What is claimed is:
1. A manually operable nut-cracking device comprising: a frame having wall means and a mounting base; a fixed jaw member and a movable jaw member mounted to the wall means in opposed relationship to define between them a nut holding station, the movable jaw member being urged away from the fixed jaw member by biassing means; a lever arm pivotally connected by its proximal end with a first pivot shaft to an upper part of the wall means such that its distal end forms an operating handle movable between a fully inoperative position whereat the jaws are at their fullest extent away from one another and a fully operative position whereat the jaws are at their fullest extent closer to one another; a wedge shaped cam formed on the proximal end of the lever arm; wherein the pivot shaft being arranged adjacent to the movable jaw member and the cam being so shaped that when a force is applied to the handle to move the lever arm from its fully inoperative position to a partially operative position intermediate the fully inoperative and fully operative positions, a relatively greater mechanical advantage is generated between the cam and the movable jaw member than correspondingly when the lever arm is moved from its intermediate position to its fully operative position, whereat the movable jaw member terminating short of the fixed jaw member by a predetermined distance.