I know this doesn't belong in here, but since it's about my EX1, the RedRock microMatteBox, and my newly acquired Tiffen T1 77mm filter - where else should I post? Anyway, here I go with my rather trivial question...

For quite a long time, I kept a rubber lens hood (being a "temporary" solution for enabling the use of RR matte box with the EX1) screwed on the UV filter I've kept on my EX1 lens.

Last night I had to disassemble it, as I needed to replace the UV-haze filter with the T1. And I noticed that the cheap, plastic thread of the $10 rubber hood stuck to my B+W brass thread; so much so that it was extremely difficult to unscrew it! When I inspected the plastic thread, the grooves indeed were full of plastic debris...

I cleaned it carefully and was able to screw it back in on my new T1 filter, and put my RR microMatteBox back on - but I'm aware I'll need to replace the cheap lens hood with a new one (the long promised permanent back step-ring for using the RR matte box on the EX1 will probably never be available :( ).

Here is my question: what sort of grease should I put on the plastic thread so that it doesn't stick to a metal one, and doesn't chip like this?

I would be very wary of using any form of lubricant on a filter thread due to the risk of it finding its way onto the filter or lens.

Have you considered having step ring made to order? For someone with a lathe they are not hard to make and if there is a market for them maybe get a few made. Use an aluminium alloy that anodizes well and get it dyed black.

You could possibly free up your plastic lens hood thread using a metal polish and a preferably old filter with a matching thread. Apply a little polish to the threads and work the two components together a few times. It is very effective on aluminium and is a technique I always use when thread cutting. Make sure you remove all traces of the polish after use. Good luck.

I find powdered graphite works pretty well with plastics, used it to fix the odd lens hood that had the cams jam so the shutters wouldn't move. It seems able to embed itself into the plastic to make it slippery. Need to use a little caution as the stuff can go everywhere but even when I've got it onto a lens it's very easy to clean off. My trick is to apply plenty of it, move the plastic parts around to work the graphite into the surface and then wipe everything down with a cloth moistened with alcohol.
Lithium grease is also very benign, use it in lots of places. The one thing you never want near optics is anything silicon, almost impossible to remove.
I did find an interesting gizmo on Amazon a few days ago, a filter wrench. Haven't got a set (different wrenches for different sized filters) as yet but at $5 for two I think they'll come in handy.

All of that said moulded plastic threads might not be very precise. The shaved of bits are probably from the metal thread cutting out the excess plastic. I suspect this is a once off problem.