POWER TOOL

PROBLEM TO BE SOLVED: To solve a problem of operability wherein a user needs to hold an electric tool to prevent the electric tool from being swung by holding a handle part with large force, since the electric tool is swung to an opposite side of a screw fastening direction by reaction when speed is changed from a high speed low torque mode to a low speed high torque mode in a variable speed gear automatically changed in speed according to external torque added to a spindle. SOLUTION: Swing moment to swing the electric tool 1 around a machine axis J is made larger than inertia moment (reaction) generated in the automatic speed change. A distance L from the machine axis J to a center G of gravity of a battery pack 5 and weight W of the battery pack 5 therefore are set to be large. When the swing moment becomes large, the electric tool 1 is made harder to be swung by the reaction according to the speed change. COPYRIGHT: (C)2010,JPO&INPIT