23,565. Gonon, A. Nov. 20. Surfacing a n d polishing r o u g h knife blades. The blade 23 is held and pressed down by the block 14 against the flat surface of the grindstone 6 carried by the rot a t i n g vertical spindle 4. The block 14 is fixed to a rock -shaft 17 mounted on a slide 10. A weight on the end of a horizontal lever fixed to the shaft 17 urges the block 14 downwards until an abutment 19 bears against a guide 20 carried by the fixed frame 9. The abutment is carried by an arm 18 fixed to the block 14. The slide 10 is moved horizontally along the frame 9 by means of a constantly-rotating screw 13, which engages with a half-nut 11 projecting through the slide 10. The half-nut is fixed to a lever 12 by the operation of which the feed of the slide 10 can be started or stopped. As the knife blade moves radially across the grindstone from the centre outwards, the abutment 19 moves over the guide 20, so that, by suitably shaping this guide, a suitably-curved and tapering face and a suitably-shaped edge may be given to the knife. In a modification, the blade is pressed up against the under face of the grindstone, the block 14 being formed as an electromagnet to hold the blade better.