To read accurately easily a value of a cut depth by setting up optionally the cut depth by a method wherein the cut depth in progress of cutting operation is displayed as occasion demands, and a function in which descend of a vertically movable part is stopped midway is provided.

Vertically reciprocating motion is moved by guiding with an endless belt 71b1 hung vertically on a belt pulley 73b1. A graduation is marked peripherally on an outer peripheral surface of the endless belt 71b1 to make a display device, and a cut depth in progress of cutting operation is displayed at any time with a numerical value. Further, two pieces of belt pulleys 33b and the endless belt 34b on which the graduation is marked in a peripheral direction of the outer peripheral surface are installed adjacent to a front of two pieces of belt pulleys 73b1 and the endless belt 71b1 which are installed in a front leg column part. A stop pin 34e is planted on the endless belt 71b1, and a stopper 34f of which a lower surface abuts against the stopper pin 34e, is fitted to the endless belt 34b. Further, a rotary handle 53 is fitted, and descent of the vertically movable part is stopped midway.