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Fixture ideas...

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  • Fixture ideas...

    I need to support the gear ring in this picture 2-1/2" above the rotab for gear cutting.

    It needs to be secure as these are 4dp teeth cuth full depth in one pass. The cut is applied by raising the table.

    Material is cast iron.

    Any suggestions?
    If it does'nt fit, hit it.

  • #2
    Four 1X2X3 blocks with appropriate T-bolts?



    • #3
      Four blocks 2 1/2" thick/tall between the RT and the ring. Hold down clamps W studs etc in the RT T slots to hold the ring in place with the clamps on the inside of the ring.

      I'd probably go with aluminum for the blocks so you could cut into them if necessary with the gear tooth cutter. Keep in mind they could be square, rectangular, or cylindrical or even a mix of them just as long as the 2 1/2" dimension was the same on all 4 spacers.

      Indicate the ring true with the RT, center up the cutter and go to town.

      This of course assumes you're only making one ring gear. If you're making multiples, make a fixture that bolts to the RT and has a centering pin. The fixture would also locate the ring using the ID and one would use clamps on the inside of the ring to hold it in place.

      Please show us what you finally come up with.


      • #4
        Thanks, I was leaning towards four blocks or columns with central bolts so the blocks are fixed o the rotab and then standard clamps and jacks pulling the ring down onto the columns.

        This would seem to offer some extra stability I think.

        I have two rings to do and normally use the hub to mount but on this engine the hub is bigger than the rings.

        I guess I should mount a DTI opposite the cut to watch or shifting as well.

        With four points of support would the unsupported sections be in for a rough ride?
        Maybe I should fit four unclamped columns between?

        Will post a picture when done
        If it does'nt fit, hit it.


        • #5
          you could aid the ridgidity, by putting the 4 riser blocks at the points where the inner bolt circle is left in free space,

          before you rig it all up get some bolts that will go through the bolt circle, grind the heads smooth and place the head against the rotary table with a nut on the thread and then the ring over the top,set up the riser blocks and fully clamp, then use the jacking bolts in the same way as machinist jacks to support the ring further, ideally clamp over the top, but this might not be practical

          if your cutting force is downwards, this will help take the spring out.



          • #6
            Unless it's supported all the way around I'm thinking the casting is going to crack. Turn a plug with enough meat so that it can accomodate heavy clamps.


            • #7
              There is a place in CA that sells the drops from making some sort of big bearings. A stack of those would suport that ring better than blocks. Frank Ford posted a reference to the site a long time back. I am on the road right now and don't recall the name.
              Byron Boucher
              Burnet, TX


              • #8
                Are you cutting the teeth into that stepped face or on the OD?


                • #9
                  If your doing 2 why not bolt them back to back & cut both at the same time?
                  "Let me recommend the best medicine in the
                  world: a long journey, at a mild season, through a pleasant
                  country, in easy stages."
                  ~ James Madison


                  • #10
                    Cut a steel disc which fits inside the stepped section use the existing bolt pattern to bolt the blank and the disc together and drill a central hole to mount it on the rotab..
                    As others have said the cast iron doesnt like a rough ride.


                    • #11
                      IF its the "edge" you want the teeth on and IF I am understanding rustybolt correctly, I think that is the way to go.

                      I'd flip it over from the photo so that lip can act as location and support and make a "plate" large enough and tall enough (of the right configuration) so as to allow for some through holes that you could bolt directly to some "Tee" nuts in the T slots of the "face plate".

                      IF it is the inside edge where you want the teeth, I think it would be more or less the same just with a hole in the middle that would allow the cutter clearance.

                      To me it is sort of like the features similar to a plain back lathe adapter plate but with teeth...if that makes any sense.


                      • #12
                        I'd use a heavy wall/sched 80 section of pipe to support the part. Studs and straps clamps to hold it down.


                        • #13
                          A note to not overlook wood as an economical fixturing material to use in conjunction with more localized, metal height spacers. A piece of Al. large enough to make a fully supported fixture as some advise would cost a large chunk of change. A milled hardwood (heck - even something very inexpensive and common) locating fixture to provide full support underneath with carefully fitted and faced metal rods could be made very affordably. Think of rebar in concrete for a (poor) analogy.


                          • #14
                            Yes, the teeth are in the OD, at the face the cast is 3/4" thick and the ring is 8" dia.

                            I have nothing that could make a solid riser 2-1/2" tall and although i have two to do, the next one is 10" dia. so a new fixture will be needed.

                            The nect ring bolts to the side of this one so there is a possibility of sharing a mounting method.

                            the threads in the bolt circle are only M5 so not very meaty but could take shouldered bolts etc i guess.

                            Wood as a fixture, at least any wood that i could get would be a bit springy i would think?

                            If it were a production job, i would have no hesitation in making a solid fixture, registered to the central rotab hole, bolted down and the ring clamps direct, but for a one-off, needs to be as simple as possible.

                            I will have a play around tonight.
                            If it does'nt fit, hit it.


                            • #15
                              What species of wood wouldn't crust under the clamping preasure?

                              Try a scrapyard for short sections of heavy wall pipe. I have a pile of rings in various diameters and heights that I've sawed from pipe for use in similar machining operations. All have been obtained as scrap, some from the yard, others from a municipal sewer line install, large nat. gas pipeline construction, etc.