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DIY radius "milling" cutter for use in boring head

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  • DIY radius "milling" cutter for use in boring head

    Okay... Trying another one of those "fake casting" creations. I have a plate with four pockets of 1-1/8" diameter, 5/8" deep. Around the top edge of the pocket bore, I want to put a small radius rather than having a sharp corner. I have a cheap radius milling cutter BUT... My mill is not large enough to accommodate the swing when these holes are centered under the spindle on a rotary table. I thought about it a bit... Next best idea I've had is to center the holes under the milling spindle and use a form tool mounted in the boring head. Problem... no concave radius tool in the shop. No tool grinder, either So I started wondering if I could make one. Items on hand:

    - 1/2" drill rod (torch and oil available to harden)
    - one small ball end mill
    - various small, normal end mills

    Here's the question. Can I...
    - mount the drill rod perpendicular to the milling spindle
    - mill a concave, half-diameter profile on the end
    - turn drill rod 90-deg.
    - mill off half-diameter of the drill rod flat over the length of the profile
    - harden, mount in boring head and cut?

    Wouldn't I need a flute or a clearance edge or... this is where I'm not sure what I'm doing Here's a drawing, but I'm having a hard time wrapping my head around this. I'm not sure this is really what it would look like at all, but at least it illustrates my concept:

  • #2
    Instead of turning the rod 90* for the second cut, turn it 95* to form a cutting edge. Then turn it a second time, to, say 100-110* to form a relief, leaving just a small land of the 95* cutting edge. Then harden and stone the cutting edge. It might work on brass or aluminum but I doubt it would last long on steel. (Angles are guess work, but should give a starting place for discussion.)

    A multi-flute cutter could be made in the same manner, indexing it with a simple collet block. It might hold up a bit better than the single flute cutter.
    Jim H.


    • #3
      Doh! Just use the radius end mill in the boring head aligned as a single-flute tool Should've thought of that waaaay sooner. There I go making it complicated.

      That said, yeah, thank you JCHanum. That made sense. It is for use on cast iron... or at least some sort of iron that cuts real nice that came from the 'random used tooling' department of a used machinery dealer. I think the previous owner was using it as a lapping plate.


      • #4
        That went far more pleasant than I expected w/ the milling cutter in the boring head.