Cassette Disassembly

Cassette cogs can be replaced individually if they wear out. Most cassettes are held together with three rivet pins, however. These need to be removed in order to free up the individual cogs. Here's how I do it:

After removing the cassette from the rear wheel, I centerpunch the rivet heads (so that the drill doesn't wander around). Next I drill each rivet until most of the rivet head has been removed. Next I take my drift punch and hammer the rivets out part way:

You can use something like a long nail if you don't have a punch. Anyway, once these pins are broken loose you can pull them out from the back side with pliers:

All done:

Don't lose the cogs or spacers if you plan to reuse them. The pins are not essential and shouldn't be reinstalled (the cassette lockring will hold everything in place). Also if you're replacing individual cogs, try to get replacements from the same cassette group (Shimano cassettes have their group designation stamped on each cog, like ac, e, w, etc.). If you use mismatched hyperglide cogs, the shifting might be noticeably worse on those cogs. This method doesn't apply to high end cassettes like Ultegra or Dura-Ace though, since the cogs are mounted to aluminum carriers and aren't individually replaceable.