Patent GB-1459918-A (GB)
Title: Apparatus and method for making
IPC: B24D18/00
Filed: 1974-06-17
Abstract: 1459918 Moulding grinding wheels NORTON CO 17 June 1974 [18 June 1973] 26731/74 Heading B5A [Also in Division B3]  An internally reinforced cup-type abrasive wheel comprises a recessed central hub portion 12 of predetermined axial thickness and having means 12a for mounting the wheel for rotation about a central axis, a side wall portion 14 of predetermined axial length and radial thickness extending generally axially from the hub portion and having a radial grinding surface 14b and an external peripheral surface 14d, and at least one internal layer of reinforcing material 16 integrally moulded within and bonded to the central hub and side wall portions and having a smoothly curved shape extending generally radially outward through the central hub portion and then generally axially and radially outward through the side wall portion to an outer peripheral edge. The hub portion 12 is provided with a central hole 12a which may have a bushing mechanically or adhesively secured therein. The hub portion has a frusto-conical shape which extends to the side wall portion 14 which may have a tapered peripheral surface 14d and a radial surface 14b. The wheel has one or more layers 16 of reinforcing material which may be cut from flexible sheet, foil or fabric of high strength such as metal, nylon, rayon, cotton, glass or combinations thereof. The layers are preferably of woven, braided or knitted open mesh glass fabric. The composition of the wheel may be of abrasive particles, such as diamond, boron nitride, alumina, alumina-zirconium, silicon carbide, garnet and mixtures thereof bonded with thermosetting resin, such as phenolic, or phenol-formaldehyde resin, urea formaldehyde resin, epoxy and combinations thereof. The wheel may be cold or hot pressed. The wheel may be used with a cylindrical outer surface or shaped to the form shown in Fig. 1. Moulding.-The wheel may be formed in a mould having a hollow cylinder 32 in which is a lower mould part 34 defining a mould cavity 34d. A central part 36 is slidable on a rod 42 which defines the bore of the wheel, the part 36 being spring urged so that its upper surface 36b is aligned with an upper surface 34b of the lower mould. An upper mould part 44 is slidable on the rod 42. In operation, a flexible support means 50, such as a closely woven cloth, a composite disc of glass cloth and paper, or other material is placed on the surfaces 34b, 36b and supports alternate layers of abrasive resin mix 18 and reinforcements 16; the layers 18 may be spread or preshaped. The upper mould part is placed on rod 42 and pressure applied so that a preliminary compression of the hub portion is effected by pressure between the upper mould part 44 and the central part 36. When the pressure of the springs is overcome, the abrasive and resin mix is forced into the lower mould cavity 34d to shape the wheel, the reinforcing layers being smoothly curved. The pressure applied may be between 1 and 4 tons/sq. in. The mould may be such that it can be heated to cure or partially cure, or alternatively, the cold pressed wheel may be removed from the mould and placed between a pair of pressure plates during curing for 15 hours at 140 C.