A shear is disclosed in a preferred form which is particularly suited for cutting and trimming hair and which includes means for varying the length of stroke of the cutting blade or blades which reciprocate generally parallel to the longitudinal axis of the handle, so that the unit can be manipulated in a manner similar to a comb or brush. The blade drive includes a transmission comprising a pair of eccentrics which are selectively phaseable to provide full range of stroke by addition and subtraction of their eccentric throws. The eccentrics are retained in their selected phase relationship by spring and frictional means which provide an overload release permitting the eccentrics to rephase to zero stroke when the imposed load overcomes the phase-retaining means. Control of the unit is effected by a rotatable and depressable button which controls the drive motor, adjusts the blade stroke by phasing of the eccentrics, and lowers the cutting blade or blades from a retracted position into a cutting position.