Art Martin
ArboristSite Operative
There has been so many threads about filing chisel bit chain and about all the different angles, beaks, hooks positive slopes, negative slopes, gullets, rakers, depth gauges, inside side plates, top outside plates, etc. When you add to that all the different opinions, types of wood, plunge cuts, boring cuts, kickbacks, undercuts, Dutchmen, hingewood, etc. it’s no wonder that so many people are confused. Also, there full complement chain, semi-skip chain, full-skip chain, drive links, rakers, etc.
The first important item that is necessary for precise filing is a vise that holds the tooth firmly without any movement. Filing on a chainsaw bar while attached, results in a sloppy result. Even the slightest movement of the tooth causes an inaccurate cutting edge. I know there are people out there who will say, “I’ve been filing my chain in the woods for years and it cuts fine.” I’ve done it that way myself for years, but I just want to point out the most accurate way. If a chain is worn and the bar groove is sloppy, the inaccuracy of the filing job is magnified. If using a round file on a chipper tooth or a chisel tooth, this is not so important, but on a chisel tooth with a chisel file, no movement should occur.
One of the most important steps to do is to get the correct inside side plate angle correct for the particular wood that you are cutting. Those who are using round files are limited as to the degree that can be obtained on the inside side plate that is trailing, ever so slightly though. The larger the hook or overhang, the more tearing action is created because the top plate is pulling out fiber before the fiber is severed by the side plate cutting edge. This results in a rougher cut and slower cutting speed. You can observe this by looking at the end wall of the log because it is fuzzy. If a person, filing with a chisel bit file, doesn’t make the inside side plate angle more acute than what round file has obtained, then they are wasting their time because it won’t cut any faster. With a chisel bit file, and with a lot of practice, the inside side plate and the top plate angles can be made with single strokes to get a much sharper angles. If you don’t make the correct angles, you might as well stay with a round file. The Madsen’s filing instruction certainly doesn’t have the correct angles for a fast cutting woods chain. There is so much misinformation that makes me wonder who wrote the instructions. With angles like those shown, you are wearing out the cut, not cutting it. You are also wearing out your saw. With a chisel file you can attain 30° or less on the inside side plates while keeping a 30° to 32° outside top plate angle and at the same time, getting a thinner inside top plate angle that helps avoid a drastic chips curl as it removes the severed wood fiber. A blunter edge of the top plate angle will cause more energy or horsepower loss. It’s like a wood chisel removing a chip if you have already scored a board with a table saw, then holding the chisel more upright, it’s like scraping the wood out instead of chiseling it out with the handle lower.
The side plate outside angle, when viewing it from the side should have a 10 percent positive hook (80° from upright). A straight up 90° angle to the bar is OK, but the 10° positive slope feeds into the wood better and has a slight slicing guillotine affect on the cross fiber. I make my chain angle as follows: inside side plate 30°, 10° forward slope on the outside side plate, 32° outside top plate, 34° inside top plate, rakers .025” on new chain and I use the progressive method of lowering the rakers as the chain is filed back. The optimum cutting angle is reduced as the chain is filed back resulting in a smaller chip. To maintain the original new chain cutting efficiency when the tooth reaches the rear rivet, the depth of the raker should be .038”. This allows the cutting edge to enter the wood at the correct optimum angle. Depth gauges should be lowered every time the chain is filed, but this is rarely done. When the “constant” method is used, the gauge reads .025” but as the chain is filed back, the chain becomes less efficient because the optimum cutting angle is reduced. With the progressive method, the optimum raker height is factored in and the chip size remains constant. This progressive method is easily accomplished with a file-o-plate. Even if you have an adjustable depth gauge, the exact amount the rakers should be lowered is hard to determine. A lot of experience helps. Any chain that is filed back, using either the constant or progressive method of lowering the rakers, will cause kickback energy to increase slightly.
I have used skip chain and semi-ski chain during my career as a timber faller and found them to be an advantage when used in the falling process in big timber. As for bucking the full compliment chain is much smoother and faster.
If a beak is created, the top plate acts like a tooth filed with a round file that has been undercut too far. The top plate digs under the uncut fiber and actually lifts and tears out the fiber before side plate has cut it. You should practice to hit the corner exactly at the intersection, to prevent this from happening.
