Here I shall be showing you how to take apart the rear cluster (that bunch of gears!) from your bike.
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
Equipment necessery will be:
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
Lay your rear cluster out on a piece of cardboard / surface that you don't mind getting ruined and give it a good soaking with your degreaser / barbecue cleaner. Follow the directions on the back but if there are none, then wait 5-10 minutes and wash it off with water from an outside tap, as washing it off in the sink is not recommended.
Step 3: Starting Off
Set up your Dremel with a fine cutting disc, 2mm is about the thickest that can be used on your average cluster. Put your cluster in a vice to hold it tight and horizontal, or alternatively just put it on a surface that you don't mind getting a bit dirty. I stayed on the piece of cardboard used in the previous step so then I could move everything out of the way when we have lunch.
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
Start up your Dremel on a fairly high speed, but not the fastest or the cutting pieces break too readily. Lower it into the large hole down the middle of the gears and start cutting through a layer of rubber (sideways) until you get to the metal pin, and then cut through that. This may take a while depending upon how dexterous you are.
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!
Step 5: Last Pin
Now you should have freed all but one of the pins. You can Dremel this one out, but I have an easier solution. Pivot the gears around so that you can see the plastic bits seperating each one, then break all of these off completely. Move all the gears down one end and depending upon the thickness of your pins, you can either cut it with some bolt cutters, or a hacksaw. I chose the hacksaw method.
Step 6: Finishing Up
You are now done! You should have 6 separate cogs in hand now, possibly a bit greasy but nothing a bit water won't get rid of! You can use these for a number of things, from drive trains to belts!