Cutting angle is one of the two major angles that describe the position of a tool in relation to a work surface. A cutting angle refers to the angle, in degrees, between the line of the tool and a line perpendicular to the work surface. The other major measurement, tool angle, refers to the angle between the line of the tool and the work surface. As cutting angle decreases the force required to cut into the work surface increases, resulting in a lighter impact on the surface. This means that tools with high cutting angles are used for major material removal and low cutting angles are used for finishing or smoothing.
There are a large number of different angles that affect the way a tool cuts into a work surface. The cutting angle is the largest factor in the final result, but the other angles both influence and cause results of their own. This means that two tools, when used at the same cutting angle, may have different end results.
The tool angle is the second major factor, although most of its importance is located in a small area. A tool has two main parts on its cutting surface, a leading and a trailing face. The angle between these faces forms the bottom section of the tool angle. This subsection is called the clearance angle and every tool must have one. The clearance angle describes the actual impact point between the work surface and the tool, if there is no clearance angle, then the tool is not actually cutting into the surface.
The grind on the blade is the major determination of clearance angle. There are three different types of grind and each has a different overall impact. A flat grind is the basic type, the slopes of the edge are flat like a triangle. This gives moderate durability and moderate clearance angle. A channel edge is convex, meaning the sides bulge out; this gives greater durability but a lower clearance. A hollow grind is concave, meaning it slopes inwards; this gives a lower durability and a higher clearance.
All these factors combine to determine the way the tool cuts. Grind is a major influence on clearance, which will influence tool angle, which will then determine proper cutting angle. Even without all these factors, there are a few basic guidelines for determining likely cutting angles. Generally, when a tool is going against the grain of the surface, a lower angle is needed. A higher angle is used when going with the grain and the highest angle is used for scraping or finishing.
By M. McGee