there are two types of cup centers. the woodworking variety is a variation of the traditional live center. this type of cup center has a central point like a normal live center and also has a ring surrounding it. the ring supports the softer material around the center point and prevents the wood from splitting under pressure from the central point. a different variety of cup center is used for metalworking. the metalworking variety of cup center has a tapered hole rather than a conical point. it supports the part by making contact with the outside diameter of the end of the part, rather than using a center hole.