On Wed, 22 Feb 2006 23:13:08 GMT, "Wally" wrote:

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.

Yes, that's absolutely true. Those modern metal speaker cones which
you see advertised as 'ceramic/aluminium sandwiches' are actually just
deep-anodised aluminium, as anodising *is* a type of ceramic, hence
very hard and slippery. Best to pilot drill all holes *before*
anodising, then drill out to the required size and use self-cutting
screws to ensure good contact. NB - getting a good electrical contact
to an ally chassis is always a tricky business.

--

Stewart Pinkerton | Music is Art - Audio is Engineering