Re: [CAD_CAM_EDM_DRO] Granite router/mill

Bob Muse wrote:

>Look for an old CNC PCB drill. They are built just like you describe and
>slide on air bearings. Probably be good for routing aluminum, don't know
>about milling especially in steel. They can sometimes be had for free or
>really cheap--they are heavy though.
>
>

The machines in question are Excellon PCB drills. They sold for $100,000
in the 1970's, and run about $250,000 today. They use TONS of granite.
I think the main table (5' x 5' x 8") is 7 tons, and the legs are 1.5
tons each.
There is a bridge across the top that is also granite, the drill
spindles are
attached to that. There is one granite beam glued to the table. A
cross-piece
slides over that on 4 air-bearing slider pads, and a 2nd axis granite beam
slides in the upper part of the cross, again on air bearings. A work table
is attached to the 2nd axis, and rides on air bearings on the main table.

I don't know if this design is really applicable to a router, but with good
chip extraction, it could work. They are fantastic machines, but maybe
heavier than the OP was looking for. I don't know what size router he
was looking for, but even small surface plates get heavy. I have a 24 x 36"
plate, 3" thick, that weighs 270 Lbs, I think.

Jon