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Pre drilling for boring on mill

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  • Pre drilling for boring on mill

    Had a brilliant brain wave today, at least I think so {g}
    Like most people when boring on the mill I drill out to the largest size I can then bore to the final size.
    Most times the drilled hole isn't critical, it's just a method of removing material as quickly as possible.
    The largest size is usually limited by the size of the collet or taper of the machine.
    On R8 machines this is usually limited to the largest No 2 morse drill with adaptor or the use of a stepped drill.
    Hence my brain wave. Whilst looking round for a drill the other day for a job I came across this stubby 1 3/4" drill on a No 4 morse shank. A quick measure up and I could see the possibilities. Twenty minutes machining time got me this:-

    A genuine Stevo R8 drill [ patent pending ]
    Thought I'd share it.

    John S.

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

  • #2
    We use a spade drill. It works great. We have blades that go up to 3.5"


    • #3
      I could of used it today.Had a forklift front end part on the mill,drilled to 1" bored to 2"
      Put the picture in my "to make" file
      please visit my webpage:


      • #4
        Whoa, that's a monster drill John, but who's the poor bugger that's been squashed under the platform that it's sitting on? (check the lower right corner of the pic)... not a total loss though, the wrist watch might be ok couldn't resist...


        • #5
          Is that a high speed drill?
          what did you machine it with?
          How did you chuck it?

          Looks nice!
          Good idea, less overhang.


          • #6

            Did you set your digital camera to a retro mode. It looks like a scence of a bad B movie from the 70's. LOL



            • #7
              Office space is also at a premium.Just had to find a handy 'shelf'
              The easiest was on top of a pile of mags.

              Drill shanks are quite easy to turn with an insert tool. The drill doesn't start getting hard until the base. The centre hole taps OK with normal HSS taps

              Retro mode ? Everything I have is retro mode.
              All the good stuff came from years ago. Perhaps I should rephrase that. "All the affordable stuff comes from years ago " {g}
              Actually the shot does look retroified. I had a load of manila envolopes on the desk ready for mailing tomorrow and it obvious cast a shadow over the shot.

              John S.

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


              • #8
                Excellent idea. I have thought seriously about butchering a fixed shank boring head to suit the lathe tailstock along with some nifty R-8 shank stuff that just will not fit my MT#2!

                I think I will stay away from the NST-50 stuff...for now.


                • #9
                  How did you chuck it? Also how did you machine the taper?


                  • #10
                    Hold the drill body in a four jaw chuck with copper blocks between the jaws and drill. Indicate at the large end of the taper, fo to small end indicate. Tap till straight. Repeat if required till running true. Dress up center if nicked up. Place live center in tailstock. Have at it. To cut the Taper set up the taper attachment if you've got one before you even start otherwise set compound at appropiate angle making sure the tool is on the center height.

                    Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.