Small Hole Drilling

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  • John R
    Senior Member
    • Mar 2006
    • 223

    Small Hole Drilling

    I need to drill #60 thru the 0.094 dia. stainless steel stem of the intake and exhaust valves for a model engine. My HSS #60 went dull about 25% thru the first one. Should I use a solid carbid drill or maybe a straight flute drill or what ever else? Any advice will be appreciated
    Thanks,
    John R
  • Carld
    Senior Member
    • Aug 2006
    • 6061

    #2
    Carbide may be the better choice but what rpm are you drilling at?
    It's only ink and paper

    Comment

    • Toolguy
      Senior Member
      • Jan 2010
      • 6666

      #3
      Drilling SS

      Run the drill about 200 RPM or less. Too much spindle speed creates too much heat at the cutting edge, making the stainless harder and the drill dull. Use cutting oil too. On the first one you may need a carbide drill now, try a different one with a new or sharp HSS drill and see how it goes. Carbide spade drills are the toughest, especially in the smaller sizes. They are fairly cheap too.
      Kansas City area

      Comment

      • John R
        Senior Member
        • Mar 2006
        • 223

        #4
        Speed was 850 RPM. 1700 and 2400 are available
        John R

        Comment

        • bob_s
          Senior Member
          • Apr 2005
          • 1344

          #5
          Use an evaporative coolant, like iso-propyl alcohol, with steady feed - this is not the place for peck drilling

          Comment

          • John R
            Senior Member
            • Mar 2006
            • 223

            #6
            Thanks for your help
            John R

            Comment

            • Ron of Va
              Senior Member
              • Apr 2009
              • 359

              #7
              I have found that a 135Ø› point works much better on stainless, than a 118 degree point. So when you resharpen that bit, keep that in mind.

              Comment

              • Black_Moons
                Senior Member
                • Aug 2009
                • 9096

                #8
                How does one resharpen a #60?
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                Comment

                • Walter
                  Senior Member
                  • Feb 2006
                  • 428

                  #9
                  Carefully

                  Heh, sorry. couldn't resist.

                  Comment

                  • macona
                    Senior Member
                    • Aug 2006
                    • 9425

                    #10
                    1900RPM minimum, thats at 20SFM which is at the bottom of the stainless recommended SFM range.

                    I dont know how deep you are drilling but if you are going more than about 1/8" deep look at a parabolic drill from Ghuring. They recommend cobalt for stainless, and since you may have hardened the hole already it might be worth getting.

                    Comment

                    • rklopp
                      Senior Member
                      • Feb 2003
                      • 580

                      #11
                      Do you have a way to drill with automatic feed? You're much likelier to succeed if you do. Set the combined chip load per revolution at 1% of the drill's diameter. The feed rate is then the chip load per revolution times the RPM. A #60 at 850 RPM should therefore be fed at 0.34 in/min (0.04 in/100 *850). You could go up to at least 5,000 RPM at 2 in/min feed. this would give you 52 ft/min nominal cutting speed. Just plunge right in. Do not pause or back off for any reason. Also, use a screw machine length drill to increase the stiffness.

                      Comment

                      • Mcgyver
                        Senior Member
                        • Mar 2005
                        • 13403

                        #12
                        I'm not the most experienced machinist of stainless around these parts, but if you didn't use a free cutting stainless you maybe be scuppered. With ss, unless free machining, the only hope machining it is with each successive pass being deeper than the miserable work hardened layer left from the previous one---in other words each time the bit comes around you need to be advancing it several thou...not easily done with such a small twist drill
                        located in Toronto Ontario

                        Comment

                        • John R
                          Senior Member
                          • Mar 2006
                          • 223

                          #13
                          I got it done with a short drill that had a fat shank. Of course it broke when it came through but did not clog the hole. I also tried a single flut drill but it did not work.
                          Thanks for your help,
                          John R

                          Comment

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