Abstract: Tappet is an important component in valve mechanism of automobile engine. It belongs to thin-walled parts, and it becomes deformed unavoidably in final grinding. Existing processing methods can barely guarantee its dimensional tolerance and geometric tolerance. In this paper, a new type of float film clamp is designed. This clamp adopts hard spot support in the bottom of the tappet, and adopts float support in the other side. It can realize surface grinding and internal grinding simultaneously, so can guarantee its dimensional tolerance and geometric tolerance better.