Think the 2 hours says 80 % cure, I always wait at least 12 before squaring and 24 hours before turning. I've never had a failure due to the glue since I started doing this. Yes I do sand the tube.I've had a few come loose even with sanding, generally a combination of very hard wood (desert ironwood, ipe), sumo/gorilla glue, and lack of patience (not waiting overnight, I find claims of 2 hr dry time to be VERY optomistic...)