Abstract: A router bit body has an open center space that permits plunge cutting and that facilitates the ejection of chips from the router bit body. The knife is screwed to a sloping knife-supporting plane surface that underlies and reinforces the knife and that reduces the stresses in the mounting screw. The knife-supporting plane surface lies in a plane through which the angle of rotation passes obliquely.

Abstract: A router bit having an adjustable blade for cutting various widths of grooves includes a mechanism for maintaining static balance about the axis of rotation for all positions of the cutting blade within the range of adjustment. The router bit includes a main body adapted to be held and rotated by a chuck, and which includes a bore whose axis is parallel to but displaced from the axis of rotation of the main body. An arbor with an offset cutting blade is adjustably mounted in the bore, and the width of the groove is determined by the angular position of the arbor within the bore. However, such adjustment alters the static balance of the router bit about its axis of rotation. In accordance with the present invention, this source of unbalance is compensated by providing a counterweight whose position is dependent on the angular position of the arbor within the bore. In the preferred embodiment a cam on the shaft of the arbor bears against and determines the position of the counterweight.