A trigger switch and lock mechanism therefore to be mounted in the handle of a drill housing for activating a motor of a drill wherein the trigger switch includes a speed control circuit carried on a circuit board. A trigger is slidably disposed in mounting brackets affixed on the circuit board. A locking member is slidably connected in one of the mounting brackets and is shiftable into contact with the trigger so as to lock the trigger in depressed position so that once the switch has been activated it will be locked in the "on" position at the selected speed setting. A spring is connected to the locking member to release the locking member from engagement with the trigger upon subsequent trigger depression to place the switch in the "off" position. The locking member and trigger have correspondingly high friction contact surfaces. The locking member may have a camming portion which coacts with the bracket to cause a wedge-lock action at the trigger contact surface which is releasable only upon subsequent trigger depression resulting in release of the locking member and deactivation switch upon the trigger load spring biasing the trigger to the "off" position.