Explanations of Saw Chain Sharpening

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	The top corner of the cutter is the most important. This part of the tooth cuts one end of the fibers, then the top plate of the tooth bends them up from the rest of the wood. The next opposite cutter that cuts cuts off the other end of the fiber and its top plate lifts out the chip from the rest of the wood. Therefore, make sure that the corner is perfectly sharp! (The cutter in the illustration is much too dull!) And if the you keep cutting when the corner is not sharp, it will quickly be dulled to the point that you will have to file a lot off of the chain to restore it to its proper shape. Keeping the chain razor-sharp is important to long chain life.
	Some chains are rounded, rather than come to sharp corners. They don't cut as fast, but they don't dull as quickly in conditions with lots of dirt, either.
	The opposite extreme is square-filed chain. It cuts the fastest of all, but must be filed with a specially-shaped file or ground with a special stone. Either way, most loggers feel it's more trouble than it's worth in all but the largest wood.

Only about one-third of the cutters cut at any one time. The cutters are all dancing up and down, and it's a random chance as to which cutter will dig in and cut --- which is why the depth gauge must be set so that the cutter that does make contact, does so at the correct angle to pull itself into the wood properly.

The depth gauge controls the angle that the cutter meets the wood. The cutter must meet the wood at the proper angle to pull itself down into the wood. When it does, it will be out of line with the rest of the chain, which will then pull the cutter back out --- thus cutting one side of a chip. This action is similar to the way a ship pays out heavy anchor chain to get the anchor at the proper angle to pull itself down into the sea floor. Winching up the anchor line will tilt up the cutting edge of the anchor, freeing it so that the ship may proceed.

Originally, chain saws were gear drive and the chain moved slowly. The operator pushed down hard on the bar so that the chain was riding on the bar as it cut. Not so today.

In those days, the depth gauges were filed with a jointer, which made the distances from the tops of the cutters to the tops of the depth gauges equal. Remember, today the chain is not pressing on the bar as it cuts, so we want the angle of the cutters to the wood --- as set by the depth gauges --- to be proper. And you can't get that with this older type of depth-gauge-setting tool.

A depth gauge file is a flat file that has smooth, rounded edges so that you won't do too much damage if you slip.

On a crosscut saw, there are rakers, a type of cutter that chisels out wood fibers after the fibers have been cut on both ends by the cutters (or "pegs"). Then the rakers carry the chips out of the cut. (The raker is in the center here, with a left and a right cutter on each side. Some saws have two left and two right cutters between each raker.) Originally, chain saws had teeth (cutters and rakers) like a crosscut saw, but it takes both time and skill to file them, so the more easily-maintained chipper chain won out. As far as I can find, during the time when crosscut saws were still used no one confused a raker with a depth gauge.

For example, can you believe that the depth gauge shown can a) cut fibers and b) push the chips out of the cut? (Actually, the chips must ride within the cutters themselves.)

Electrolux, a Swedish company, is probably the largest manufacturer of chain saws in the world --- if you count all the companies they have bought: Husqvarna, Jonsereds, Partner, Pioneer, Poulan, etc. If you count just one brand, the German firm, Stihl, is probably the largest under one name. And, yes, Electrolux is the vacuum cleaner outfit ... at least outside of the U.S. In the U.S, they sold the name, so that an American Electrolux is not an Electrolux. Or some such thing. Today, you need a scorecard to tell the players!