I don't know why they'd build the arm with a fiber ring in the arm instead of a good brass (or other metal) ring...
I had a discussion with a buddy today. He's a manufacturing guy, and machinist .
His answer was that you don't want to damage the expensive screw.
So, I guess the wear is taken by the cheaper nut.
That would certainly be a problem if you used a steel nut.
And if my ears didn't deceive me, that's all the local industrial hardware store had: steel.
I had high hopes to find your part for $3 ... $5, and ship everybody two.
I'm not a mechanical guy, but if I'm not mistaken it's
Delrin you would want in the nut, not nylon or fiber.
I'll talk to some materials experts and get a better idea.
Teflon would be nice, but might be too soft, and most likely way too expensive.
As a last resort, I wonder about custom-making some of the replacement nuts?
My machinist seemed pretty interested, if he could use a fairly soft material.
So, if anyone has a worn-out motor they'd like to contribute to the cause, I'd be happy to pay shipping.