Good idea, thanks! I was going to 'cheat' and use a displacement map but your method sounds much more purist. Will give it a shot.

Does anyone have any ideas about creating welds in poly models? using nurbs I have used the intersect surfaces and then extrude along curve but this doesn't work with polys.

I have managed a few of the bigger welds by duplicating the two intersecting parts and then perfoming a intersection boolean and deleting all faces except for the ones containing the actual join and extruding this to create a box extruding again on the newly created faces. Then I delete the original faces, perform a couple of smooth opearations on the object and then use the sculpt tool to give it some texture. I found that I had a lot more polys than I needed and the reduce function actually led to some nice randomisation further adding to the texture. The whole process takes around 5 minutes (per weld) and looks not too shabby.