
                          You guys definitely pointed my research in the right direction. I'm still cleaning up the mill I bought, and a second smaller lathe. Usually work slows down for me this time of year, but it has picked up instead, so I'm finding time where I can. I have one running lathe that I've used a lot more than I thought I would. I'm always repairing something. I have no idea why it took me so long to acquire a lathe. I've been hitting every sale I can in my free time to find bits and pieces, cutting tools, etc. I'm getting there, slowly but surely.

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                          • #14
                            Not really related, but...
                            The Gulledge dividing heads are kinda rare.
                            I have a Gulledge rotary table, it is 7-1/2" diameter.
                            I use it on my Clausing 8520 mill, and I understand
                            they were a factory accessory for this mill.
                            A great size accessory for the home shop guy.

                            --Doozer
                            DZER

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                            • #15
                              mrPete222 is making dividing head plates right now.
                              https://www.youtube.com/watch?v=OjdJtnFgZF4

                              David Merrill

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