"Wally" wrote in message
...
Andy Evans wrote:
I'm not going to tap the holes, because I screw through into a
threaded strip under the top plates, usual 2.5mm holes since it's 19"
subrack stuff.
I like the idea of an earth point underneath, though I don't see why
the anodised surface should suffer from drilling 3mm holes in a drill
press - surely this is pretty low risk? .

The risk is a function of your equipment and skill. :-)

I believe anodizing makes a thin layer of the surface harder than the body
of the metal, and maybe more slippery as well - there's always the chance
that the drill could slp before it bites.



You should never attempt to drill metal without first using a punch to make
a little dint for the drill - I use a masonry nail which allows pinpoint
accuracy and then I make a pilot hole with a tiny drill for starters, even
when using the drill press...