Cathy was over visiting tonight. She pulled out her collection of darning feet and darning springs.
We used a couple of them on my Singer 15-90 to see how well they worked. She has one that attaches to regular foot to make the foot into a darning foot. Here is the link to the thread with photos of the darning feet/springs:
http://www.quiltingboard.com/vintage...ml#post5080631