Hey Wreck Wreck, you were right.Difficult to tell from the picture but that appears to be a square thread not Acme, they are different animals. If the width of the crest and the groove between them are equal it is square.
Many OEM lead screws are square.
https://en.wikipedia.org/wiki/Square_thread_form
I did my best to identify it from the pictures, I'm not an expert in threads but have seen and made a great deal of different threads in the last 30 years.Hey Wreck Wreck, you were right.
Pulled this out of my spindle housing. Does it look like it doesn't belong?
Sorry I forgot to post the other half of the equation. There are two. They are in the housing for a spindle that carries two bearings. One was broke and I broke the other trying to get it out. Here's the pic with new ones. There is something really odd about the ones I found inside.That looks like a c-clip, for retaining or limiting the movement of another part, such as a bearing.