The cutting teeth on chainsaw blades must stay sharp to keep the chain passing smoothly through the wood. A properly sharpened chainsaw blade will require little downward pressure to slice through the wood. Unfortunately many things will cause the teeth on the blade to dull, chip and break off entirely.
Mechanics of the Blades
The teeth, called cutters, on a chainsaw blade, which is synonymous with chain, spin around the guide bar at high rates of speed. The hooked tooth digs into the wood and bites out a small chip over and over until the chain meets no more resistance from the wood. This hook, formed by the top and side plates of the cutter, is sharpened at a very steep angle, often around 60 degrees, and does the majority of the cutting work. The top plate, the visible point when looking down, also has another angle set at around 30 degrees that helps slice the wood before the hook scoops it out.
Why They Dull
Chainsaw blades are made out of hardened steel designed to withstand the speeds and pressure of cutting. However, the two main cutting angles undergo a lot of pressure during cutting and will dull naturally over time, much like a shaving razor. Still, the metal can’t withstand the extra force of metal or anything harder than wood. Since the blade moves at such high rates of speed, often around 50 feet per second, when the blade hits anything other than wood, the teeth will bear the brunt of that impact, which will likely cause serious damage to many cutting teeth on the blade.
While the teeth will dull through normal use, hidden objects will help dull those teeth even quicker. Many things can be hidden from the sawyer’s view during cutting. They can be in the wood, for example, a nail from an old fence wire or sign, or they can be hidden around the cutting area, for example, a rock or fence. Sometimes the sawyer may not even see the object before it’s too late. However, take careful note of the objects that may be hidden during the course of the cutting job, and always watch the tip of the chainsaw.
Duff and Dirt
While the damage from metal and rocks may seem like common sense, other things the blade may pass over may not. Duff, the decaying, soft matter of a dead and rotting tree, will wreak havoc on a chainsaw blade’s sharpness. Dirt, should the tip accidentally contact the ground, will also destroy a chain’s sharpness very rapidly. Duff and dirt act much like sandpaper on coarse wood, buffing and smoothing out any surface they contact. When the chain passes rapidly over these substances, the cutting angles will almost instantly be dulled by the extra friction.