A tensioning means for a rotary handpiece is described in which the handpiece (2) is characterized in having a planar rotating blade (12) provided with a plurality of teeth and a plurality of cutting elements (22) capable of moving reciprocally in a linear direction in response to contact by the teeth of the rotary blade (12) when it rotates. There is a clearance gap between the rotary blade and the cutting chips, the size of which is varied by movement of the tensioning means so that the cutting characteristics of the handpiece are changed in accordance with movement of the tensioning means which applies tension to the rotary blade. In one form, the tensioning means comprises a rotating spindle, a flanged member, a bearing member and a resilient means such as an O-ring located between the flanged member and bearing member.