M68×1.5安全攻丝夹头(见图),是我厂在加工上海50型轮式拖拉机前轮壳端部M68×1.5深9毫米不通孔螺纹时,试验制作的一种简易辅助工具。借助于这个安全攻丝夹头,使原来要在车床上加工的螺纹,可以用钳工攻丝代替,从而提高了生产效率,减轻了车制螺纹的紧张工作。夹头中采用了四片我厂生产的石棉混合物压制的制动片作为夹头中的摩擦元件,因此, M68 × 1.5 safety tapping chucks (see photo) is a kind of simple auxiliary tool which is made by our factory when processing the M68 × 1.5 deep 9mm non-through-hole thread at the front of the front wheel shell of the 50-type wheeled tractor in Shanghai. With this safety tapping chuck, the original thread to be machined on the lathe can be replaced with a bench-tap, resulting in increased productivity and less strain on the thread. Chuck in the use of four pieces of the factory production of asbestos mixture brake pad as friction in the chuck components, therefore,