One often-overlooked component of the chainsaw is the guide bar. If it is not properly maintained, it will decrease the saw’s efficiency and damage the chain. Most guide bar problems are caused by one of three things: incorrect chain tension, lack of lubrication, and accidents or irregular operating techniques.
Inspect the bar regularly to insure that it is flat, the rails are straight, and that there is no unusual wear. Every time you clean or replace a chain, flip the bar over. This will insure that normal wear occurs evenly on both sides of the bar. At the same time, run a flat file across the flat sides of the bar to remove any burrs or wire edges from the rails.
Clean the groove with a screwdriver narrow enough to reach to the bottom of the groove to remove any debris before putting the chain back on. With the chain on, check for wear to the groove by holding a straightedge along the bar body and against a cutter side plate. A good groove will hold the chain straight, leaving a small gap between the straightedge and the bar body. A worn groove will let the chain lean until the straightedge is flush with the bar body.
Replace the bar if the groove is worn, if the rails are uneven, if metal on the bar has turned blue from overheating, or if the bar is bent, cracked, or otherwise damaged.
Finally, bar manufacturers recommend that you keep the nose sprocket lubricated. Add grease every time you refuel the saw and keep the grease hole free of dirt and debris. Turn the sprocket while pumping the grease until you see clean grease coming out from around the nose-sprocket teeth on the guide bar. Although bar manufacturers recommend this procedure, many professional loggers feel that excess grease increases the likelihood that sawdust will become stuck in the sprocket, causing damage. Everyone agrees, however, that if you do start adding grease, you should continue to do so every time you refuel.
Tricks of the Trade is provided courtesy of the Forest and Wood Products Institute at Mount Wachusett Community College in Gardner, Massachusetts. Information for this article comes from the Game of Logging training program.