(5) Grinding wheel electrodes for electrolytic grinding

The grinding wheel electrodes for electrolytic grinding are made of non-conductive abrasive particles bound by conductive binder material. Diamonds are typically used for the abrasive particles for processing cemented carbides and other steel alloys with hardness of HRC65 or more. The particle sizes seem to be in a range from 100~120 mesh. The conductive binders are copper alloys and bronze impregnated resins. For general purpose steel materials, corundum particles for the abrasives, and bronze alloys (for metal bound wheels) / copper impregnated resins (for resin bound wheels) are frequently used. The corundum particles are of 60~80 mesh for metal bound, and 100 mesh for the resin bound wheels.

When the abrasive particles wear and protrusion amount is reduced by grinding use, they need to be dressed. The metal bound wheels can be dressed by reverse electrolysis. By connecting the wheel as the anode, the work piece as the cathode, and applying a low voltage DC to dissolve the metal of the binder surface, the abrasive particles can be exposed on the surface again. The resin bound wheels can be easily dressed mechanically so the reverse electrolysis is not required.

Other than the general purpose wheel types mentioned above, there is a type called Single Layer Diamond Wheel. The wheel is composed of a metal base, (mainly copper) with a layer of diamond abrasive particles bound to the surface by nickel plating. This type offers higher performances in comparison to the general purpose wheels since the diamond abrasives protrude from the bound surface very uniformly. It is suitable for use as profile forming grinding wheels since the metal wheel base can be made into final shapes required very easily.

However, the use of this type is limited to some special cases only since it is difficult to correct/repair when the diamond particles fall off from the surface, and the costs compared between the two, one with just a single layer of diamonds versus the one with a 1~2mm layer of diamonds, shows little difference. Important characteristic required for profile forming grinding wheels is the shape formability. For this reason, graphite bonding material is frequently used. Graphite bonded corundum wheels are in use for profile forming of high speed steel. This type includes alumina, WA, C, GC grits bound by graphite with a small amount of clay.