In this job I've been round an awful lot of factories - some of them fascinating, some of them, umm, not so fascinating. But the most extraordinary thing I've ever seen close-up is friction stir welding. (The Boeing 777 folding wing mechanism was pretty neat too - and the only thing in Seattle that Boeing flatly refused to let me photograph.)
Airbus UK has been the great champion of FSW in the aerospace industry and they've just confirmed that they're going to be using it in the manufacture of the A340-500 and -600. It will replace riveted joints in a longitudinal fuselage skin join and Airbus hopes the regulators will sign off the process at the start of 2007.
I saw a demonstration at the technology centre of Airbus shareholder EADS in Paris last year. You can see what the machine looks like below - although this is not an Airbus one.
The way it works is that the pieces to be welded are held in place together and the rotating tool bit - which is only about 2cm (1in) across underneath that huge machine - is inserted into the join line and then slowly moved along the line creating the join. When it's removed at the end, the weld is already in place. No fireworks, little heat and next to no noise.
The whole thing looks like magic. What is actually going on, in extremely simple terms. is that the tool 'plasticises' the metal by stirring it, but without melting it. As the bit moves on, the two pieces fuse behind it. Doing away with rivets and panel-overlaps on the aircraft cuts the risk of corrosion and fatigue of course - and Airbus reckons it saves 0.9kg (2lb) per metre (3ft) of fuselage panel joint.
At EADS I wondered if they would even let us look at the bit close-up, and if they did what on earth it would look like. This NASA picture of a similar bit shows just how exotic it isn't!
In fact you've probably got power tools at home with more interesting looking drill bits. How it really works at the physical level I'm not sure, but it was originally invented at The Welding Institute in Cambridge, UK and, if you're interested, they explain here what's going on with some very high quality movies like this one.