PURPOSE: To speedily vary the tightening depth by installing a releasing member for releasing the engagement between the screw member on a sleeve side and a screw in a connection part, when a sleeve is slid for the connection part.

CONSTITUTION: In order to adjust the tightening depth of a rotary tool, a sleeve 1 is moved forwardly by pushing an operating ring 2 to the front side. Therefore, the inner surface rib 21 of an operating ring 2 presses only an engagement part 32 on the rear edge side of a screw piece 3, and the screw piece 3 is turned, having a crosspiece 3 set between the hole of the sleeve 1 and the hole 12 on the rear side as fulcrum, and the screw 31 of the screw piece 3 is demounted from the male screw 51 in a connection part 5. Therefore, the sleeve 1 is advanced by pushing the operating ring 2 forwardly in this state. Through this advance, the tightening depth of the rotary tool is varied. When the position of the operating ring 2 for the sleeve 1 is returned to an original. The screw piece 3 is engaged with the connection part 5 again, and the sleeve 1 is connected with the connection part 5 through the screw piece 3 and held at this position.