Hello looking for a scrap metal yard or supplier for an aluminium plate, after seeing some nice duplicator builds at plugfest I have decided to build one myself. Any help would be great. Thanks in advance.

Mid-City Steele and scrap metal...Westport Ma
Shawmet Metal...Swansea Ma
A&E Metals...Fall River Ma

Just a few that I can think of. I don't know where you're located but these are all in my area.

3/8" THICK ALUMINUM PLATE STOCK (http://southcoast.craigslist.org/boa/1617713584.html)

As far as alum goes I would just look around to some metal supply houses, Admiral would be one. Stuff is not real cheap though. As far as scrap yards go I would think it would be hard to stumble across a nice piece of 1/2 thick alum. the size you need but you never know. I'd go with 1/2" min. thickness.

Admiral Metals (http://www.admiralmetals.com/Metalweb/index.jsp)

for info if you are going to use an aluminum base plate and are going to put an aluminum sled on top of it to hold your cutting tool you will need to put a plastic bottom on the sled as alum. to alum. will gall up in a short while, thus no smooth movement. I mounted a thin piece of polyprop. on the bottom of mine. Works perfect. You can use 2 sided carpet tape to accomplish this. I always thought a piece of Corian counter top material would make a good base plate. Also don't forget to get your base up as high as you can so your sled, tool, will not be too high off the plate, which makes it way too tippy , unstable, and harder to control. You are controlling all the movement by hand so you want it as stable as you can get it or your wrists will fatigue pretty fast, especially with hard wood species, plus it will be scary:uhuh:

Thanks so much for the great info guy's, that is a great point about getting the plate as high as I can had not considered that before now. So the quest begins, should be interesting.
Thanks again.

In a pinch, try mcmaster.com