Long story short: Black & Decker Parana blade cuts through MDF like butter.

A bit longer: I tried cutting through 2 foot of 3/4 inch thick Medium Density Fiberboard. It took about 20 minutes and produced a lot of smoke. It also heated up my 30 year old circular saw to the point that the metal warped, and the metal of a thumb screw broke off.

I went to Home Depot, Lowes, Ace hardware stores and no body knew what kind of blade it took to cut through MDF. One lady said that this blade that only had 3 cutting blades on it would do the job. When I asked her if she was sure, she left that blade and started pointing out a different blade. Uh-huh, she had no idea. Off to find a different sales person and store.

My last stop was an Ace hardware store. He sold me a masonry cutting blade saying that should do the trick. I also bought the Parana blade with medium sized teeth just in case.

I also bought a new circular saw. I tried the masonry blade first. Nada. Worked about as fast as the old blade on the other saw. Tried the Parana blade. Ta-da. This only took me about 3 seconds to cut the 2 foot length.