Also crossposted to rec.woodworking
Installing Hardie Plank siding. (Fiber cement combination) Manufacture states that I should use a special blade. Went to Home Depot, and yes, they make a special blade. It is simply a carbide tooth blade with with a total of 6 teeth. 7-1/4 inch diameter.
Can somebody explaing why a six tooth carbide blade would cut any better than, say, a 24 or 40 tooth blade that I use for lumber? I don't understand the physics.
Thanks,
Ivan Vegvary
The 6 tooth will have a more controlled feed cut and run much cooler. I don't know what grade the carbide is or tooth style or kerf set. There are a lot of variable in play and you shouldn't have to do the homework over again. Use the recommended blade.
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While the 6 (or 4 on the blades I have seen) tooth design does help control the chip load, I think it has at least as much if not more, to do with economics than physics. The teeth on the blades made for fiber cement board while mostly carbide, are poly crystal diamond (PCD) faced. You may have noticed that that 6 tooth blade cost more than your 40 tooth wood cutting blade? would you really want to pay 4 times more for 24 teeth? I have cut a limited amount of fiber cement with a wood cutting blade and it worked well enough, but forget about using the blade again for wood. I have also used a diamond wet saw, which, while messy and not spectacularly fast, did give a very smooth cut.
You don't want the abrasive dust rubbing in the cut. The wider gullets on the 6 tooth blade clear the dust easier. The more teeth the more heat you would generate. Yes the special blade is thinner than a standard blade. The carbide tips are probably a special mix to withstand the shock and the heat. They hold up pretty well. The question is, the 6 tooth blades work so well cutting the cement board, why would you use something else?
Those six carbide teeth are faced with polycrystaline diamond
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