Electric power tool

An electric power tool comprising:

• a brushless motor;
• a controller configured to control power supply to the brushless motor, the controller including a detector configured to detect a load on the brushless motor;
• a rotary tool configured to be rotated by the brushless motor;
• a rotation speed detecting unit configured to detect a rotation speed of the brushless motor;
• and
• a main switch configured for switching between driving and stopping of the brushless motor,
• wherein the controller is configured to perform rotation control of the brushless motor in any one of multiple modes including at least a constant-speed control mode and a predetermined duty ratio control mode,
• wherein in the constant-speed control mode, the controller is configured to control the brushless motor to rotate at a constant rotation speed by a duty ratio smaller than 100%,
• wherein in the predetermined duty ratio control mode, the controller is configured to control the brushless motor to rotate by the constant duty ratio,
• wherein in the constant-speed control mode, when the load detected is equal to or larger than a first predetermined value, the controller is configured to perform switching from the constant-speed control mode to the predetermined duty ratio control mode, and
• wherein at least in a part of load range in the predetermined duty ratio control mode, the controller is configured to be able to drive the brushless motor at a speed exceeding the constant rotation speed.