Park CT-3 Screw Type Chain Tool
Made from investment cast tool steel. The CT-3 features a handy "loosening shelf" to remedy stiff links after reassembly. The fine thread and comfortable size enable easy removal of even the toughest chain rivets. Like all Park Tool Chain Tools, it's easy to use and built to last, and has a replaceable driving pin. Works great on derailleur chain, even 9 and 10-speed chains.
Buy a Shimano TL-CN32 instead. The 32 has an independently rotating pin which drives rivets in and out with rotating. Rotating is bad because it widens the holes in the links and compromises the integrity of the chain.
I have used this tool on a couple of different speed chains and leaded it to a couple of friends with out any issues. The only reason I gave it four stars was because of the price.
Every time I've used this tool, I've broken the pin that is supposed to pop through the chain pin when you tighten it. I've taken it back to the bike shop and had them replace the pin in the tool 6 times. Each time, I've asked detailed questions to be sure that I'm using the tool the right way. I'm done with this tool. I threw it out and I'm going to use my heavy Topeak multi tool with an allen wrench. At least it doesn't break.
So Smooth and easy to use. Does a great job even on old rusty chains.