I finally threw out my 15 year old chain checker after a Saturday at the Dayton swap meet
I picked up a Park Tools CC-3.2 from a guy's table for $8, mostly because mine had a groove worn in it you could park a car in. He asked me what I was using it for and when I told him I check chain wear on every tune up, he laughed and told me to measure with a ruler instead. I tried it that night on three customer bikes, and two chains I would have replaced at .75 percent were actually fine at 12 inches. One bike I told the owner was good measured a full 1/8 inch long and needed the whole drivetrain. Now I keep a steel rule on the bench and only use the checker as a rough first pass. Anyone else find themselves trusting one tool for years before a stranger at a swap meet makes you rethink it?