BONMAC Special 4 – Jaw self centering chucks mechanism is made with the help of screws which have left hand thread on one side and right hand thread on other side. This mechanism moves two jaws simultaneously. The height of jaws is more than normal chucks. Threaded holes are provided on jaws. Upper portion of these jaws are kept soft so that machining or welding can be done. Special type of fixture can be mounted on the Jaws to suit special jobs. These chucks are not as accurate as scroll operated self centering chucks, but these can tolerate heavy load. These are generally used for YOKES manufacturing industry. Operating Key, Mounting Bolts are provided with each Chuck.