This document has lots of useful information on several subjects recently discussed here, including building a work table, cutting and welding tubing, jigging, etc. I'm fairly certain that I got it when someone here posted it in the past, but I was just reviewing it, and thought that I would repost it for those who have not already seen it.
http://www.raptorairworks.com/documents/134-construction-of-tubular-steel-fuselages-v2.pdf
BJC
http://www.raptorairworks.com/documents/134-construction-of-tubular-steel-fuselages-v2.pdf
BJC