Patent GB-673334-A (GB)
Title: Improvements in or relating to abrasive wheel
IPC: B24D7/04
Filed: 1950-09-22
Abstract: 673,334. Abrasive wheels. CARBORUNDUM CO. Sept. 22, 1950 [Dec. 29, 1949], No. 23328/50. Class 60. [Also in Group VIII] An abrasive wheel is composed of a body of abrasive-containing felted fibrous material having embedded therein at least one layer of non- abrasive fabric substantially co-extensive in area with the side face of the wheel. In making an abrasive cut-off wheel, Fig. 2, an abrasive-containing felted fibrous sheet material of the type described in. Specification .557,038 and composed of a felted cotton fibre base sheet held together by casein adhesive and containing approximately 85-90 per cent by weight of 24 grit size aluminium oxide abrasive grain is sized on one side with a thin coat of liquid phenolic resin prepared from the reaction product of 1 mole of phenol and from 1.1 to 2 moles of formaldehyde, the reaction being catalyzed by the addition of an alkaline catalyst, and the resin dried to a non-tacky condition. A number of circular discs are then punched out of the sized sheet material. One disc 6b is placed on a mould plunger; and on top of it is placed one disc-shaped sheet 7 of resin-impregnated woven fabric, such as a blue cotton drill impregnated with a phenolic condensation product resin such as that obtained from, the reaction of 1 mole of phenol with 1.5 moles of formaldehyde in the presence of a small amount of an organic primary amine catalyst. Ten discs 6 of the sized sheet material are then added, followed by one layer 7 of resin-impregnated fabric topped by a single disc 6a of sheet material. The assembly is then pressed at 4,000 pounds per square inch at 300‹ F. for 15 minutes. The abrasive contained in the felted fibrous material may be silicon carbide, diamonds, boron carbide, fused aluminium oxide, flint, corundum, emery, or rouge. The non-abrasive fabric may be any of various resin-impregnated woven fabrics typified by various stout, twilled linen or cotton fabrics known as drill or drill cloth, untwilled linen or cotton fabrics such as duck, or strong woven fabrics such as canvas. Such fabrics may be impregnated with resin prior to insertion in the mould, or the layers of abrasive-containing material adjacent the fabric reinforcing layers may be provided with sufficient resin size to impregnate the fabric during the moulding operation. A duck cloth, such as that known as 9 oz. " Spauldite " uncured resin filled fabric containing 50-60 per cent resin solids of a creoylic acid-modified phenol formaldehyde heat-hardenable resin may be used. when the abrasive is granular silicon carbide. Blue drills impregnated with approximately 50 per cent by weight of a liquid phenolic resin may be used when the abrasive is fused aluminium oxide. Other fabrics either felted or woven may be used. Various resins may be used for impregnating the fabric, such as urea formaldehyde resins, melamine formaldehyde resins, phenol furfural resins, unmodified alkyd resins of the glycerolphtholic acid type and amine-aldehyde resinmodified alkyd resins. The adhesive used for sizing the abrasive-containing materials may be melamine formaldehyde resins, urea formaldehyde resins, unsaturated polyesters such as polymerized glycol moleate or polymerized diallyl ester cross-linked with unsaturated monomers such as methyl methacrylate, styrene or diallyl phthalate and polyfunctional polyesters such as polymerized diallyl moleate or fumarate. A sheet of burlap or similar material may be placed between the mould plungers and the assembly of sheet material whereby the pattern of the burlap is impressed on the wheel faces during the pressing operation; the resulting roughness is stated to promote a greater freedom of cut especially in deep cutting operations. Specification 562,851 also is referred to.