My experience has also been that the original Weaver gears and sprockets were prone to cracking. P&D has replaced the original weaver parts in their drives. Also replacements I got direct from weaver when they still serviced them worked out fine.
That being said, you still might get a cracked gear or sprocket at some point. Or some other part.
But the beauty of these drives is that yes you can do all the repairs and rebuilds yourself with a few hand tools and some patience. You do not need a metal lathe at all to work on these.
