What TPI changes
Higher TPI reduces the bite per tooth and is useful for thin sections. Lower TPI clears larger chips in thick wood and demolition cuts.
The engagement rule
As a practical starting point, keep several teeth in the material at once. Too few teeth can snag or strip; too many can rub, pack, and overheat.
Why variable pitch exists
Alternating pitch interrupts harmonic vibration and broadens the thickness range a blade can handle.