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I need to expand an existing 6 mm hole to 8 mm, through a thin, but strong sheet of high carbon steel. The hole should be drilled very straight and cleanly.

Can a hand crank drill (such as the one shown here) and regular wood-drilling bits be used? Or do I need to buy an electric drill or some special kind of bits? If the hand crank drill and ordinary drill bit are unsuitable, what tools will I need to get?

  • How thick is the steel? – Aloysius Defenestrate Jun 24 '17 at 14:36
  • You cannot do this with a hand crank drill. Get a decent quality cordless drill and use a 6 mm drill bit designed for cutting hardened steel. You might have to use "cutting oil" to lubricate and cool the material and the drill bit. An ordinary bit designed for wood and soft metals will not drill effectively into hard steel – Jim Stewart Jun 24 '17 at 15:04
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Drilling metal is not a hard problem, but it requires a little more finesse. When you get your tools, feeds and speeds dialed in just right, it cuts like a dream. But do it ham-handed, and you can work-harden the steel. No fun!

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They make combo bits for wood and steel meant for power drilling. A drill bit intended for wood will not work. A drill bit will tend to be rough to control; it won't cut clean or neat. Normally you punch holes in metal with a drill press or punch, e.g. a floor mounted Rotex or turret punch.

Doing it with hand tools is a challenge. Your best bet is a punch, especially since you've already got a hole there. Here's one punch for instance. Drill a pilot hole, assemble it, tighten the bolt, and it cuts the hole. This particular one is for ~20mm holes, but they make them in many sizes.

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If you can get a power drill, I would use a step drill bit to expand an existing hole.

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