To provide a fastening device which prevents chips and dust from falling down in a gap between a slide and an engaging part, has a third-hand function, makes up the engaging part at the lower side of the slide disposing a spring member in the inside of a pocket for a stand part, and to prevents the whole length of the device from being adversely affected by component parts required by the engaging part and the third-hand function.
This device is provided with two slides 3 and 4 movable in the inside of a main body 1 bearing a chin part, and movable in the opposite direction by means of screws and spindles 6 movable in the axial direction, a tightening means 19 combined with the center chin part 9 of the main body and an engaging part capable of being moved in the direction opposite to the chin part 9 and the slide 3 in the inside of the main body, and with a spring member 13 which is operated to the slipping direction of the slide carried by the engaging part 10, and applies force to the slide in the releasing direction by the fastening means 19. A holding screw 15 is extended in the inside of the engaging part 10, a projection 11 can be slid in the inside of a recessed part 12, the spring member 13 is pivoted by the projection 11 and a stand part 1a, the engaging part is engaged with a groove provided for the slide, and the tightening means 19 is carried by a free end part 17' directed to the chin part 9.