I've been routing out 6mm (well, 6.7mm, but hey ho) dadoes to slide in cabinet backs and drawer bottoms. Having just broken my bit, I did a bit of work to see what might be the problem. My collett seems ok, and there aren't any worrying marks on the broken bit (it's a trend 6.3mm double-flute bit with a 1/2" shank), so I'm going on the assumption that I was putting too much stress on the bit. From reading around, I can see why a single flute or better yet - a spiral down-cut bit would be much faster, cleaner and more efficient. However, I'm at a total loss to find a reasonably priced bit that will do ~6mm dadoes in a 1/2" shank. I could simply swap out to a 1/4" shank as my router (the Hitachio M12V) has both, but I'd much prefer to go with the larger shank for more stability etc. Am I missing something here? I'd figured this would be a pretty typical piece of kit given how often 6mm plywood serves as cabinet pieces!