Several years ago I got this Singer Featherweight at a garage sale. Well, actually my mom did but it was gifted to me as it needed repairs. The major repair was the hook assembly needed to be replaced. It was missing it's hook as it had been broken. There is a correct position for the hook assembly in the Singer 221 and 222. If it is not in the correct position it could get broken and that may have been what happened to my machine. This is not a cheap part to replace as you will need to find an old one that has been removed from a donor machine. These seem to all run around $70 or so; as of 2011 when I bought my replacement.
Let's see what the correct positioning is supposed to be.
What does an incorrect position look like?
It is simply anywhere other than noon. As that entire piece can move around it means your bobbin will not be properly engaged and your machine will not stitch. Also, as you can see in the image below that hook can swing around and slam into the throat plate from below. It can become damaged or broken.
So the lesson here is take the time to check the hook assembly position of machines you don't know. If you are shopping for one or have borrowed one or maybe you were just given one; take a few seconds and check. Double check the position on your own machine if you have had to remove the throat plate. A few seconds to check will save you money and tears.
If it is in the incorrect position loosen or remove the throat plate and move into the correct position with your fingers. It should move very easily. If it does not then you have some other issues going on and you may need to disassemble or replace the hook assembly.