On Tue, 15 Apr 2008 17:38:48 +0100, pentagrid wrote:
....
It's pretty easy to learn how to hand sharpen a drill
and lots of advice on this has been posted.
....
A drill can only produce its nominal size hole if the
drill point geometry is precisely symmetrical. It's reasonably easy to
come close to with a well designed drill jig but nearly impossible with
a freehand drill grind.

Can you gaze at your freehand sharpened drill point
geometry and be sure that your efforts have produced a point with
asymmetry less than 0.005"
....

I'm sure the answer to that question is yes. 0.005" is easy to
see by eye. For example, if someone hands you a #11 and a #12
drill bit, about .002" different, you don't have any trouble
telling which is larger, do you?

-jiw