I welcome any questions that might arise about the clarity of chisel bit chain filing or any other questions that you might arise on this topic that I haven’t covered.. I will cover racing chains later in another post.
Art Martin
The first important item that is necessary for precise filing is a vise that holds the tooth firmly without any movement. Filing on a chainsaw bar while attached, results in a sloppy result. Even the slightest movement of the tooth causes an inaccurate cutting edge. I know there are people out there who will say, “I’ve been filing my chain in the woods for years and it cuts fine.” I’ve done it that way myself for years, but I just want to point out the most accurate way. If a chain is worn and the bar groove is sloppy, the inaccuracy of the filing job is magnified. If using a round file on a chipper tooth or a chisel tooth, this is not so important, but on a chisel tooth with a chisel file, no movement should occur.
One of the most important steps to do is to get the correct inside side plate angle correct for the particular wood that you are cutting. Those who are using round files are limited as to the degree that can be obtained on the inside side plate that is trailing, ever so slightly though. The larger the hook or overhang, the more tearing action is created because the top plate is pulling out fiber before the fiber is severed by the side plate cutting edge. This results in a rougher cut and slower cutting speed. You can observe this by looking at the end wall of the log because it is fuzzy. If a person, filing with a chisel bit file, doesn’t make the inside side plate angle more acute than what round file has obtained, then they are wasting their time because it won’t cut any faster. With a chisel bit file, and with a lot of practice, the inside side plate and the top plate angles can be made with single strokes to get a much sharper angles. If you don’t make the correct angles, you might as well stay with a round file. The Madsen’s filing instruction certainly doesn’t have the correct angles for a fast cutting woods chain. There is so much misinformation that makes me wonder who wrote the instructions. With angles like those shown, you are wearing out the cut, not cutting it. You are also wearing out your saw. With a chisel file you can attain 30° or less on the inside side plates while keeping a 30° to 32° outside top plate angle and at the same time, getting a thinner inside top plate angle that helps avoid a drastic chips curl as it removes the severed wood fiber. A blunter edge of the top plate angle will cause more energy or horsepower loss. It’s like a wood chisel removing a chip if you have already scored a board with a table saw, then holding the chisel more upright, it’s like scraping the wood out instead of chiseling it out with the handle lower.
The side plate outside angle, when viewing it from the side should have a 10 percent positive hook (80° from upright). A straight up 90° angle to the bar is OK, but the 10° positive slope feeds into the wood better and has a slight slicing guillotine affect on the cross fiber. I make my chain angle as follows: inside side plate 30°, 10° forward slope on the outside side plate, 32° outside top plate, 34° inside top plate, rakers .025” on new chain and I use the progressive method of lowering the rakers as the chain is filed back. The optimum cutting angle is reduced as the chain is filed back resulting in a smaller chip. To maintain the original new chain cutting efficiency when the tooth reaches the rear rivet, the depth of the raker should be .038”. This allows the cutting edge to enter the wood at the correct optimum angle. Depth gauges should be lowered every time the chain is filed, but this is rarely done. When the “constant” method is used, the gauge reads .025” but as the chain is filed back, the chain becomes less efficient because the optimum cutting angle is reduced. With the progressive method, the optimum raker height is factored in and the chip size remains constant. This progressive method is easily accomplished with a file-o-plate. Even if you have an adjustable depth gauge, the exact amount the rakers should be lowered is hard to determine. A lot of experience helps. Any chain that is filed back, using either the constant or progressive method of lowering the rakers, will cause kickback energy to increase slightly.
I have used skip chain and semi-ski chain during my career as a timber faller and found them to be an advantage when used in the falling process in big timber. As for bucking the full compliment chain is much smoother and faster.
If a beak is created, the top plate acts like a tooth filed with a round file that has been undercut too far. The top plate digs under the uncut fiber and actually lifts and tears out the fiber before side plate has cut it. You should practice to hit the corner exactly at the intersection, to prevent this from happening.
I welcome any questions that might arise about the clarity of chisel bit chain filing or any other questions that you might arise on this topic that I haven’t covered.. I will cover racing chains later in another post.
Art Martin
