Tightening device for threaded screw part

A driver for nut and bolt which comprises in combination:

• a shank with one end portion thereof fitted to a holder or a handle;
• a body having in one end part thereof an engaging socket to fit on the outer periphery of the nut or a head of the bolt, the other end portion of said shank being connected to the other end thereof;
• a narrow groove formed alongside an engaging surface of said engaging socket, and extending in the direction substantially parallel to the axis of said engaging socket;
• a small passage formed in said body, one end of which is blind within said body, and the other end of which communicates with said narrow groove;
• a plate spring having a bent portion at the rear part thereof and a tapering surface at the tip end thereof, said spring extending from the blind portion of said small passage up to the open end of said engaging socket along said narrow groove, the rear part of said spring being held in the blind portion of said small passage on its own resiliency to be exerted from said bent portion thereof, and the tip end of said spring projecting from said narrow groove of said engaging socket with its tapering surface to the outer periphery of the nut or a head of the bolt to be tightened;
• and
• a small port formed in said body in the direction substantially perpendicular to the axis of said body, one end thereof meeting the blinded position of said small passage, and the other end thereof being open at the peripheral surface of said body, said small port serving to push forward the rear end of said spring at the time of exchanging said spring.