You may find it interesting that Dufferin was one of the companies approached by Predator to make their low deflection shaft. They of course decided not to make them and the rest is history.
It is 100% caulking with a worn piece of chalk. As a cue repair guy I see this on 10 to 20% of the cues that come in for new tips. I educate the owner and it doesn't happen again.
Its caused by using well used pieces of chalk and screwing the chalk into the ferrule. The top edge of the abrasive chalk sands the ferrule until it has a groove in it.
I have not to my knowledge intentionally blocked a number. I just checked my phone and I have 0 blocked numbers on it. Dont know what happened but try again or email me at masonr@golden.net.
I respectfully disagree. The main reason that tip wear down is from chalking. Chalk is an abrasive. It is like rubbing sandpaper over your tip every time you chalk.
I think the main factor is how often and how you chalk your tip. I had a customer that chalked while thinking what shot to take. He was constantly chalking. I changed his tip every 3 or 4 months. if you give it a quick brush before your shot it will last longer.