There are special devices for sharpening dull or broken drill bits If they are not at hand then try under a rotating drill bit set suitable abrasive (e.g. abrasive wheel) at an angle of 30 or 45 degrees — and the drill will self-sharpening.
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Not to dwell on his haunches (if you planted seedlings in the garden or in the greenhouse, laid out by a car repair) — for any "knee" work your good helper will be here is the seat box. ...