In article .com, Andy
Evans wrote:
I'm assuming that I should cut out main holes before
anodisation - holes for tube sockets and XLRs for instance. But then I
should drill holes holding the top plate to the chassis after
anodisation so the screws make contact with the aluminium. This sounds
logical doesn't it?

Drilling holes after anodising will only ensure that the insides of the
holes are clean, and there is no guarantee of contact here. You need a
small area of the flat surface around the hole to be clear, so that
washers, nuts and screwheads make contact. There's probably a special
rebate drill that can do this neatly, otherwise it might be enough to use
those spiky washers that bite through the surface oxide. Don't forget to
file away the oxide around the edges of the top plate, and the parts of
the chassis with which it makes contact.

Rod.

Roderick Stewart wrote:

Drilling holes after anodising will only ensure that the insides of
the holes are clean, and there is no guarantee of contact here. You
need a small area of the flat surface around the hole to be clear, so
that washers, nuts and screwheads make contact.

Ah, I assumed the holes were being tapped.


There's probably a
special rebate drill that can do this neatly,

A milling cutter called a slot drill will produce a flat-bottomed hole. If
well centred, it could put a tidy shallow rebate around a drilled hole.


otherwise it might be
enough to use those spiky washers that bite through the surface
oxide.

I'd scrape/sand off the anodising from a small area inside, and fit an earth
point with a serrated washer and tag.


Don't forget to file away the oxide around the edges of the
top plate, and the parts of the chassis with which it makes contact.

Not so keen on that - the filed edges could tarnish and acquire resistance.


--
Wally
www.wally.myby.co.uk
http://iott.melodolic.com