Chain: If the chain chatters, produces sawdust rather than chips, or makes curved cuts, it needs sharpening. While the chain's off the bar, inspect its tie straps, rivets, and drive links for signs of excessive wear or damage, then remount the bar and chain when you're ready for filing. The bar should be turned over after every couple of sharpening sessions (this doesn't apply to the newer "antikick" bars that have distinctive prow-shaped noses), and the chain should be tensioned until snug, yet able to be turned by hand. To lubricate the chain, wash it in a shallow pan of solvent to remove dirt and tar, then soak it for 12 hours in a bath of fresh, warm 10-weight motor oil before you reinstall it. (If your bar has a nose sprocket, be sure to grease that also.) The teeth should be sharpened with a round chain saw file of a size compatible with your chain (7/32" and 3/16" are the most common). Chipper chains—the most popular design—are filed horizontally and at a 35° angle to the teeth (in a forward direction) to duplicate the original cuts. Other types of chains—the semichisel and chisel designs—should be dressed at angles 10° below horizontal and 30°, respectively. As an alternative to freehand filing, you might want to consider using either a filing guide or a filing jig, both of which are fairly inexpensive accessories. The rakers—those small rounded nubs ahead of each cutter—serve as depth gauges for the teeth and are generally set about .025" below the top of each cutting edge. In use, the teeth wear down; hence, the rakers must be filed accordingly. A jointer, or depth gauge, made to match your particular chain will allow you to flat-file the top of each raker accurately. Then you can round off their forward corners to complete the job.
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