by THE SAW DOCTOR
The aluminum circular saw is different to a timber cutting circular saw. The aluminum circular saw has a negative hook angle and the timber blade has a positive hook angle. See the images below.
Timber Blade Aluminium Blade
The timber blade has a positive hook angle to pull the timber into the saw whilst cutting. The grinding angles on the timber blade are sharper than the aluminum blade so the teeth cut the timber fibres cleanly without burning the timber. Timber blades also have faster cutting speeds than aluminum blades. There is more tension in the timber blade. Because of the higher feed speeds when cutting, more heat is generated and to compensate for this the blade has more tension so the tooth edge can be kept straight whilst sawing.
The Aluminum blade has a negative hook angle so the teeth do not grab into the aluminum and bend the aluminum that you are cutting. The aluminum blade is also thicker than the timber blade and it has less tension which makes the saw stiffer and less chance of the blade flexing whilst cutting the aluminum.