What do you use to cut James hardie siding?

Answer

A circular saw with a hardi blade works well wear a mask its very dusty

Answer

There are several things.
The best thing to cut it with is a fiber cement shear. It's like a set of powered scissors that will cut the material. They're expensive so you don't buy one unless you are a pro fiber cement installer, but they're rentable.
Then comes the circular saw with Hardie blade, which works.
You can also score and snap the material (or so they say), or use a circular saw with a 16-tooth blade, however, you must wear breathing protection because the dust generated contains silica which can cause cancer.




If you are cutting alot of siding and are in a hurry I recomend you use a "Hardi blade" you can cut 7 pieces at once and makes knotch cutting alot faster, but it is dusty! where a mask and goggles, it will "spit", "nippers" fiber cutting shears, are also good as mentioned in another answer but are spendy for a single job. Blades for a saw are about $80 nippers are $200.