| 摘要 |
A drill motor control for periodically varying the rotational speed of a drill to increase the cutting efficiency of the drill bit is disclosed. The speed of the drill is made to vary according to a predetermined cycle such that the drill bit is permitted to bite into the material being drilled at lower speeds, and then the speed is increased to a point where maximum cutting efficiency is achieved. The drill motor control may either be a stand alone apparatus into which a conventional drill is plugged or alternatively may be incorporated into the drill itself. A closed loop control system which senses drill motor current may be utilized to cause the drill motor to slow down as current to the motor decreases when the drill bit ceases its cutting action such as when glazing occurs or when the drill bit has cut completely through the material being drilled. The drill motor control is also useful when the drill is being used as an electric screwdriver.
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