I bought a 99k in a cabinet last week....& I never saw so much lint packed in & around a bobbin case (& feed dogs) in my life! Some of it was packed so tight it was actually felt! Anyway, I printed the manual & using the instructions in there I TRIED to remove the bobbin case...it would wiggle around but I couldn't get it out. Pulled as much lint as I could get out around the case....tried it again. Still no go! So I cleaned it up as good as I could with the bobbin case in place. But I'm REALLY picky when I'm cleaning up a machine so, I wasn't happy leaving it like that!
I did a search for "cleaning bobbin case Singer 99" & found your blog. With your instructions for removing the case, it came out after just a little wiggling around! Turns out I did get it pretty clean after all but, there was lint under the bobbin case spring that I'd have never gotten out with the case in there. And I feel much better knowing that, for sure, it's clean.
So again, thanks AA for the great instructions!