Aluminum support rails (for round linear shafts) typically sell for upwards of $5.00 per inch, or a whopping $25.00 per pound of aluminum!

Being the cheapskate that I am, I decided to make my own.

I negotiated for some scrap aluminum castings at work, about 50 lbs.
Still waiting for the owner to confirm my offer of 50 cents per lb.
He's a very busy fellow...

I created a pattern from some 6061 flat stock and delrin.
The casting flask was made from poplar.
The cope and drag were then rammed with Petrobond sand.

The aluminum was melted in my homebuilt 3500 watt electric furnace, using a clay graphite crucible.

Here's a pic of the result. One rail is as cast, the other has been lightly machined. The rails are about 15 inches long, will be trimmed to 12 inches.
I poured 6 of these, all will be machined to +-.001 on height.

http://i201.photobucket.com/albums/aa145/Eurisko_CNC/Rails.jpg

Still getting some surface porosity, but the rails will clean up nicely.

:)

I should add that these rails will be used in either a 48 in. x 36 in. OR a 36 in. x 24 in. router.

The build will be steel and aluminum.
I'll be using thomson open pillow blocks, some thomson case shafts, and some stainless steel shafts.

I have (4) 282 oz. steppers, (4) drivers, and (2) 24 volt power supplies.
18 feet of 1/2-10 acme threaded rod, delrin nuts, angular and deep groove bearings.
Plenty of 6061 plate.
24 feet of 1 x 3 steel rectangular tubing.

I've been debating the size of this thing.
Given the motor and leadscrew limitations, should I even consider a 48 x 36 router or just be content with a 36 x 24 ?

Ideally, I'd like to do some light metalcutting with this.