Abstract: An apparatus for cutting dovetail joints comprises one or more trapezoidal mortising chisels mountable on a drill press, each trapezoidal mortising chisel having a trapezoidal cross sectional shape with a particular slope or “pitch” on its non-parallel sides. The trapezoidal mortising chisels are used to cut sockets in the tail board of a dovetail joints, where the sockets have a trapezoidal shape with sloped sides. A given slope can be selected for the sides of the sockets by selecting a trapezoidal mortising chisel having the given slope. A washer is also provided which is mountable about the tilt axis of a tiltable work table of the drill press. The washer has a set of holes located at an angle about the washer on either side of a reference radius, where the angle correspond to the slopes of the non-parallel sides of the trapezoidal mortising chisels.

Abstract: Stitch-machining the walls of a cylindrical blind cavity of a workpiece, the cavity being deep and narrow with respect to the axis of the cavity, is carried out by: (a) supporting a tubular housing for axial movement throughout substantially the axial extent of the cavity interior and in close-fitting tolerance to the walls of the cavity, the tubular housing having a free end; (b) rotationally driving a spindle (10,000-40,000 rpm) in the tubular housing for conjoint axial movement with the tubular housing, the spindle extending beyond the housing end for carrying a radially adjustable cutting tool; (c) inserting the tubular housing together with the rotationally driven spindle into the cavity (at lineal speeds of 400-800 inches/minute) with a cutting tool radially positioned for rough boring of the cavity walls, while guiding and steering the tubular housing and spindle to accurately concentrically position the cutting tool with respect to the cavity axis; (d) substantially immediately upon the execution of r

Abstract: An expansion tap having a body (20) with a head (22) on one end and angularly tapered threads (26) on the other, with a bore (24) running therethrough. The body (20) has a shoulder stop (38) in the middle and a plurality of flutes (28) through the threaded portion. A capscrew (46) penetrates the bore (24) and is threadably engaged to a forcing cone (40) contiguous with the bore on the threaded end. A plurality of aligning ribs (44) engage the flutes (28), preventing rotation when the capscrew is tightened. The tap is inserted into a damaged threaded hole engaging the original threads in the middle and subsequently expanded by tightening the capscrew (46), thus straightening the tapered thread portion until the lands are parallel. Removal of the tap straightens and recuts the damaged threads.