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  1. #21
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    Quote Originally Posted by EPAIII View Post
    It is not a tilted cone, it is a combination of a cone and a helix/spiral. As you rotate past the cutting edge, the angle of the cone, as measured to the axis, constantly decreases. This creates the clearance. So you can not generate this shape by tilting any cone with a constant angle. The action used to create this is much the same as that used to create "conical" tips on drill bits. The angle must change while the tool is rotated across it's face.
    This could be checked by chucking a single tooth CS in yor lathe and placing an edge of a cutter in the compound parallel to the cutting edge of the CS. Then rotate the chucked CS say 180 degrees and crank the cutter in until it is against the side of the cone. Does the angle change or does the cutter remain in full contact with the side of the cone? If cutter is swung and spiraled in the angle will change. If it advances spirally as driven by a fixed lead screw it will remain parallel.

    Denis

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    Quote Originally Posted by EPAIII View Post
    We never did get an answer to the type of countersink question. Different types need different techniques. !
    I was trying to grind 3-fluted csinks.

  3. #23
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    I was trying to grind 3-fluted csinks.
    That should work. It doesn't matter how you tried it with what work head. But really, it should work.

    Was the drill running in reverse?


    Nick

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    '3-flutes' usually offer plenty of room to get a wheel into the flute. Helps if you have a cg, tho'. I'd face the flutes as long as you can maintain a reasonable primary land width at the cutting diameter. After that, top-grind but keep relief angle low and let 'em feed slow into the cut with that in mind.

  5. #25
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    It does sound like some mentioned earlier, the flute was not timed correctly with the cam.
    Poly choke as well as R & A machine indexer shown previously will do that work fine on multi-flute tools....Just so long as first flute is placed correctly.

    smt

  6. #26
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    You need a machine like a RO grinder, aka Royal Oaks, now owned by Seneca Falls Technology. These are cam operated grinders, been around since the 50's or 60's

    Royal Oak® Grinders

    I have one of the machines that I am rebuilding. They have a very detailed manual that is used with their machines but I would assume would also work with other cam operated grinders as to how to set up for various tools.

    Tom

  7. #27
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    Quote Originally Posted by dgfoster View Post
    I did exactly that. I used a 20 TPI screw to get the desired relief. Worked out well. Quite a bit of work, but an interestinbg design project. You do not need the boss with the ten holes on the top of the spindle housing for this application so I sawed it off and cleaned it up with a file. Sometimes that boss gets in the way otherwise. Various "lead screws" can be used for varying relief. Has other applications as well if no lead screw is used and is a simple spinner.

    I will likely power mine similar to the compound powerfeed for spinning various cylindrical items not using the lead screw.

    Denis
    I was on vacation for 3 weeks and just got back. I wanted to post pics while I was gone but did not have them with me.
    Here are some pictures of a solution using a simple spindex modified to sharpen single-flute countersinks. It will have additional
    add-ons and applications as time goes along. I believe the patent posted previously by Heavy Metal in this thread may be a simpler and better solution for the sole purpose of single-flute countersink sharpening.

    "Heavey Metal
    Attached Thumbnails Attached Thumbnails single-flute1.jpg   single-flute4.jpg   single-flute5.jpg   single-flute3.jpg  

  8. #28
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    Default I wanted to add some suggestions to an old post

    For anyone using the Chinese UD3 style or Shars style 5c U3 collet grinders I have found if you start at your cutting edge and roll the chamfer (presuming single flute) while you slowly pull the chamfer into the grinding wheel it will sharpen it sufficiently to use and get clean chamfers. Similar to a a cam effect by rolling and pulling. I have taken chamfers that were incorrectly sharpened and/or damaged and been able to put a new edge on them saving $40-$50 chamfers. A box of 30 or so chamfers probably paid for the machine sharpening them all to a razor edge. Despite the budget friendly grinders they work well for something that is infrequently used. I would imagine a similar technique can be used on other grinder machines. I set the collet at 45 set for the 90 chamfers and approx 10deg pitch for cutting aluminum. Best thing to do is just play with it using a cheap chamfer until you get it. The other comments here are correct if you don’t have a back relief it will just spin and not cut anything like a tapered dowel. Relieving the back edge just enough to get a smooth finish. I found if your chamfer leaves more of a chattered finish that the relief is probably slightly excessive and it’s grabbing into the material too aggressively. So back it off if you see that square like chattered finish in your taper. If you notice it goes away when more pressure is applied it likely confirms too much relief. This is our experience and perhaps others have had similar or differing experiences though it works for us here.


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