It is an object of the invention to provide a
power tool that effectively prevents leakage of
lubricant while regulating the
internal pressure of a housing space for a driving mechanism.The object can be achieved by a representative
power tool that includes a too bit 119, a driving mechanism 113, 115, an enclosed housing space 107a which houses the driving mechanism and in which
lubricant is sealed in, and a path 151 which regulates pressure of the housing space 107a. On the path, a filter chamber 154 having a predetermined capacity, an inner passage 155c that communicates the filter chamber 154 with the housing space 107a, and an outer passage 159c that communicates the filter chamber 154 with the outside are formed. A filter 157 is disposed in the filter chamber 154 and spaced apart from a
peripheral edge of an opening of the outer passage 159c which is open to the filter chamber 154, so that a space 161 is created on the opening edge side of the filter chamber 154. A
throttle member 163, 167 is disposed in the space 161 and throttles flow of air which flows out to the outer passage 159c through the filter 157.