If anyone's interested in building their own true cyclone dust collector, Better Homes and Gardens published an excellent article with complete plans, including full size drawings for the sheet metal work, in their November 1997 issue of Wood Patterns. You can download this article from: http://www.bhg.com/bhg/store/product...id=prodwp00068
or, do as I did, go to your public library, have them retrieve this issue from their archives, check it out and copy the entire article. It is actually designed for a bit bigger blower assembly but I scaled down all the plans slightly to make it more suitable for Harbor Freight's 1hp portable dust collector (which is frequently on-sale). As recommended by the article, I used galvanized metal flashing for the cyclone. I'm sure not a sheet-metal worker, but these plans and the directions made it quite easy.