So what *is* your tolerance? And how are you measuring?
And what is the problem if you get say a .178" hole?

When I want a precisely sized hole, I drill undersize and then ream.

When I drill, I know it is a fairly imprecise operation.

You will spend a lot more on a drill grinder setup then you will on
the occasional reamer.

Anyway, it's a good question. I've seen a bunch of articles (in
magazines, not on the web) that say to stone the trailing edge of
the secondary relief angle behind the floozbub or something else.
Always just with words, never a *good* drawing. Admittedly, this
is an issue that cries out for a good piece of tech writing to
communicate.

Grant

bill yohler wrote:
have enough experience to know that a given-size drill bit (hss) won't
neccessarily 'yield' a drilled hole the same size as the drill bit IS,
due to whatever factors. those factors might be: point sides sharpened
at slightly different angles, or sharpened at same angle but different
lengths. also sides of drill edge 'flutes' worn/abraded...there are
'probably' other causes (which I'm unaware of/please detail).

but, other than 'drilling undersize and reaming', what's the best way
to drill a hole in mild steel and get the 'expected' size hole (aka:
have it yield the _same_ hole size as the bit size)?

I'll be using a BRAND new .177 number-sized drill bit, correct RPM,
and lube/fluid cooling, clamped down in a good drill press. anything
I'm overlooking?

thanks for insights :-)