PURPOSE: To enable sizing with large force without increasing the height of a press by using a bell crank for the upper ring of a knuckle press used for sizing in cold forging, connecting the other end thereof to the crank pin of a crank shaft and driving the same.

CONSTITUTION: A link 3 connected to one end of a slide 2 of a press 1 is connected to one arm 6 of a crank 5 fitted freely rotatably to the upper shaft 4 of the slide 2 and the other arm 7 is connected via a connecting rod 8 to the crank pin 10 of a crank shaft 9. A main gear 11 fixed to the shaft 9 meshes with a pinion 13 fixed to an intermediate shaft 12. A gear 14 fixed to the shaft 12 is meshed with a pinion 16 provided to a revolving shaft 15. A flywheel 17 supported to the shaft 15 is driven by the main motor of the press. The slide 2 is moved upward and downward at a stroke S between the bottom dead point and the top dead point shown by a dotted chain line by such device, by which sizing of a large-sized blank material is made possible.