If you're wondering what you'd do with this
I'd recommend www.instructables.com/id/Bike-Tire-and-Gear-Belt/# this Instructable, it's really cool.
There's also www.instructables.com/id/Make-a-Clock-out-of-a-Bicycle-Brake-Disc/ for the DIY lover!
Step 1: Materials
A rear cluster from a bicycle. I got mine from the back of a bicycle store in a big bin full of metal.
A Dremel or other spinning cutting tool with a nice skinny blade.
Degreaser / barbecue cleaner. Grease on your hands for the rest of your day may just cause female relatives to faint.
Safety specs. To protect your peepers from flying cutting discs.
Gloves. Not necessery but useful for keeping your hands free from what the degreaser does not get. I didn't use them, and paid dearly for it.
A screwdriver for a bit of leverage where necessary and changing the cutting disc on your Dremel.
A hacksaw. Makes finishing off the last bit of cutting so much easier.
A vice to hold it when cutting. Not necessary but definitely useful.
Step 2: Degreasing
Step 3: Starting Off
With the side with the smallest cog / gear up, identify the rivets holding it all together. On mine there was three, but depending upon which one you get there may be more. If you have a choice between a couple of rear clusters, go for the one with the least amount of these rivets.
Now look down the large hole in the middle of all the gears / cogs and you will see that these pins go all the way down through. You will also notice that separating each of the gears / cogs is a rubbery plastic circle. This is what we shall be cutting through, and then the pins.
Step 4: Cutting Through
You should be able to understand, but if not, refer to the exquisite and highly detailed photographs.
After cutting through, pull the pin out and repeat, sometimes the pin is a bit hard to get out but a hammer can help, but it's not often necessery.
Just remember, leave one last pin uncut!