I had two Shimano cartridge BBs kicking around my garage, one of which was rather grindy. Rather than throw it out as Shimano recommends and thus waste the precision machining that went into it (and the effort I spent removing it from a scrap frame) I started thinking of ways to revive it.
Step 1: It's Junk Anyway, So...
Anyway, I had the idea to do that same thing to this cartridge ("cartridge being something of a misnomer, see <http://www.bikepro.com/products/bottom_brackets/shim.html> for a crudload of info on that).
It did not turn well enough to use in that state anyway, so it was expendable. Break out the tools!
Please note that I already had thing out of the bike, which required a special spline tool specific to the manufacturer.
I found that the shell of the unit has some kind of coating apllied to it at the factory, which I believe is designed to prevent people such as myself from quickly opening them. The stuff is similar what Wolverine's bones are coated in.
To paraphrase, it took me a good 15 minutes of constant dremeling in one spot, with a conical grinding tip, to get through that stuff.
I think my benchmounted grinder would have made short work of it, but I did not know how thick the stuff was and thus had to be cautious.
Step 2: Drillage
I was not sure how much metal I was going through, and I wanted to minimize the metal bits I would introduce inside the unit, so I drilled slowly, and with much blowing away of shavings.
Step 3: Check for Shavings...
I turned it upside down in case any loose stuff would fall out the hole, then picked up my syringe....
Step 4: THHPPPPTTT
I TOOK A LONGNOSED SYRINGE, and inserted in into the hole I had just drilled. I squeezed, and grease went in. I squeezed some more, and nasty blackened grease issued from between the bearing balls. I continued until clean stuff came out, and wiped everything off. I pushed the rubber seals back in, causing a tiny noodle of grease to come out the side hole, and gave it a turn.
I could not spin it like a top, but it was now free of grinding.
A success, methinks!
Step 5: Sealing It Again
It is good.