Jacobs Medium Duty Industrial Chuck Jacobs drill chucks for industrial use (medium duty), available with threaded mounts for professional portable drilling machines and with taper fittings for stationary drilling machines. Jacobs medium duty industrial chucks feature automatic fitting for efficient, fast change of tools and self-tightening mechanism automatically increases the grip in proportion to the increase in torque during drilling. Jacobs medium duty industrial chucks fit tools of up to 20mm in diameter and machine fitting via DIN0238 of Jacobs tapers and UNF thread fittings.