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Broken drill

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  • Broken drill

    Ok, I know I should have taken pictures first, but I really didn't think I would have much luck on this project.

    A friend/neighbor brings me some 1/2 X 6 flat bar to cut into 6" lengths and then drill some holes in for some project he is working on. I am not in the shop at the time so he throws the bar in front of the door and leaves. "Oh, by the way, I also left a broken drill bit, can you fix it?" says he in the subsequent phone call,

    Broken drill bit?? Dammnit, do I LOOK like some relative of Houdini?

    It is a brand new S&D, 23/32", but not with a broken shank. This one is broken about 3/4" below where the shank meets the body of the drill, right through the twist. Seems to me to be a really difficult way/place to break a drill bit, but he didn't give any explanation, so what do I know.

    What the hey, I can't make it any worse so how to attempt? I have had good luck in the past making long extension twist drills by silver soldering a piece of drill rod onto the shank of a standard jobbers length drill, so lets try that. I wanted to just shove the two pieces back together as is, as this would at least help achieve some semblance of alignment, but of course he had apparently been using cutting oil of some kind so the fracture was thoroughly contaminated.

    So,off to the belt sander for a minimal grind on both pieces to achieve clean surfaces. Find a small piece of 1"x1" angle iron and try to clamp the two halves in some sort of alignment. The first two tries end disastrously as the Vise Grips don't pop off until after I have applied some heat, scattering the by then hot drill bit pieces, angle iron and clamps across the floor and under the welding table.

    Ok, finally get a lash up that survives the application of brazing heat and apply copious amounts of flux, and then some solder. Well, does that look ugly or what??

    Douse the abortion in some water and clamp the shank in the vise and tenuously tap sideways expecting an immediate pop off. No?? Ok, tap harder to where I am thinking that something is about to bend. Still no pop off.

    Spin in the drill press to see what the alignment looks like. I can hardly believe my eyes. I can tell that it is not perfect but it could easily be within .005"-.010" TIR at the point. Grind on a new point and drill two holes through a scrap of 1" steel plate, hole sizes are .728 or about .010" over the .7188 original size, checked with a plug gage.

    Miracles do happen, as I was there when this one happened in my shop tonight........


  • #2
    Why didn't you degrease the pieces instead of grinding and increasing the chance of misalignment? But hey, it worked, so don't complain!
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