a handy air tool has a grip including a cylindrical tool holding section and a valve housing fitted therein . both tool holding section and valve housing are molded from plastic material . air supplying and exhausting passages are formed at the time of molding the valve housing and a hole for receiving a control a valve mechanism without requiring finishing . a least portion of air supplying ducts can be formed between the tool holding section and the valve housing . the tool is provided in the tool holding section with a locking mechanism comprising a hook portion extending from the free end of an operating lever toward the grip , and restricting elements for holding the hook portion so as to close a control valve member when it is necessary to keep the tool in a non - operating state . when applied to a grinding belt type air tool , a latch mechanism is provided for selectively retaining a grinding belt in a loosened state and in a tightened state and for preventing the grinding belt supporting member from slipping off a tension bar .