Professional Saw Chain -
Understanding Cutter Teeth
In the Pacific Northwest, there is one type of saw chain that most professional chain saw users use: square-ground chisel bit. To fully understand why so many professional saw users prefer this chain, you must first understand some basics about chain saw cutter teeth.
Cutter Tooth Shapes
There are two basic shapes of cutter teeth. One style we call: round, and the other we call: square. The images below show these basic shapes. The one on the left is round or "chipper" cutter tooth. The image in the middle is a square or "chisel" cutter tooth. Both are sharpened round. The tooth on the right is also square tooth, but it has been ground "square." This language may be a little confusing, but a study the images below should make these differences understandable. They depict all the basic shapes and grinds that are made.
Which Cutter Is Best?
The answer to this really depends on you. Factors like the saw you run, the work you do, how you sharpen you chain, and so on, all play a part in determining which cutter is best. The following highlights characteristics of each type:
Round Chain - This chain is the easiest to sharpen. An average user can do it with a round file and have good results. It also has the best stay-sharp-ability of the three cutter teeth. Its cutting edge is more durable that those on either square tooth chain. This can be explained by the fact that the edge on a round cutter tooth is larger and better supported.
Square Tooth Round Ground - This chain cuts 10-15% faster than round chain on most saws. Since it takes less power for a sharp square cutter tooth to sever wood fiber, square tooth chain almost always improves a saw's cutting performance. This chain can also be sharpened with a round file, so it is fairly easy to maintain for an average user. While it outperforms round cutters when it is sharp, its stay-sharp-ability is not as good.
Square Tooth Square Ground - This chain cuts 20-25% better than round chain. A square ground chisel cutter tooth is the most efficient of the three. It offers the best cutting performance of all the cutter teeth when it is sharp. This chain can be sharpened with a special file, but most pro users sharpen it with a special square grinder. It is not a chain that is easy to maintain for an average user. Its stay-sharp-ability is also the least of the three styles of cutter teeth.
If you are a professional timber faller working in the Pacific Northwest or Alaska, use square ground chisel chain.
If you use square ground chisel chain, buy a chisel grinder or become friends with someone who owns one. Filing square ground chisel chain is very difficult. Few people do it well. Of those who can file it, most would do an even better job if they had a grinder.
If you cut cedar, salvage, or work in dirty conditions, use round chain. It is easier to sharpen and will hold its edge better for you.
If you are working in clean wood and want the best cutting performance, but can't afford a square grinder, use round ground chisel chain. This chain performs well, is fairly easy to sharpen with a file, and will out-cut poorly filed square chisel chain every time.
This is a close-up photo of a square-ground chisel cutter tooth. The sharp angles and precise alignment in its corner make this a very efficient cutter tooth, but this corner is fragile. It performs best in clean softwood trees.
A Few More Thoughts
The stay-sharp advantage of round chain is mostly seen when working in dirty or light-abrasive conditions. A chain's stay-sharp-ability should not be confused with a chain becoming dull due to "rocking." Hitting a rock or other hard material will dull any cutter tooth -- round or square.
You will notice that harvester chain always has round cutter teeth. This type of tooth works best in this application because a round cutter tooth offers the best stay-sharp-ability. It is also the easiest chain for most operators to hand sharpen. Since harvesters are powered by a large diesel engine, a chain's cutting efficiency is not as big of a factor in cutting performance as it is with hand-held chain saws.