A conductive resin-bonded CBN grinding wheel is dressed by means of an electrocontact discharge (ECD) method, and the effects of two discharge patterns, spark discharge and arc discharge, on the grinding wheel surface topography are investigated. It is found that the CBN grains are firmly held with the resin-bond matrix with no erosion of the nickel coating which covers the CBN grains when the open-circuit voltage in the spark discharge area or a voltage lower than 20 V is applied. An alloy steel is plunge ground and the grinding performance is compared between the ECD method and the mechanical dressing method using a GC cup-wheel. When the ECD dressing is applied in spark discharge mode, the grinding force shows the same value as that obtained from the GC cup-wheel method. However, the wheel wear is only one-half of the original value and the deterioration of surface roughness is lower than those in the case of the GC cup-wheel method. Introduction In the electrocontact discharge (ECD) dressing [1], a rotary electrode ring is plunge ground by an electro-conductive grinding wheel to which DC power is applied, and an electric discharge which occurs between an electrode swarf and the conductive bond yields local erosion and blowing-off of bond material due to the thermal energy of the electric discharge. The authors [2] have clarified through ECD dressing experiments for a metal-bonded diamond grinding wheel that the ECD method is applicable even for a very fine-grained diamond grinding wheel. However, for a conductive resin-bonded grinding wheel in which superabrasives are coated with nickel film, it has been reported [3] that the ECD method is not applicable because of the selective erosion of the nickel coating which causes an excessive dislodgement of the superabrasive grains. The purpose of this work is to find an appropriate condition for ECD dressing of the conductive resin-bonded CBN grinding wheel, and the effect of open-circuit voltage on the topography of the grinding wheel surface is investigated. The grinding performance is compared between the grinding wheel dressed by the ECD method and that dressed by a mechanical method using a GC cup-wheel, and the applicability of the ECD method to the conductive resin-bonded CBN grinding wheel is discussed. Experimental Method Figure 1 depicts a schematic of the one-pole-aided ECD dressing equipment and a photograph of an electrode. The dressing equipment is fixed on the table of a surface grinding machine so that the rotational axis of the electrode is positioned on the center-line of the grinding wheel width, and the dressing proceeds with the plunge grinding of the rotary electrode with a feed rate f. The electrode consists of triple rings. An electrode ring which governs the electrodischarge is arranged in the middle, and two vitrified-bonded GC abrasive rings enclose the inside and the outside Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 327-332 doi:10.4028/www.scientific.net/KEM.238-239.327 © 2003 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,21:50:20) Table 1 Dressing conditions B:Conductive resin-bonded GC ring 20mm A:Vitrified-bonded GC ring Grinding wheel Rotary electrode Graphite