10" blade for polycarbonate?

[Phil Thien]

Getting some conflicting information.

I would like to cut some polycarbonate. I've cut it before using a 40-tooth carbide-tipped GP blade and a reasonable feed rate.

While the cut quality was fine, there were some "popping" noises I always attributed to the positive hook angle on my blades. It isn't a reassuring noise, it sounds like the teeth are grabbing or catching the plastic, rather than cutting it.

So this time around I thought I'd investigate and found many people that said to use a negative hook angle. Which makes some sense to me.

OTOH, there are plastics blades being sold (by Olshun, for example) that have a positive hook.

Who's right here? Positive or negative?

Also, what is best for cutting aluminum. To my way of thinking, the best blade for cutting aluminum would also have a neg. hook. Or am I wrong? I'm wondering if I find a good blade for plastics, whether I may have a good blade for aluminum, too? I've cut aluminum with my 40-tooth carbide GP blades, but wouldn't mind having the right blade for the job. And if it is also the right blade for plastic, so much the better.

Finally, any good deals on blades out there for this? Specific blade suggestions would be welcome.

Thanks!

[Steve Wurster]

I have this blade, or at least I think it's this blade. I cut polycarbonate with it once and it seemed fine. The cleanup from all the little shavings due to the generated static electricity is annoying, but that's what you get cutting something like this. Anyway, it says it has a negative hook angle. It also says it's not recommended for non-ferrous materials (like aluminum). So far all of the aluminum I've had to cut I've done with a hacksaw.

http://www.amazon.com/Freud-LU94M010-10-Inch-Plexiglass-Plastic/dp/B00004T7AL/ref=sr_1_1?ie=UTF8&qid=1342113019&sr=8-1

[Peter Kelly]

I've got separate non-ferrous metal and plastics blades, both from Everlast. The metal blade has a -2° hook and the plastics one has a 5° hook. The plastics blade starts to grab a little when cutting thicker 3/8" pieces or when the teeth start getting dull.

[Jerrimy Snook]

Most general purpose (meaning will cut most plastics fairly well) plastic cutting blades are zero or slightly negative hook. Same for aluminum cutting. Specific plastics cut better with positive hook triple chip or alternate face bevel blades. It all depends on what your cutting, the type of machine you have available, and the cut quality that is acceptable.

How thick is the material you are cutting? The thickness determines the desired tooth count. Less than 1/8" use 100 teeth. 1/8" to 1/4" use 80 teeth. 1/4 to 1/2 use 60 teeth etc. There are many thin blades available that will cut aluminum and plastics. Freud has a Diablo (sorry I don't remember the part #), Matsushita has the MS10080AP (http://matsushitaamerica.com.p4.hostingprod.com/aluminum.htm), Tenryu has a couple, the AC25580DN (http://tenryu.com/ac.html) and the IA25580DN (http://tenryu.com/ia.html).

Disclaimer: I am a tooling dealer and represent Tenryu, Matsushita and several other brands. I hope to provide information only.

[scott spencer]

Phil - I haven't cut enough plastic to tell you what causes the popping noises, or to even give an informed recommendation, but I know that heat is an issue. Most of the better 40T general purpose blades (WWII, Gold Medal, Super General, Fusion, TS2000, etc) have tight side clearances to give wood a polished edge, but that also causes more heat in plastic. I'm wondering if a 50T ATB/R combo blade might give better results because they tend to have more generous side clearance geometry.