This is a two part tutorial I found on Youtube and the links are still active. They demonstrate correct joint preparation and soldering techniques using a length of 3" copper tube, an elbow and lead free solder. It is insteresting to note that they use a water soluble flux, rather than a petroleum based one. I thought these videos might be helpful to those starting out on soldering copper tube and fittings, especially larger diamters.
The third link below is on simple metal spinning of copper to make a dome with the fourth on a similiar article. I have seen simple metal spinning done on a metal lathe and a wood lathe using similiar gear as demonstrated on the production machines used in the video. The gear I saw used was home made and was quite effective, so those with a lathe in the shed might like to give it ago sometime
Soldering 3" Copper Pipe - You Tube Video Tutorials
http://www.youtube.com/watch?v=iCBF6Qgz ... re=related
http://www.youtube.com/watch?v=c9IdKQGj ... re=related
Metal Spinning a copper dome and other items - Youtube
http://www.youtube.com/watch?v=DLuoE_xSMsU
http://www.youtube.com/watch?v=43N44ICy ... re=related
Cheers, Icarus