Drilling into a material that causes the point to wander? Use a lathe tool to steady things up. With the drill in contact with the rotating work, very lightly touch the drill near its point with a lathe tool held in the tool post – but only supply just enough pressure as it need to stop the wobble.
- When purchasing drill bits, especially small ones, lay the bit on a flat surface, press your finger across the middle and roll back and forth to see if it wobbles. Many drills are not straight, even good-quality brand ones (and especially cheap imports).
- If a drill, especially a large one, leaves “scratches” in a hole, it’s usually because it isn’t straight.
- Need to grind a very small drill ? This can be done by hand – but takes practice and requires the ability to accurately observe what the drill tip looks like. Instead of using a horizontal abrasive surface, hold a very fine India stone vertically in one hand and, with the drill tilted at the correct, stroke the stone up and down. By using 4X reading glasses (or a head-mounted magnifier) even a No. 80 drill can be restored. Find some old drills to practise on.
- Need to restore a badly treated really large drill ? Put the drill in a chuck and grind the tip with a tool-post grinder while it revolves backwards. When both lips have been cleaned up, hand grind the relief a little at a time until you are very close. Finish by stoning. If correctly done the drill should throw equal-sized chips on each side.
- Need to drill a really hard material – a file or even high-speed, all-hard (not just the teeth) power hacksaw blades ? Use ordinary cheap carbide masonry drills and run them as fast as the average drill press will go. The effect is to “heat” the metal on contact and so soften it. Do not be too aggressive; the heat may loosen the brazing that holds the tip in place. Drilling thin sections, like hacksaw blades, will result in a need to re-sharpen the drill after each operation.
- To drill sheet metal (especially brass), or Plexiglass sheet, the bit should be ground vertical on its cutting edges – this helps prevent grabbing when it breaks through. At one time straight-flute drills for brass used to be made.