Jacobs JCM6204 OB 5/16” PB Chuck With K0 Key The Jacobs Chuck Manufacturing Company maintains a global presence as a recognized leader in the design manufacture of precision tool and work holding devices for stationary equipment and portable power tools. Finding a better way through world-class innovation and world-class partnerships – that’s the driving force behind our business. It’s a tradition that began with A.I. Jacobs a century ago when he set up his first network of distributors for the toothed sleeve and keyed drill chuck. It’s a tradition we will carry forward with you.