Abstract: A power wrench utilizing a power transfer mechanism supported in a housing, on a frame or the like by which input rotational torque can be transferred to output rotational torque having different rotational speed and torque characteristics without exerting any reaction force against the housing or frame thereby eliminating the necessity of providing an external anchoring device for the housing or frame with the device having particular utility as a wrench for rotating nuts, bolts and the like but also being capable of effective use for various power transferring functions.