I was cleaning some parts tonight and among them were the two grease cups for the drive shaft tube. The smaller one had a ring of crud on it that I started picking off before I saw that it seemed to be attached. Was there originally an o-ring crimped onto them, maybe for some friction to keep the cap from backing off?
I believe they used leather.
Thanks Larry. Whatever was on there it's pretty gnarled. I'm going to use it as-is and if I lose the cap somewhere down the road I'll just order a new one.
I found the same thing, and found it to bebleather. I was dismayed to find the normal go-to suppliers don't have such an animal.
It's packing. In addition to keeping the cap from vibrating off, it's so that as you screw down the cap it forces the grease into the bearing rather than out around the threads of the cup.
It is held in place by the upsets made when the hex on the stem was formed. The leather washer must have been placed before the stem was formed. Replacing the leather would be problematical. Stretching an O-ring over the upsets may be possible. Otherwise, go without and wipe off any grease which gets past the threads.
Allan from down under.