My post was a challenge, not a complaint. I don't ignore anyone. But I will challenge those that I feel are just blowing smoke.
You need to post a regulation? Go ahead. Nobody stopping you. I still haven't seen it. I will just ask you a simple question first, OK? I would guess I have turned my Freightliner rotors 6-8 times in as many years. I also would guess I have more than approx. 50 brake drums successfully resurfaced. I even screwed one up, when it came loose in the Lathe chuck from chattering. How many of yours were within the published OEM specifications? That's what I thought. Lets keep this light and polite. I don't say much, but when I do, I know what I'm talking about. Otherwise I just lurk - to try to learn a thing or two. Or to be amused. Original poster asked what caused the uneven wear that he noticed. Asked, and answered.
The only thing about checking wear with a tool is you need to know what the original diameter was or maximum allowed diameter. That number is stamped on the drum hidden by the wheel. It's not a one size fits all measurement. That said I replace drum and shoes together. Just my preference
There are heavy duty parts, shoes, drums, and cams, and a mismatch can either make a setup last poorly or break catastrophically. It's a real pain when the drum(s) break.
I had me that 350 Volvo from 1989 brand new intergal sleeper and her brake guts were off the axles and spread over the work bay I took a look at it and it was not doing good. Darn thing only had like 26000 or so. It was good truck. But something must have happened after a recent deep snow delivery. They eventually fixed it and we grabbed another curtain sider and took off for Kentrucky to get Auto Glass for GM Ithink it was.
Lol, was just thinking that... I have a couple drums in the shop, think I will post some pics to help those less familiar. Be safe out there.