Oldham coupling is used for the transmission between two parallel but not colinear shafts. It comprises of a pair of components which have the key slots and a connecting member which has the keys. The two key-slot components are connected to the driving and driven shafts, respectively. The connecting member is set between the two components by mating the keys on the connecting member with the key slots on the components. When the driving shaft is rotating, the connecting member will slide on the key slots back and forth. And the driven shaft is motivated with the same rotational speed as that of the driving shaft. However, since all members of the Oldham coupling are with pure sliding motion with respect to each other, this coupling has the wear problem.