Abstract: An impact tool includes a brushless motor having a rotor extending in a front-rear direction and disposed in a motor housing constituted by left, right and rear motor housings. A battery pack is disposed below the motor housing in an up-down direction. A plurality of first screws extend in a left-right direction and fix the left motor housing to the right motor housing. A plurality of second screws extend in the front-rear direction and fix the rear motor housing to the left and right motor housings. A fan is disposed between the rotor and the rear motor housing, a grip housing is disposed downward of the motor housing, and a planetary gear mechanism is disposed frontward of the motor. A spindle is disposed frontward of the planetary gear mechanism, a hammer is disposed on an outer circumference of the spindle, and an anvil is disposed frontward of the hammer.

Abstract: A method of enhancing naturally developed color of an anodic oxidation coat on Al or Al alloy wherein the coat is formed by an electrolysis employing a warmed electrolyte containing at least sulfuric acid and an electric current of which the polarity is periodically reversed to be negative for a period less than 50% of each cycle while being applied to Al or Al alloy dipped in the electrolyte as anode for 20 to 40 minutes and the thus coated Al or Al alloy is subjected to a heat treatment in a boiling sealing liquid or a boiling metallic salt solution for 20 minutes. Preferably, the electrolysis is carried out for most of the electrolysis time with the current reversed for a small period of about 5% each cycle and during the terminating stage with the current reversed for a larger period of 30 to 35% each cycle. A sulfur compound is accumulated in the coat during such electrolysis and is combined with an added alloy element of the Al alloy during the heat treatment to further develop the color of the coat.