The invention starts with a range finder with a measuring device and at least one measuring limit stop body, which can be moved out of a housing and features at least one measuring limit stop in a reference plane for range finding between the reference plane and an object that is to be measured. The spin head includes a rotatable body, and chuck pins protruding upward from the body and configured to support an edge of a substrate placed at the body when the body is rotated. The two grounding boards can be fastened with each other to enclose outer edges of the first terminal block and second terminal block when the metal separating plate is assembled between the first terminal block and second terminal block, so as for allowing the assembly tongue plate to be easily and quickly assembled into the metal casing. One of the electrode plates is adhered to the side members by applying an adhesive to the side surfaces of the electrode plate and the side surfaces of the side members. The methods and apparatus may be used for handling semiconductor wafers. The present invention comprises an tapered auxiliary pole, situated below the main write pole and separated from the write pole by a lower non-magnetic gap.