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Broken drill and stud

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  • Broken drill and stud

    I have been given the job of removing a broken cylinder stud from a Honda motorbike upper crankcase casting, the last bloke to have a go at it broke a drill off in it as well!
    I have tried to twist the drill out backwards with no luck so I want to try Nitric Acid, will the Nitric Acid dissolve the broken stud as well as the drill?
    Will

  • #2
    What size is the stud?

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    • #3
      Yes it will do both.
      .

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



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      • #4
        RW about 12 mm haven't measured it
        Thanks John and Happy Birthday.
        Will

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        • #5
          I have no idea as to the availability of equipment in your area, but if someone has a die sinker EDM (AKA ram EDM) that would be your best option.

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          • #6
            It will work a treat. The problem MAY be where to buy it. I had the devil's own time chasing some down. When I finally located it, they would only sell to an established "business," (no walk-ins,) AFTER verifying your credit rating. Also, they would only deliver using an approved Hazmat carrier, (extra delivery charge,) and FINALLY, it would cost $78.00 cdn for 3 litres! Understandably, I did not buy any.
            Duffy, Gatineau, Quebec

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            • #7
              In my shop I have a sign that says:

              Shop rates:
              $50 an hour
              $65 an hour if you watch
              $75 an hour if you help
              $100 an hour if you've worked on it before
              Andy

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              • #8
                A small carbide burr in a dremel may allow you to get a hole into the abyss of broken tools. I've had some success with this over the years. If you can get the engine/engine parts up on a mill you can machine out the broken stuff and then maybe back out the broken stuff. Usually once you get the hole in there it relieves the pressure on the broken bolt etc. and it will back out without to much trouble or if its on the mill, drill it to the proper size to helicoil it.
                Last edited by Robo; 01-21-2013, 10:07 AM.

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                • #9
                  The acid might eat the engine case while it is working on the drill/stud. It could generate smoke/toxic fumes.
                  In an anarchist publication some years ago, a recipe for making some kind of a device for disruption(I can't remember what it was) , included acid concentrate and aluminum to make a terrible smoke. A acquaintance of mine just had to try it out and it was a real experiance not to be repeated. So be careful of using acid around alumminum. At the least ya chance ruining the Honda case.
                  Krutch


                  Mentally confused and prone to wandering!

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                  • #10
                    Sometimes you can break up the drill remnants up with chisel or centre punch, I've done this a few times with centre drills. Darts make good punches.
                    Or try welding a nut on the broken stud, once cooled the Heat should have released the stud, drill the nut out and put a big chamfer on it so you can get a good weld.

                    Brian

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                    • #11
                      Duffy
                      You lot get it cheap, the price I found here was $250.00 for a litre! I have a friend who got me some from work for free. As for an EDM it would be an hour and a half away minimum which means I would have to charge three hours plus what it cost to get done.
                      Will

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                      • #12
                        Forget nitric acid - too hard to get hold of and it's very corrosive.

                        To get a tap, or a steel stud, out of aluminium, use alum. Make a strong solution - dissolve as much as you can in hot water, and let it eat it. It's slow but it's not anything like as corrosive.

                        You can buy it for pickling, or from a pharmacist. The chemical name is potassium aluminium sulphate (British spelling).
                        Richard

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                        • #13
                          Please post a picture. With welding skills you maybe able to build a head on the stud and then with a combination of heating the case and leverage, work the stud loose.

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                          • #14
                            +1 on welding a nut to it and backing it out. I've had good luck with this method in aluminum heads. I used MIG but no doubt other methods would work as well or better. What I found to be particularly amazing was that after the heat of welding penetrated the broken stud it was actually easy to unscrew.

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                            • #15
                              If enough of the stud is still sticking out, cover the engine, expose the stud. Hammer/ twist a nut onto to what is left. When you weld start deep in the nut on the stud. let the heat of the stud heat the nut and weld it. Let it cold completely. At this point I bless it once with a good hit with a hammer strait down on top. This loosen the last of it. Turn it the right direction.

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