Abstract: In construction of a tool holder used for boring or tapping by vibratory rotation of a tool such as a cutter, rotation is transmitted to the tool by a rotary holder in a casing and vibration is transmitted to the tool by a vibration piece eccentrically coupled to a drive shaft. An outer oil reservoir is formed between the rotary holder and the casing whereas an inner oil reservoir is formed between the rotary holder and the vibration piece. A pump unit is arranged within the first oil conduit for communicating the two oil reservoirs so as to allow flow of oil from the inner oil reservoir to the outer oil reservoir only when the vibration piece performs a composite movement. The second oil conduit is formed in the vibration piece in order introduce oil in the outer oil reservoir into a space present at the joint of the vibration piece to the drive shaft.

Abstract: A tool holder has a prime shaft which receives an external torque and is partly accommodated in and partly projects from a casing; a speed reduction unit having a coaxial three-layer structure consisting of a wave generator, a flexible spline and a circular spline being disposed in said casing, the wave generator being connected to the prime shaft in the casing, of the flexible spline and circular spline, one is secured to the casing while the other is an output section; a rotary holder secured to the output section; a tool holder mounting shaft supported by a top end of the rotary holder, the tool holder mounting shaft having a top end portion projecting from the casing; a crankshaft rotatably provided within the inner wall of the rotary holder; crank arms secured to both ends of the crankshaft, one of the crank arms being eccentrically coupled to the wave generator, the other the crank arms being eccentrically coupled to the rear end of the tool holder mounting shaft, with respective axes positioned eccentr