1. Remove lens block
The lens was running a little rough, so we disassembled and cleaned it and re-lubricated it. With rubber gloves, the lens barrel can be unscrewed relatively easily by turning it counterclockwise. Pay attention to the metal shims inside.
2. Remove meter scale and locking screw
Next, loosen the three small grub screws and remove the distance ring. Set it to infinity first!
The locking screw prevents the lens from being unscrewed completely. It must be removed.
3. Remove distance ring
Now unscrew the distance ring completely and mark the point where it comes out of the thread. It must be reinserted there later.
4. Re-lubricate and reassemble
After removing the old grease (with benzine and a toothbrush), the focusing worm is regreased. I use a lithium-based grease, which is available from bicycle shops, for example. Then reinsert the worm gear at the previously marked point, replace the locking screw and reattach the removal ring. After cleaning the lenses, screw the lens block back in. Don't forget the shims!