Patent GB-1163811-A (GB)
Title: Method of Forming a Grinding Member
Inventor: HALLEWELL RAYMOND THOMAS
IPC: B24D3/00
Filed: 1967-01-04
Abstract: 1,163,811. Abrasive tools. TOOLMASTERS Ltd. 4 Jan., 1968 [4 Jan., 1967], No. 587/67. Addition to 1,044,784. Heading B3D. [Also in Division C4] A method of making a grinding member having a profiled grinding surface comprises forming a body of a kneadable composition comprising a hardenable synthetic resin having a filler dispersed therethrough, and, whilst the composition is still in a plastic state, applying an abrasive to an exposed surface of the body and simultaneously rolling the said surface with a master roller, so as to impregnate the said surface with the abrasive and form it to a predetermined profile, the profiled body thereafter being hardened with substantially no volume change. To produce a grinding wheel the composition is applied as a peripheral layer around the rim of a disc; the rim may be pre-formed to the required profile before the application of the composition but is preferably flat and roughened, as by scoring or pitting, to provide a key for the composition. The disc and its peripheral layer may be mounted and trued up and then profiled and impregnated with abrasive in situ. The abrasive and filler are normally different, but the abrasive may in some cases also be the filler or dispersed through the composition with a different filler. The composition may be wholly or partially filled with coarse grain abrasive, finer abrasive being applied superficially, so that initially when the wheel form is most accurate the wheel can be used for finish grinding; subsequently it is used for coarse grinding. The applied abrasive may be diamond of 80-200 grit size. It may be sprinkled on to the surface of the composition but is preferably sprayed on, e.g. in an air jet. In the making of a grinding wheel, a spray head may be mounted in place of the forming tool on a wheel forming apparatus such as that shown in Specification 573,877, whereby the jet is kept at a constant distance from the wheel. The resin and hardening agent used in the composition are preferably so selected that the composition retains its workable consistency for an extended period, e.g. for an hour or more. To obtain optimum workable consistency it may be necessary to include a thickening agent such as silica. Polymerizable epoxy or polyester resins, in admixture with a hardening agent, e.g. one comprising a polyamide and a mild base such as an amine, may be used. Acrylic resins with hardening agents may also be used. Any one or more of a wide variety of fillers may be used according to the properties required of the product, e.g. (a) For a soft wearing bond, suitable for fine work and for fast stock removal without damage to work: soft metals such as copper or aluminium or soft non-metals such as wood flour, chalk powder, marble flour. (b) For a hard wearing bond, giving minimum wheel wear: slate powder, silica flour or hard metal such as steel. (c) For a very hard, abrasive-wear resisting bond, giving minimum wheel wear: aluminium oxide, silicon carbide. (d) For shock resistance, where high resilience is required in hard working wheels: nylon, asbestos powder. (e) For electrical conductivity, for use in electrolytic grinding: electrically conductive metals such as copper and aluminium; electrically conductive non- metals such as graphite; non-metals and plastics coated with electrically conductive metal. (f) For thermal conductivity, giving minimum damage to work through local overheating during grinding: thermally conductive metals such as copper and aluminium. (g) For heat-resistant bond, giving minimum damage to wheel due to local overheating during grinding: heat resistant materials such as mica or asbestos powder. Where a combination of properties is required a mixture of different fillers may be used. Where a comminuted metal or mixture of metals is used alone as filler, the metallic component normally constitutes a major proportion by weight of the composition, but where a mixture of metal with another filler (e.g. an abrasive such as diamond, alumina or silicon carbide or a filler imparting shock or heat resistance) is used, the metallic component may constitute only a minor proportion by weight of the composition. There may be 60% by volume of filler and 40% by volume of resin where no abrasive is included or 60% by volume of resinous component and 40% by volume of filler where abrasive is present.