When grinding the valve root arc (Fig. 1), we need a positioner that can be positioned axially and radially, and can clamp the valve for grinding. In the past, we used the ordinary spindle tip sleeve to position the 60° inner cone surface and the valve disc end chamfer. The positioning accuracy is affected by the diameter and chamfer size. For this reason, we designed a new elastic positioner (Figure 2 ), the effect is better.