The Action Of Cutting Wedges. Every cutting tool is a wedge more or less acute. In action it has two operations to perform: first, cutting the fibers of the wood; and, secondly, widening the cut in order that the tool may penetrate into the material, and thus allow the cutting edge to go on with its work. To widen the cut, the fibers of the wood must be pressed apart (the wood split), or the fiber ends crushed, or the material on one side of the wedge must be bent, thus forming a shaving. It is evident that a unit of force tending to drive the edge forward will, under like conditions of material, always result in the same amount of incision. But much less force is required to carry the tool forward when the cutting edge is just entering the material, than when it has advanced to a considerable depth, and, hence, it is fair to assume that this difference is due solely to the resistance that the material offers in opening to make way for the tool, this resistance increasing as the tool goes deeper. The resistance offered to a tool by a bending shaving, therefore, may be many times greater than that offered to the cutting edge by the wood fibers.

An obtuse-angled wedge will cut as easily as a more acute-angled one, but the more obtuse the angle is, the more abrupt must be the turning of the shaving; and since the latter factor is the more important, as regards the absorption of force, it follows that the more acute the cutting edge is, the more easily it will accomplish its work.