"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
. 3.70:

I have MANY (hundreds) of holes to drill in brass of my choice.
(making perf-plates for a pasta extruder).

I'd like some input on what will give me the best surface finish
inside the holes.

The life of the drill bit is important, but not critical. I will swap
a bit every hundred holes if the surface finish is perfect. Also, I
could use carbide drills, and drill 10,000 holes with one, but if that
won't give as good a surface as (say) HSS, then I'll go with the HSS
bits.

Any input?

I've had very good luck with "slow twist" drill bits. I bought a set
years ago, and they are wonderful for brass & plastic. The ones I have
were made by Chicago Latrobe.

One size went missing (25/64ths?) a while back, and I tried to replace
it. I ordered a slow twist drill bit from McMaster Carr, and received a
C-L drill bit, but the twist rate is about half way between normal drills
& the ones in my set. I originally thought they had sent me a regular
bit by mistake, but they checked their stock, and I compared to both
drill types. It's slow, but not that slow.

I don't know if C-L has decided to change the design or what. MSC also
sells slow twists, and the next time I place an order, I will probably
see what theirs look like.

Doug White