Abstract: A holder for an interchangeable knife blade comprising a handle, a chuck adapted to be threaded into the handle. The chuck has a bifurcated forward end defining a lengthwise slot for receiving a flat cutting blade, the bifurcated end defining a cam surface tapering outwardly toward the forward end to a major dimension. A tubular elastomeric ferrule is mounted on the chuck for longitudinal sliding movement relative to the chuck. The ferrule extends between the handle and the cam surface when the chuck is partially threaded into the bore, so that additional threading of the chuck into the bore causes the ferrule to slide forwardly over the cam surface. In this way, the forward end of the ferrule is stretched, thereby transmitting a clamping pressure against a blade which is located in the slot.