Rotatable socket for a dental handpiece

In a rotatable socket for supporting a tool for rotation in a head housing of a dental handpiece, said socket having a bore for receiving a tool from one end, catch means for releasably retaining a tool in said bore, said catch means includes at least one catch member having a free end movable radially between a locking position engaged in the recess for retaining the tool in the bore of the socket and an unlocking position for releasing the tool, and a thumb actuated purchase disposed on the head housing, said purchase upon actuation engaging each catch member to radially move it to the unlocking position to allow removal of the tool from the socket, the improvements comprising the purchase having a pressure surface with an inclined portion of a predetermined shape and movable from a position disengaged from the free end of each catch member to a position engaging the free end of each catch member to cause radial movement to the unlocking position, a cover member having a peripheral edge, and means for rigidly securing the peripheral edge of the cover member to the head housing, said cover member having an elastically deformable portion movable through a stroke when pressure is applied to the purchase, so that upon applying pressure to the cover member, the deformable portion moves through the stroke to cause the pressure surface to engage the free end of each catch member and to move it radially to the unlocking position.