[Elecraft] PC BOARD DRILL BITS

[Tom Hammond]

Just a note for builders, especially those who make their own PC boards.

While you CAN use high-speed steel drill bits to drill your 
glass-epoxy PC boards, you'll find that they (the bits) will dull 
very quickly (sometimes within the first dozen holes) due to heating 
(especially when turned at high rotational speeds) and the dulling 
effects of the fiberglass in the PC board substrate.

For drilling holes in PC boards, drill bits made of Tungsten Carbide 
will last MUCH LONGER (typically several THOUSAND holes), even when 
turned at very high speeds.

The problem with carbide bits though is that they are EXTREMELY 
BRITTLE and will break if you even look at them askance, or if 
they're subjected to lateral stress. Run them straight up 'n down and 
they'll last for a LONG time, but apply even a small amount of 
lateral stress and you'll be replacing the bit in a heartbeat. JUST A 
WORD TO THE WISE SHOULD BE SUFFICIENT.

For the past 20+ years, I've been making my own PC boards... in the 
kitchen... with the kind forbearance of my dear XYL, Jeri (K0RPH). 
And I've been using an old Dremel MotoTool, secured in a drill stand 
designed to hold the device, for virtually all drilling tasks. The 
drill stand allows me to run the drill motor (and bit) straight up 
and down, with virtually no lateral stress on the bit (unless I try 
to move the PC board before the bit's fully exited the last-drilled 
hole (bad things happen then!).

I've had problems finding reasonably-priced suitable tungsten-carbide 
bits however. Most new bits run $4-$5 (US) each and I shudder to 
think of breaking one each time I chuck it up into the drill motor.

I found a semi-local source of used bits (but still good for a few 
thousand holes), but I think he's no longer available, so I've had to 
search for another source. Fortunately a friend, Willie, KH6NO/7, has 
found a source of resharpened tungsten-carbide bits in Drill Bit City...

http://www.store.yahoo.com/drillcity/restool.html

While the prices ($0.90/bit) are not those I was paying a year or two 
ago, they're still a LOT better than 4X to 5X that price, for bit 
which will break just as fast, and which won't drill any more holes 
than a resharpened bit.

Just thought I'd bring this to the attention of anyone who might be 
searching for a more reasonable price for their PC board drill bits.

A sharp tungsten-carbide bit, chucked up in a high-speed drill motor 
will go thru PC board like a hot knife thru butter.

Enjoy.

73,

Tom Hammond    N0SS