Sharpening Angles Of Square Ground Saw Chain
Listed above are four angle ranges to consider when sharpening square ground chisel saw chain. Small changes in these angles affect how your chain performs. There is no "secret" combination that works best for every professional in every situation. The combination that works best for you depends on the type of wood you are cutting, it's condition, and the power and speed of your saw.
Inside Top Plate
When cutting conditions are clean and the wood is soft, this angle can be around 40°. when the wood is hard or frozen, it usually pays to make this angle more blunt. A blunter angle reduces cutting efficiency, but helps support the edge and working corner for longer running time between sharpening.
Outside Side Plate
This angle should be just under 90°, but not less than 85°. Following this suggestion will make a small back slope in the side plate, which our tests show help chain feed. This small back slope helps ensure the working corner is the first part of the cutter face to contact wood. Any angle under 85° degrees is usually too much back slope. This can make the chain grabby and more difficult to keep sharp. Some people also grind small beak in this area of the tooth. We generally recommend avoiding beaks. See the section on beaks for more information.
Outside Top Plate
This angle should be about 20°. Some operators claim that this angle influences the "kerf" of the cut. They say more angle tends to draw the teeth out so they increase this angle as the tooth wears back. They say this helps make up for some of the "set" that is lost when the tooth is ground back. While this is a good theory, our attempts to measure it have never shown this to be true. Our advice is to grind about 20° and stick with it.
Inside Side Plate
This angle should be around 45°. It can be reduced in clean wood for more cutting efficiency and decreased to help keep a sharp edge when working in hard or frozen wood. On many grinders, this angle is either not adjustable or difficult to adjust. Even when it is adjustable, is is often difficult to grind acute angles without grinding into the side strap and drive link under the tooth. Grinding on these parts often weakens them and chains may break because of it.
We find most pro users grind at angles approaching those listed in the row labeled "Faster Cutting" on the chart above. The reason they do this is most professionals are looking for fast cutting chains and are willing to sacrifice some stay sharp ability for cutting efficiency.