Rick:
I take it then you approve of my selection of sizes ;-)
Sorry, I should have mentioned in my post that I have several Dremels plus the small Dremel drill press type holder. Hopefully I should be OK in that department. I have used it in the past for drilling PC boards with HSS bits without issue but this would be my first attempt at using carbide bits so I hope there won't be too much side play. The holder is an older one, about 20+ years old. I thought I read somewhere that their newer ones aren't as well made.
I'm thinking in terms of getting some carbide bits plus a bunch of HSS bits as backup just in case. KBC carries "made in the U.S." carbide bits with 1/8" shanks for only $4.75 a piece. Their small HSS bits are either $0.47 (probably far eastern) or $1.61 (probably U.S. made) each depending on finish, so I could get a bunch of those without breaking the bank.
Cheers,
John
--- In Homebrew_PCBs@yahoogroups.com, "Rick Sparber" wrote:
>
> John,
>
> I just went through this myself. It sounds like you have figured out what
> you need. I ended up spending $60 on a nice selection based on what my
> current circuit board needed.
>
> Let me ask a related question - what do you have to drive them? Assume you
> want to run at 200 surface feet per minute. Then the needed RPMs equals
> 200/(0.26 x D) where D is the diameter of the drill in inches. Given your
> 0.020" drill you are looking at 38,500 RPM which is about what a Dremel(r)
> puts out. The mount must have very little side play because that can snap
> these tiny drills too.
>
> Rick