Patent GB-677245-A (GB)
Title: Improvements in abrading and polishing processes
IPC: B24D3/00
Filed: 1949-05-13
Abstract: 677,245. Grinding and polishing. SOC. ANON. DES MANUFACTURES DES GLACES ET PRODUITS CHIMIQUES DE ST. GOBAIN, CHAUNY & CIREY. May 13, 1949 [May 13, 1948], No. 12892/49. Class 60. An abrading or polishing process for working upon the surfaces of solid bodies, especially bodies having surfaces of large dimensions, such as, for example, plates or sheets, and more particularly with a view to obtaining a fine smoothing of or a polish on sheets of glass, is characterised by the use of rubbing blocks obtained by binding together abrasive or polishing granules out of contact with each other by means of a binding material softer than these granules, and preferably non-abrasive or non-polishing, and by subjecting the binding material to the controlled action of a disintegrating agent to dissolve or chemically attack it, whereby to eliminate the superficial layer of the block which has become ineffective and to allow the subjacent layer, the grains of which are unworn, to operate in its turn. The disintegration of the binding material may be carried out during interruption of the action of the block or without interrupting the same, and in the latter case, in a continuous or discontinuous manner. For continuous disintegration throughout the abrading or polishing operation the disintegrating agent is added to the flushing and/or cooling liquid; for continuous disintegration the agent is supplied intermittently and separately. Disintegration by chemical attack is suitable when the solid to be worked is insensitive to chemical reactions, such as e.g. glass; disintegration by dissolution is suitable for bodies which are more sensitive to chemical reactions, such as e.g. metals. In one example, the bond for the abrasive granules is a cement capable of being attacked by an acid, the acid being used as disintegrating agent. In another example, the abrasive or polishing granules are bonded by metal or metal alloy, e.g. zinc may be used, disintegration being effected by hydrochloric acid or by a ferric or stannic salt in aqueous solution. Alternatively, the bond may be copper and the disintegrating agent aqueous ammonia. When a metal bond is used, the granules may be agglomerated with a powdered metal by compression and heating. In another example, the bond is a metallic alloy containing constituents of different degrees of hardness, generally crystallised, the least hard and the least abrasive being the ones most readily attacked by the chemical body used as the disintegrating agent; a carbon steel may be used which has been thermally treated so that its structure includes cementite (the harder constituent) and ferrite (the softer constituent), picric acid being used as the disintegrator, In another example, when the rubbing block is electrically conductive it is electrolytically attacked by causing a direct current to pass through the rubbing surface in such a way that the block is the anode; the current may enter either by way of the body to be worked, if it be a conductor, or by way of the working liquid. In another example, the bond is a gum, a natural resin or an artificial plastic material and the disintegrating agent is a solvent such as alcohol, acetone or petrol.