Patent GB-1182498-A (GB)
Title: Abrasive Tools
Inventor: MOORE ARTHUR IVAN WALTER
IPC: B24D5/06
Filed: 1967-05-16
Abstract: 1,182,498. Abrasive tools. PRODUCTION ENG. RESEARCH ASSOCIATION OF GREAT BRITAIN. 16 May, 1967, No. 22758/67. Heading B3D. [Also in Division C4] A grinding disc or wheel comprises a stiff supporting structure embodying a hub and an exchangeable cutting portion which alone embodies the abrasive material, the latter occupying only a minor proportion of the total volume of the disc or wheel, either the exchangeable cutting portion or the supporting structure being made up of a plurality of parts shaped and disposed so that the outer surfaces of the adjacent parts overlap circumferentially. A disc or wheel comprises, Figs. 1 and 2, a hub 21, suitably of steel, the rim of the hub being shaped to form a flange 23; a series of abrasive inserts are mounted on the hub. Each insert comprises a pair of lozenge-shaped abrasive members 24, consisting of bonded abrasive grains, disposed to form a chevronshaped outline and moulded into a plastics material 25 with a moulded-in tenon block 26, suitably of steel. Bolts 27 pass through holes in the flange 23 and into tapped holes 28 in the blocks 26. The head of each insert fits into the tail of the next with only small clearance resulting in circumferential overlap. The inserts may be of lozenge outline. The tenon blocks may be moulded into the bonded abrasive members, the plastics material being omitted. In a modification, Figs. 3, 4 and 5, the inserts 1 have dovetail roots fitting dovetail slots 3 in a disc 2. Coned clamping-plates 4 are secured to the disc 2 by screws 7; alternatively, spiders 6, Figs. 6 and 7, are secured to the disc 2 by screws 8. The inserts are mounted at an inclination to the axis of the disc, thus giving circumferential overlap; alternatively the inserts have a chevron form. Each insert may be of bonded abrasive grains, and may be coated on all or part of its surface other than the cutting surface or it may be carried in a housing of metal, plastics &c. Alternatively, each insert consists of a thin layer of abrasive material mounted on a stiff body, e.g. of metal. In a modification, Figs. 12, 13 and 14, a wheel has an abrasive periphery comprising a thin continuous band 13 which may have a backing of metal, plastics, cloth, paper &c. which in conjunction with a suitable bonding material may be chosen to make the band rigid or flexible. The ring 13 is gripped by the outward expansion of the rim portions of spiders 14, 15 drawn together by a nut 18. The arms of the spiders alternate and the rim portions are cut and stepped at 16 to provide circumferential overlap. The abrasive grains are held together by a bond which minimizes or avoids the initial adhesion of small particles of workpiece material to the abrasive tool and hence the build-up of loading; preferably the bond is also such that while sharp grains are retained dulled grains are released, e.g. by decomposition of the bond, at the increased local cutting temperature produced by dulled grains. The bond may be selected from the following used singly or in combination:- (i) carbonaceous material such as graphite alone or in combination with other bonds or with fillers; (ii) aluminates, phosphates, silicates, titanates, zirconates, mullite and spinel; (iii) oxides, borides, nitrides and carbides of aluminium, barium, beryllium, magnesium, manganese, titanium, silicon, zirconium. boron and thorium: (iv) phosphoric acid added to the bond raw material to produce phosphates such as aluminium phosphate; (v) propene nitrile (CH 2 : CHCN) alone or in combination with other bonding agents; (vi) refractory cements such as oxychloride cement; (vii) phenolic resins; (viii) rubbers and elastomers used alone or in combination with other bonding agents; (ix) elements or compounds used singly or in combination which can be used as a sintered bond but which have an initial softening or tacky phase development at temperature in excess of 1100‹ C.