I have an inch thick rubber mat I need to cut I want to use my circular saw should the teeth be fine or course?

A jig saw would work much better.

Using a circular saw will cause the rubber to burn and stick to the blade.

Try using an RB knife or a non-retractable utility knife and a clamped down straight edge.

http://www.rbrubber.com/resources/2005%20Tenderfoo...

In the hopes of finding something better in the ole tool chest I came upon a hack saw with a very fine edged blade. We measured out our mats with a chalk line and created a guide by running the carpet blade just once through then while one held the mats the other followed the lines with the hack saw.

It worked in an outstanding fashion and the average time to cut each mat took about 25 seconds. This mats were 6 foot by 4 foot and 3/4 thick. The lines came out sharp and smooth.

1 Inch Thick Rubber Mats

Do not use a circular saw. It will generate too much heat, softening the rubber and creating a major mess if not a fire.

If the rubber is very hard, you may try a reciprocating saw (jig saw type) but I fear this will become too hot as well. Fine teeth blade is best. I am very reluctant to suggest you use this tool.

I suggest you use a shears (tin shears probably) for this job.

How To Cut Rubber

Unless it's really hard rubber, I wouldn't do it at all. IF it's hard enough and you can stop it snatching, then coarse would stand the best chance of not clogging.

You can get knife-blades for jigsaws - that would be a lot better.

http://tooltray.com/DEWALT/DeWALT-DT2201QZ-Extreme...

Or you could just grind the teeth off an old blade and sharpen the edge.

The exact function of a rubber duck is recreation.