Tar removing mechanism for pneumatic nailing machine

A pneumatic nailing machine for driving a nail to a work, comprising: a main unit having a body; a cylinder disposed in the body of the main unit; a nose portion being hollow and continously extending from the main unit, the nose portion having a driver guide hole; a piston slidably inserted in the cylinder; and a driver coupled to the piston in the cylinder, and being slidable between a uppermost position and a lowermost position, wherein the driver and the piston are driven by high pressure compressed air supplied into the cylinder, and the nail supplied to the nose portion is hammered by the driver, the driver including, a base portion positioned near the piston and having a relatively large diamter so as to be substantially equal to an inner diameter of the driver guide hole, wherein the base portion is fitted into the driver guide hole when the driver reaches the lowermost position, and a tip end portion has a diameter so as to be smaller than an inner diameter of the nose portion, wherein the driver is loosely guided by the driver guide hole so as to swing during hammering, and the tip end portion of the swinging driver scrapes off tar adhering to an inner wall of the nose portion.