It took DH's muscles to un-screw the center knob. And my sons helped me get the handwheel off. After trying to pull it off, we tried to pry it off with a screw driver, which didn't work. Then we finally positioned a screw driver on the inside metal casing, and smacked it with a hammer. That worked!
The "Before" picture is fuzzy, but you can see the red-ish, sticky, old oil. That is what old oil or the wrong kind of oil looks like, and it feels tacky to the touch. It's just like glue.
To remove the old, gummy oil, I put some WD-40 on it and scrubbed it with an old toothbrush. It didn't get all of it off, so I used a very fine sandpaper to get the rest off. The inside of the casing on the handwheel also needed scrubbing as did the center knob and the position ring.
So, what kind of oil should you use? Only "sewing machine oil." That doesn't include 3-in-1 oil, engine oil, olive oil, or FAX machine oil. And, as you can see, it doesn't include WD-40. We only use WD-40 to REMOVE the old oil.
