A valve (11) for controlling the flow of a drilling fluid through a down-hole tool (10) positionable in a wellbore penetrating a subterranean formation. The down-hole tool has a housing with a drilling motor therein and a drill bit (1) at an end thereof. The drilling motor (9) has a housing with a rotor (206) rotationally movable in a rotor channel (204) as the drilling fluid passes through a rotor channel between the housing and the rotor. The rotor has a bypass channel therethrough for bypassing a portion of the drilling fluid therethrough. The valve includes a valve plate positionable upstream of the motor. The valve plate (200) has at least one flow passage (226) and at least one bypass passage (220) therethrough. The flow passage is in fluid communication with the rotor channel for passing the drilling fluid therethrough. The bypass passage is in selective fluid communication with the bypass channel when the rotor rotates about the housing and moves the bypass channel into alignment with at least a portion of the bypass passage for bypassing a portion of the drilling fluid therethrough whereby a hammering effect is generated on the bit.