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Any reason not to shorten a spindex?

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  • Any reason not to shorten a spindex?

    I am building a universal head for my T&C Grinder using a cheap 5C spindex. On the original machine the spindex portion is quite short and low. The length of the tube on the new spindex prevents the holder from turning completely around. Is there any function of the spindex that would be impeded if I shorten the tube?

    Here are some pics of what I have so far. I still need to do the final polishing of the edges where the graduated markings go and make the marks.





    Here is the original:


  • #2
    I think the only drawback of shortening the tube would be that you would be limiting the capability of grinding longer end mills.
    How about if you flip the two piviot point discs around so they are on the under side, then you would be free to swing the fixture around.

    Also I'm assuming you mount a finger under the end mill somewhere to keep the angle correct.

    JL................

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    • #3
      Actually that isn't a bad idea. I would need to change where the angle graduations would go but that would also solve the height issue.

      Yes, I am trying to figure out how and where to mount the finger next.

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      • #4
        Personally I wouldn't, if you plan to do the flutes and slide the spindex rather tan move the table it's barely long enough as it is, in fact I've extended mine. But I also added air into the spindle bore and a tilting base to make things easier. There are some pics in the post #1789 of the shop made tool thread, but it doesn't have the spindle extension/ handle shown.

        If nothing else You could ditch the handle to stop it fouling the table, and add a large hand grip instead.

        Brian

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        • #5
          Replace the handle with a handwheeel, far more comfortable to use.
          .

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



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          • #6
            Originally posted by goodscrap View Post
            Personally I wouldn't, if you plan to do the flutes and slide the spindex rather tan move the table it's barely long enough as it is, in fact I've extended mine. But I also added air into the spindle bore and a tilting base to make things easier. There are some pics in the post #1789 of the shop made tool thread, but it doesn't have the spindle extension/ handle shown.

            If nothing else You could ditch the handle to stop it fouling the table, and add a large hand grip instead.

            Brian
            If you slide the table to grind the flutes you just won't have that sensitivity in the feel of keeping the end mill on the finger and the result will probably be a poor grind and you would also have to mount the finger on the base of the machine not the table.
            As it stands a spindex doesn't have the same feel as an air spindle, actually they have quite a heavy drag depending on the oil you use.
            Putting air to it is a good idea if it works.
            John is right, remove the handle. I would make a knurled extension tube and fit it to the back of the spindex spindle.

            JL...................

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            • #7
              Originally posted by JoeLee View Post
              If you slide the table to grind the flutes you just won't have that sensitivity in the feel of keeping the end mill on the finger and the result will probably be a poor grind and you would also have to mount the finger on the base of the machine not the table.
              As it stands a spindex doesn't have the same feel as an air spindle, actually they have quite a heavy drag depending on the oil you use.
              Putting air to it is a good idea if it works.
              John is right, remove the handle. I would make a knurled extension tube and fit it to the back of the spindex spindle.

              JL...................
              Excellent points. I really don't like the handle that comes with it and the table moves nicely but it has a fair bit of mass and sometimes you get a little "jump" as it starts moving. (That is more due to reaction time on my part than a failing of the grinder.) Not something you want on a very fine endmill grind.

              I would like to add air to it at some point and reverse the nose as has been documented in other threads.

              When I get brave enough, I will put a small thread on the back end to reverse the index disc.

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              • #8
                another thing is; you want to pull the cutter along the finger rest, from shank to tip, once you get to the end the cutter falls off the finger, and you index round a flute
                to do this on a fixed machine and get the cutter back to the starting point of the grind, you have to either back the table away from the wheel or risk trying to get the cutter to slide along the finger while the helix isn't being held naturally by the force of the wheel, you're pushing the helix up hill in practice.

                if you look at the video on youtube of a weldon air bearing it will make sense, and is why i made a tilting base so you can withdraw the cutter from the wheel index the flute, return to the start all without risking dinging the cutter on the wheel. you can also make the tilt multi-position so you can do primary and secondary relief without removing the cutter or making major changes to the machine set-up.

                i find grinding the flutes easier than the cutter tips with my home brew air bearing , and to add to joelee's point, the air supply improves the smoothness and feel about ten fold.

                here is the handle/ spindle extension i made, note spindex was removed from the tilting base for another job and hasn't made it back together yet.



                Brian

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                • #9
                  Hey Brian, that is interesting how you ported the air in several spots on the spindex housing. Did you do them all at once or add each one until you got the smooth feel that you were looking for???
                  My KO air spindle has three holes spaced 120 deg. apart in the center of the bearing, I've never seen the air ported on the ends of the housing.

                  JL..............

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                  • #10
                    Brian,

                    I see you're using a Clarkson Mk 1 - do you put the tool head on the left side as shown? I believe the fignger would have to be on top and the wheel would try to rotate the endmill away from the finger.

                    The reason I ask is I recently got a Clarkson, and I'm trying to use a Gorton tool head on it. Due to the smaller wheel I have (4"), I have to have the table slide at an angle to the wheel vice perpendicular to provide clearance for the tool head.

                    I could go parallel to the wheel, but then the primary and secondary clearances would have to be ground separately. I use a method published by Hanita where the slide is set about 5 deg from perpendicular. The left edge of the wheel is then closer to the end mill, and forms an elliptical grind as the end mill's helix drops below center. Hard to explain, but if set up right, it works very nice.

                    Wayne

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                    • #11
                      JL I researched a fair bit on air bearings, purely across the net, most had an inner sleeve that distributed the air via three equi spaced holes, but it isn't possible on the spindex, one chap tried something similar to mine, but ported up the base and cut circular grooves, but I could tell that wasn't how an air bearing should be done, idea is that if you load the spindle it restricts the port and the air pressure rises causing it to self centre. Hence i did it my own way

                      I did three ports at each end all 120 degrees. they were back spotfaced to ensure the area acting on the spindle is all the same,





                      the only trial and error part was that the manifold that distributes the air has metering orifices and I restricted the top two ports slightly to account for the weight of spindle, in all honesty though I don't think it matters and if you get air in there it may or may not fully float, but it will for certain reduce the friction massively.


                      Wayne, This is how I position it, the table slide is locked and just the spindex used


                      The Base tilts along with finger to allow indexing to the next flute, and also a multi position stop gives primary and secondary clearance angles.



                      Brian

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                      • #12
                        Nice job and pics as well. I know that my KO air spindle works on very close tolerances, like about .0004.
                        Here is what the bore looks like on my KO. You can see the three holes in the center. There are no orifices or metering jets with this design.
                        recommended air pressure is 50 - 80 PSI. But mine leaks quit a bit of air where you see the red marks. The bore is slightly worn. The leak causes the spindle to stick. I've been thinking about having the bore honed, the spindle centerless ground and chromed and then reground to the proper tolerance to fit the bore. I don't know what else I could do.

                        JL..............................


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