Abstract: The sharpening unit comprises two diamond grinding wheels 6,7 mounted on respective shafts 8, 9 rotatably supported by a carriage 14 movable away from and towards the cutting blade 4 of a leather splitting machine to bring the grinding wheels in contact with the blade bevel. Said shafts are housed in eccentric bushes 30, 31 rotatably engaged in said carriage and operable in angular rotation, which bushes can be fixed according to predetermined positions to give a desired mutual positioning to said diamond grinding wheels.

Abstract: An automatically and semiautomatically unjamming nail selection device, designed particularly for machines riveting footwear heel seats onto corresponding heels. The device has a nail tank or magazine coupled with a rotary chamber equipped with units designed to lift the nails and drop them onto a chute having a number of raceways which join with corresponding guides leading to a mobile combshaped selector moving to-and-fro in a perpendicular direction relative to the nail feed direction. The selector is designed to select such nails and deliver them to a distributor moving to-and-fro parallel to the selector and having feeding ducts leading to the utilization outlet. The selector is integral with an arm controlled by a first fluid dynamic actuator which determines its to-and-fro elastic motion, and the distributor is connected--through a rigid coupling--to another arm which is, in turn, shifted elastically to-and-fro by a further fluid dynamic actuator.