Hi Brian. I've been using Osborne rotary punches for years and I've punched thousands of holes and they will eventually break pieces off the cutting edge just with use and I accept that, but over the last 3 months I've had 3 split after just a few holes and one had only punched 2 holes. When I complained about them, the supplier replaced them with no hassle.. The quality seems to have dropped and I even suggested they may be getting them from China as many other suppliers are these days.
I've been using my old Dixon drive punches for 40 years and they were secondhand when I got them and have punched thousands of holes in leather and PVC webbing and have never had one split. The relief inside them is perfect. I did get a new Dixon 1 1/2" punch about 5 years ago and the edges just rolled over, the quality in the newer punches is not very good and neither is the finish compared to punches 50 or 60 years ago.
I've always punched on a pure lead block, it doesn't hurt the punches and there is no rebound or give in it. It must weigh about 25 lb. I remelt when it gets too cut up in an old 9 inch aluminium frying pan about 2 1/2" deep and when it melts I just scoop off the dross and let it cool down and you have 2 nice, flat faces to punch your holes on. Just get some scrap lead and an old frying and you'll have a great surface to punch on! Happy punching, Tony.