Rotary vacuum-electric switch

A control shaft is rotatable in the axial opening in a cylindrical boss projecting forwardly from a front wall of a resinous plastic housing. The boss is received in a cylindrical opening in a panel formed with two slots for receiving mounting members projecting forwardly from the housing and having latching hooks for securing the housing on the panel. The boss and the mounting members form a triangle. The spacing between the boss and the plane of the mounting members is different from the spacing between the cylindrical opening and the plane of the slots whereby an interference fit is produced between the mounting members and the slots to obviate looseness. An anti-rotation pin on the housing is received in another opening in the panel. A key pin on the housing is received in a key opening in the panel. The key pin and the boss are located along a radial line oriented at an acute angle to the plane of the mounting members. Each of the latching hooks has a hook shoulder ramp slanting forwardly and laterally and a lateral ramp tapering forwardly from the hook shoulder ramp. At the intersection between the hook shoulder ramp and the lateral ramp, a rounded member projects rearwardly for engaging the panel and securely retaining the latching hook in the slot. The forward and lateral slanting of the hook shoulder ramps compensates for variations in the thickness of the panel and obviates looseness throughout a range of thickness.