GB1486802A - Cutting master and method of making a cutting master for abrasion machining - Google Patents

Abstract

1486802 Abrading tools T J O'CONNOR 13 Sept 1974 [14 Sept 1973] 40046/74 Heading B3D For an abrasion machining operation in which, e.g. a carbon electrode of a required form is produced by engagement with a cutting master having a complementary form, a female cutting master 10 is produced by providing an abrasive surface 14 on a body 15 of rigid material which surface is complementary to the required form but different in size therefrom in two mutually perpendicular directions by a predetermined amount related to an orbital movement caused between the cutting master and workpiece during the machining operation, which thereby requires a flat portion 30 on the abrasive surface. The master has means 40 to enable it to be attached to a feed means, and a manifold 48 for supplying a flushing gas or liquid, e.g. kerosene, water, air, or vacuum. Various methods are described for producing the cutting master 10. In Figs. 3-6 (not shown) a model (60) of shape required is used in an electric discharge machining operation to form a recess (52) in a steel block (54). The recess is formed oversize by an orbiting motion between the model (60) and block (54) during machining, e.g. oversize in dimensions 22, 24 but the correct size in dimension 26. The block (54) is then used as a cutting master to produce a new electrode (64). In the electric discharge machining operation, if the model (60) or cutting master is not electrically conductive, it may be spray coated with aluminium or copper. In Figs. 7-9 (not shown) a female cutting master is produced by casting a settable material (86), having abrasive particles dispersed therein, over an oversize model (90). The settable material may be an epoxy resin with sand filler. The abrasive material may be emery, carbide chips, glass, industrial diamonds. In Figs. 10-12 (not shown) a cutting master is formed by a plurality of small diameter rods (96) with sharp ends which are allowed to engage around the shape of a model (106) and are then fixed in position by a settable filler, e.g. lead, babbitt, epoxy plastics, tin, zinc. In Figs. 13-18 (not shown) model (112) has cast over it an aluminium model, which is then used to cast an electrode model (120), e.g. of copper. This copper model is used in electrical discharge machining to produce, with orbiting motion, an oversize female model (122). This model is used to cast an oversize male model (126) and an oversize female cutting master (130) is cast over the model (126). In Figs. 19-22 (not shown) a model (136) of the required shape is plunged into a settable material (140) at the same time as it is given orbital movement to produce the cutting master (146).