<p>At the surgical tool's proximal end, there is a first means (3) to generate ultrasonic vibration in a torsional shear mode. There is also a second means (2) to generate ultrasonic vibration in a longitudinal compression mode. A wave guide (4) is operatively connected to both generating means and extending therefrom by a distance of nlambda/2 to a distal end provided with cutting and/or coagulating means. The ratio of the wavelengths of the longitudinal compression wave and the torsional shear wave, lambdac: lambdatau, is an odd number. Preferably lambdac=Nxlambdatau (where N is an odd integral number and x is an integer). Delicate shear motion of the torsional ultrasonic vibrational mode is combined with the more vigorous excitation of the longitudinal compression wave ultrasonic vibration.</p>
