Cleaning the Chain & Old Worn Dura-Ace Cassette - Part 2 -- Cleaned three pieces of the cassette so far...

This is the Dura-Ace lock "nut".

I think it got scratched up when I shook all the gears inside the container that I had the parks soaking in with the cleaner...

The threads are actually in good condition.

There's also a very thin wave-spring washer on the back side.

Cleaned this combined two middle gears.

Cleaned one other gear (16 teeth). 

There's still 7 more gears to clean...