Lee Valley sells good metal grinding belts for 1x42, I am sure others do also, but they are 6 miles from home for me. The "purple" and "blue" belts, etc..., are not standard items from most suppliers.:

http://www.leevalley.com/US/wood/pag...40&cat=1,43072

A lot of the knife guys use Pop's. I try to get stuff inside Canada when I can since shipping on these big floppy belts is not cheap. So I haven't tried Pop's myself. When you upgrade, always go to a 2x72 system since all the serious stuff is made in that size. I am sure industry uses many other sizes, but as far as retail is concerned, that is the size.

http://www.popsknifesupplies.com/

Money spent on belts that are more expensive/better quality is alway money well spent. And fresh belts should be used for any critical or production cutting. However, to keep costs down, it pays to be careful to not take a sharp piece of metal and just knock all that expensive grit off the belt. Knife guys keep dull belts around for cutting in, since that process will rip grit off until there is enough bearing. Tube joinery is pretty severe, so for that I would use the cheap brick coloured belts. A powerful variable speed motor also extends belt life by optimizing surface speed/feed.

Just to see what the grinders can do look at the following tape profiling in 1:20-3:20. Keep in mind that people buy custom knives in part to get tool steel blades that are ridiculously wear resistant. If this was 4130, it would swallow that metal like it was hardly there.

http://www.youtube.com/watch?v=kvlKfzW12d0

5:20 shows the blade plunges.