GB1501198A - Devices for forming an annular recess around a central hole - Google Patents

Abstract

1501198 Annular rebating device; grinding NATIONAL RESEARCH DEVELOPMENT CORP 16 June 1976 [20 June 1975] 26361/75 Headings B3C and B3D [Also in Division B5] A device 10 for forming an annular rebate 12 around a hole 14 in material 16 such as wood, Fig. 4, and which may be hand driven through a ratchet drive 28, Fig. 1, be an attachment for a power tool 48, Fig. 5, or an integral part of a power tool (51, Fig. 6, not shown), comprises locating means, spigot 18 for engaging the hole, one or more abrading or, as shown, cutting means, blades 20, for removal of material around the hole, and a depth stop 24 for engaging the surface of the material around the rebate. The abrading means may comprise a roughened metal annular surface. One or more scribing cutters 23 cut into the material along the outer periphery of the rebate to provide a clean edge. The spigot, stop, cutting blades and scribing cutters may be replaceable or adjustable. In Fig. 5, the attachment is connectable to drill chuck 46 by means of adaptor 40. In Fig. 7, a hole saw 58 is detachably mounted inside the spigot 18 in order to cut the hole 14 itself in addition to the rebate and can include a pilot guide rod (70, Fig. 8, not shown) screwed into adaptor 40 for insertion into a pre-drilled centre guide hole, or a pilot drill for providing the centre guide hole as well. The details shown in Fig. 7 need not be restricted to the attachment. The hole and rebate can be covered by a plate 32 flush with the material surface to form a trap assembly for use in electrical installations in houses.