If you do not want to ream, I would pre drill with a slightly undersized
bit and make the finish pass with the fresh factory drill bit. If you
get good results, continue to duplicate all conditions for all holes.

--


Keep the whole world singing. . .
Dan G

(remove the 7)



"bill yohler" wrote in message
om...
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 :-)