a support for a grinding wheel or other rotary element used for conditioning workpieces , has the wheel arbor supported upon vertically shiftable support members , so that the distance between the lowermost , work engaging area of the wheel can be adjusted in respect to an underlying platen . in one form , slide blocks carry rotary idlers in tangential contact with diametrically opposite areas of the wheel , to sense wear of the wheel &# 39 ; s periphery . as the wheel wears , the slide blocks gravitate to lower positions , to cause the wheel to be vertically adjusted downwardly to an extent that will maintain the distance between the bottom of the grinding wheel and the platen at a constant value . in a second form , an idler actuates an assemblage of links and levers that include the support members , to effect the downward vertical adjustment of the wheel .