I can upon a problem in our shop. We had a good mill and a couple of vices, but no way to hold plate stock and do perimeter work. I called our local Al supplier and priced out a piece of .750 x 20 x 20 6061. $250!!!! I new I could have my cake and eat it too without thrashing my wallet that hard. ;)

So I started thinking.
Why do I need a fixture that thick - for strength and accuracy and to allow for tapped holes to hold down parts.
Why Al - don't want it to rust, or rust the table to which it is secured.

My solution was to get a piece of HR mild steel .750 x 20 x 20 and then make a sandwich with some .190 5052 Al that I had acquired cheaply.

To do this, I deburred all of the edges and bought a couple tubes of JB IndustroWeld. I spread the epoxy out on the plates with a trowel (the toothed tile laying type). I prefer the toothed type so that I could get an even coat. I then put the sandwich - Al on Steel on Al in a vacuum bag and hooked up the pump (rotary vane type) for 6 hours. This nicely squeezed all of the plates together and made one very nice hunk of metal.

http://www.cnczone.com/gallery/uploads/33492/0501070858aM.jpg

After 48 hours I took the fixture back to the shop and then fly cut both sides. After I finished fly cutting, I bored and counter-bored holes for the bolts in the t-solts and holes for the precision dowel pins (allowing for quick zeroing in when r and r'd from the machine.) When everything was secure, I ran a program and cut coolant channels into the perimeter to keep things flowing nicely.

Can you say squiiiiished?
http://www.cnczone.com/gallery/uploads/33492/IMG_4582M.jpg

http://www.cnczone.com/gallery/uploads/33492/IMG_4581M.jpg

I believe that this fixture has given me everything I could ask for (strength and durability along with resistance to rusting.) I have been using this for 6 mo now and it has been awesome.

J

Good idea!

Necessity is the mother of Invention, and, as everybody knows, a skinny woman named Poverty is the mother of Necessity.

Hager

I was interested to see that you have been using it for 6 months. Good for you. My first thought on this design was thermal expansion differences. If your shop took a big swing in temp, would the plate warp? Would it delaminate? But I guess not, good fix.