Spamlet wrote:
"Dave Osborne" wrote in message
...
Dave wrote:
On 10/10/2010 11:40, Will wrote:
Anyone know why you can't buy diamond drills - I have a diamond saw but
the
hardest drill I have is HSS Cobolt?
There are 3 drills harder than that, but you will have a hell a lot of
trouble tracking them down. Even Dormer do do not list them.

C1150 come next with
D200 following
Solid tungsten carbide was used for drilling carbon fibre.

Dave

Good point. You can buy solid carbide drills for drilling printed circuit
boards.

http://www.megauk.com/carbide_drill_bits.php

which always sounds odd because pcbs don't seem that hard - but I suppose
they are full of glass these days...

S



Yes, the common professional quality board is FR-4, which is made of
layers of glass fibre mat impregnated with epoxy resin.

http://en.wikipedia.org/wiki/Fr4

The thing about drilling circuit boards is that you need the hole to be
perfect every time. Commercially, boards are drilled clamped between
sacrificial substrates so that there is no surface spalling on entry or
exit. Also, they drill at very high speed, so as soon as the sharpness
of the drill goes off, it tends to burn its way through. PCB drills have
a limited life because of the glass content in the PCB, but solid
carbide drills lasts much longer than HSS.