Knocking noise when brakes applied

I have pulled drums and inspected the brakes. Found nothing wrong with the brake assembly. Also checked the front suspension, transmission mount, engine mounts, sway bar. Found nothing loose or worn out. Only thing I have found is the face of the drums look, feel like an old 45 record. I presume that is what is causing the problem. I guess I need to find a shop that can do a better job at turning drums which should correct the problem. Thanks for the help.