This is a fairly frequently asked question, but is difficult to explain in words.

I've drawn the diagrams below in the hope that it will help.

Although the subject of sharpening drills is HUGE, what I've drawn below will do for 99% of holes through most materials, especially mild steel.

If it doesn't work so good on a particular material, try making the drill bit more or less pointy.

If the drill bit keeps going blunt, slow down the drill speed.


And my top tip for easier drilling with big (>10mm) bits:


Si

Good post Si. Not seen the concave/convex tip before, thanks

Nice one Si, I hope this makes it to the Technical Archive

Web thinning should also be considered when a drill is getting shorter due to regrinding as the shorter the drill the thicker the web gets, giving a much greater length chisel edge which in turn creates more heat and requires more power to drive. Be carful when thinning the web (reducing the chisel edge) it is not unknown for the drill bit to split vertically up the drill if the chisel edge is too small.

Cheers!

People have talked about drills splitting up the web - but I've never seen it! Must try harder!

Agree re the web getting thicker along the length of the drill - but figured most people will loose or break the bit before it becomes an issue & decided to keep it as simple as possible!

Si

Nah me neither - thats a good tip <groan>

I sharpen my drills on a linisher, I find it a lot easier than the side of a grinder wheel.

I used to work with a guy who could grind a ø6" drill to perfection on a linishing belt, and then add chip breakers and web thinning with a 1mm grinding cut off disc!