PURPOSE: To rapidly mount and remove using only two parts by forming the inner outline of an outer bush and the outer outline of an inner bush respectively in elliptic shape.

CONSTITUTION: An outer bush 4 has a cylindrical outer diameter, and an inner bush 3 has a cylindrical inner diameter. An inner diameter part 12 of the outer bush 4 and an outer diameter part 11 of the inner bush 3 are both provided with elliptic joint surfaces so sized that both bushes are fitted to each other in a certain angle position and that both bushes clamp a hub 2 on the outside and a shaft 1 on the inside in another adjacent position. When torsion is applied to both bushes, clamping generates elastic deformation acting as in the case of shrinkage fit, to the hub 2 and the shaft 1.