Accurate drilling..

[Greg]

I just posted this pic in a thread over at DIYstompboxes, and thought it might be useful here too.
Best practice for accurate drilling is to make a pilot hole using a Center or Spotting Drill.
They're rigid and much less likely to wander.

[salocin]

I subscribe to the theory of start small and work up. I start most big holes with a 3mm drill bit, then slowly work up to the desired size.

[Greg]

I subscribe to the theory of start small and work up. I start most big holes with a 3mm drill bit, then slowly work up to the desired size.

In general.. starting with a drill like those shown is quite a bit more accurate than starting with a small drill.
It's what they're designed for, and it's why they use them in machine shops, on CNC's, etc.
A 3mm drill is quite flexible, and can wander quite a bit.. especially if it's not sharpened properly.

Also, going up gradually in size can take you progressively off track if there's any variation in material thickness, quality, inclusions, etc... if the work piece isn't absolutely square to the drill bit, or if you don't come down in exactly the same position every time.
You're better to get an accurate pilot hole and then drill to size (discounting Unibits which do a pretty good job, but still benefit from a pilot hole).

[bajaman]

I use a centre punch first
bajaman

[Greg]

I use a centre punch first
bajaman

Yep .. that's a pretty important step too.

[Dr Tony Balls]

I use this order:

center punch > 1/8" pilot hole > desired size of the hole

even if i'm drilling a 1/2" AC jack hole i never have problems keeping things from wandering. i'm using a drill press, though.

[bigmufffuzzwizz]

I use this order:

center punch > 1/8" pilot hole > desired size of the hole

even if i'm drilling a 1/2" AC jack hole i never have problems keeping things from wandering. i'm using a drill press, though.

This is method i was gonna approach it with. But with a hand drill and a unibit!