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Broken Drill

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  • Broken Drill


    I have a bronze cannon cast around a 2" OD 304 SS tube - 1/4" wall - bore = 1 1/2"

    I was trying to insert the standard cannon wick (fire for the first time for July 4th) and the hole was too small.

    I used a hand drill and an 1/8" drill bit and plenty of cutting fluid but the drill broke in the hole.

    The drill part left in the hole is approximately 1 - 1 1/2 deep and about the same size.

    The final hole can be as much as 1/4" or even a little larger.

    Any ideas on how to extract this broken drill?


    PS: I've been registered for about 5 months and have been learning so much reading the board. Unfortunately, each time I tried to throw in my two cents, my password did not work. For this new topic I re-registered again.

    PSS: My first question had to do with a power hacksaw and castings. Someone refered me to a Popular Mechanics article. I completed the power hacksaw - nothing like the article and it works great. Now that "I'm back" I'll post some pictures.

    Thanks again for all the good information.

  • #2
    Make a powder charge wrapped in paper such as used in a fireworks mortar. Run a length of fuse from the charge long enough to reach out of the barrel. Drill a hole in a shot large enough to pass the fuse through the shot. Load the cannon with this charge and fire it. Bet the drill bit comes out.
    Free software for calculating bolt circles and similar: Click Here


    • #3
      I am guessing that the drill snapped just as it “broke thruâ€‌ into the bore. If so, make a plug that is a slip fit into the bore. You can relieve most of it. Only the end needs to be the slip fit. Now slide this down into the bore. As the plug passes the drill tip, it might push it back out just enough to loosen it. Hopefully then you can grab it or work it out. Force compressed air down the bore. This might blow chips out the drilled hole. The chips are helping to lock in the drill.

      If that doesn’t work, turn the barrel over and drill another “fuseâ€‌ hole in line with the first. Then slip in a punch and drive the drill out. Course, now you have to plug one of the holes. Tap and screw in several set screws. Even if someone sees it on the bottom. A set screw just below the surface will look like it belongs there. I will leave it to someone else to comment on the best thread to offer the most strength against the powder charge. Chief Mcgee


      • #4
        Alum will dissolve a tap broken in aluminum without affecting the aluminum, possibly brass & stainless also will be unaffected.

        Similarly, a mild acid solution, hydrochloric or sulphuric, would also probably dissolve the steel enough to remove the drill before the base material was affected.
        Jim H.


        • #5
          You might check with an engine (auto) rebuilder to see if someone has a metal disintegrator. Go to google type in electroarc to find out the possibilites. If you were in San Diego I could remove the drill for you.
          [email protected]
          Herm Williams


          • #6
            sounds like quite a barrel...some good ideas here, but before doing anything really drastic that might damage it, consider outsourcing to a shop with a sinker edm. at some point, if the simple stuff doesn't work, spending a few $$$ becomes more appeally than damaging it...then again maybe it's too big to lug around - 1.5" bore - how heavy is this thing?

            [This message has been edited by Mcgyver (edited 07-08-2005).]
            in Toronto Ontario - where are you?


            • #7
              OK, this is the long way around, but I went to the cnc workshop that Roland Friestad organized. There was a gentleman there who is publishing a book on building a small "inexpensive" EDM machine. He demo'd it at the show. Seems like the ideal machine to remove your broken drill without destroying your work.


              • #8
                Thanks for all the suggestions. I have a friend who has a friend that runs a machine shop. It looks like his willing to take a look at it. Hopefully, he can handle the removal.

                Thanks again.