Homebrew PCBs

John,

I only recently started to use these tiny tungsten carbide end mills. They
work much better than twist drills and I've been told that they don't dull
nearly as fast.

The end mills I bought came from 

https://www.drillbitcity.com/catalogue/10_piece.asp

I bought 5 different sizes in sets of 10. They came custom labeled in one
box. Since they are re-sharpend, the price is much less than new yet they
work great. I was pleased with this company and will use them in the future.

Rick 

-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of thb201
Sent: Sunday, January 13, 2013 12:34 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: What size drill bits?

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




------------------------------------

Be sure to visit the group home and check for new Links, Files, and Photos:
http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links