My Sweetie picked up another 15-91 yesterday. In need of a little love and service, it got my full attention today. Here is the machine being broken down. As I separate the parts, I place them in containers with a little simple green. They then go into my ultra-sonic cleaner. Once they are finished, I dry and separate into small container drawers. Next I clean, service, oil, and grease the machine (including the motor). Then begins the process of reassembling, polishing, and finally testing. Below is a picture of the finished machine. The next series of photos are the process I use to clean and keep organized. Finally, you can see a video of the stitch test and the bobbin winder test.