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Fly Cutter Sharpening and use

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  • Fly Cutter Sharpening and use

    As a newbe to the milling arena I have read that using a fly cutter is an efficient and easy way to face and surface material. I purchased a set of these little guys with some tooling. I have limited experience sharpening High speed steel for my lathe, but this seems to require a different geometry. Is there any online referance for sharpening these tools?


  • #2
    Originally posted by skipd1
    I have limited experience sharpening High speed steel for my lathe, but this seems to require a different geometry. Is there any online referance for sharpening these tools?
    a newb maybe, but you're showing lots of machinist acumen picking that up.....not a lot seem to...most just slap in a knife tool. It'll make chips, but would be the equivalent of facing with it in the lathe - it'll make chips but far from idea.

    What is ideal imo is a facing tool - the kind you grind with a chip breaker. You just have think through exactly where is the cutting edge, the rake the clearance. I'll try and find a pic I have on photobucket somewhere

    here found it... a thread with lots of i recomend is a lathe facing like in post 8. Unless you're plunging the fly cutter, you are cutting on the end of the bit not the side......assuming the cutter is this style not the hold-the-bit-straight-up-and-down style
    Last edited by Mcgyver; 04-11-2012, 06:20 PM.


    • #3
      It's a bit more than difficult to describe the geometery of a fly cutter
      bit but a good way to start thinking about it is "it's SORT of" like a
      lathe bit for turning towards the tailstock. Of course the clearance at
      the "front" has to be suitable for the radius of the swing. I think there
      have been some pictures posted of typical cutters here or on other


      • #4

        David Merrill


        • #5
          Try these cutter profiles. The 45 degree leading edge angle works best.

          It's only ink and paper


          • #6
            I was in the same fix awhile back, and stumbled on to that drawing shown on the "madmodder" link; I ground the tool in my hamfisted, eyeballing fashion, and had a chance to try it out last week on a chunk of aluminum, & here is a pic of the result: no great shakes for a real machinist, but for someone with no knowledge of proper speeds or feeds, I'm pleased with my first attempt. The machine used was an Emco Maier Super 11 with the Milling head.

            Eventually I want to make an V block optical center punch, like I saw in an issue of HSM.

            My, point is, don't be afraid to grind a tool yourself.


            • #7
              Originally posted by demerrill

              that's a good link David; I can see how John's grind follows along the lines of a broad radius nose on a lathe tool for finishing. I concede that would be a superior tool for finish - I think you'd want a faster feed and small DOC with it and revert to facing tool style I suggested for more aggressive material removal.

              I look forward to giving it a try.


              • #8
                Fly Cutter Sharpening and Use

                Thanks everyone. This forum is the greatest!! Lots of great info to start me into the fly cutter foray!
                Thanks again for all the imput and photos



                • #9
                  Initial fly Cutter use

                  I finally got around to acquiring and assimulating all the great info from my last post about sharpening fly cutters. I hand sharpened and installed the 1/4" HSS tool in a 1 1/2" fly cutter with a MT2 arbor in my Clausing 8520. I set up a 3"x 4"x 3/4" mild steel block in my vise and started to face off the block with .008-.010 cut and very slow hand feed. Set the rpm to about 600rpm. I was quite suprised at the quality of the finish and didn't seem to notice any difference using cutting fluid or dry. The 8520 seemed to chew smoothly through the surface with ease. My question is can I go higher in rpm with this tool as it is sweeping the entire width of the block in a single pass, and with smaller fly cutters do I need to up the rpm??



                  • #10
                    I made this up a while back to help me with large diameter stuff. In your case the swing of the flycutter is the diameter. 80 SFM is for steel and 200 for Aluminum. In both cases using a HSS bit.

                    SURFACE FEET PER MINUTE
                    RPM = SFM x 12
                    Pi x D”

                    Steel: 80 SFM. Aluminum 200 SFM


                    P.S. I can't seem to format the layout. The Pi x D" should be under the SFM x 12.
                    Last edited by ammcoman2; 05-24-2012, 08:05 PM.