Thread: Drill grinding weirdness

Originally Posted by ebf

Hey @veitnamcam, so I ground it "normally" the thing looks bloody weird, but did some test cuts like you suggested.

Works fine Drilled a 5/16th pilot hole, and then used the now stubby 1/2

Cuts well, equal chips on both sides. Miked the hole, and came out at .5015, so happy with that...

Most of the time I am drilling holes with clearance for bolting stuff etc so I am generally not concerned with hole size accuracy. But when you want a hole bang on size here is a few wee tips.

Pilot drill but not too big,just big enough to clear the center of the final size drill.
Excessive rake and or too big a pilot while it will cut like hell can cause a hexagaonal over size hole.

And the pro tip, radius the corners of your drill....where the cutting edge meets the flute edge.It essentially turns your drill into a reamer and done right it will cut bang on size untill the flutes get worn and it starts cutting undersize.