Wood – Mitre Circular Saw blades for cutting Oak floorboards

The difference between a 10" 60T and 80T saw blade is only slightly noticeable. In practice, chip out with either isn't a huge concern, provided you go slow. An 80T blade is naturally going to slow you down more, so that may be useful if your tendency is to yank the radial arm down and go.

Another consideration is the end grain of the piece, some trees are just flakier than others, in that case an 80T is a safer bet.

Teeth aren't the whole story. If you throw a crosscut table blade on a miter saw it might have a tendency to feed faster than you want. If you get a miter blade then there's not a ton of difference. The miter saw blade teeth are back angled a bit to avoid pulling the arm in on you.

So the safe bet is the 80T miter blade, but I'd be surprised if a 60T gave you any trouble.

Back in the day when I used to put up vinyl siding, I found that the best way to cut it with a circular saw was with a cheap 140 tooth plywood blade installed backwards (to give the teeth a negative rake and prevent chipping):

For really hard plastics, I've used a diamond abrasive blade before and that did a great job (these are incredibly expensive if we're talking about a single cut though). I would imagine an abrasive blade for cutting metal would do just as well though:

You should be able to pick up either of these for less than $5.

Wear good safety glasses and do a trial cut first with whatever option you go with - plastic will chip long before it will bind the blade in most cases, and these can be both sharp and high velocity.