Abstract: A first part formed of a first material is positioned to a second part formed of a second material, which is different from the first material in degree of modification due to environmental variation, by contacting surfaces of the first and second parts. At least three projections are formed on the contact surface of the first part along a circle whose center is coincident with a reference point. Grooves are formed on the contact surface of the second part so that the respective projections are fitted therein and that have wall surfaces to which the projections can contact at the inner and outer sides of the projections. The width of the grooves is determined so that the projections contact the inner or outer wall surface of the grooves even when the first and second parts deform in different degrees due to environmental variation.

Abstract: A first part formed of a first material is positioned to a second part formed of a second material, which is different from the first material in degree of modification due to environmental variation, by contacting surfaces of the first and second parts. At least three projections are formed on the contact surface of the first part along a circle whose center is coincident with a reference point. Grooves are formed on the contact surface of the second part so that the respective projections are fitted therein and that have wall surfaces to which the projections can contact at the inner and outer sides of the projections. The width of the grooves is determined so that the projections contact the inner or outer wall surface of the grooves even when the first and second parts deform in different degrees due to environmental variation.

Abstract: A multi-phase outer-type permanent magnet stepping motor including a rotor constituted by a cylindrical permanent magnet assembly in which N (north) and S (south) poles are magnetized alternately on an inner circumferential surface of the rotor. Stator cores respectively having pole teeth are disposed in opposition to the N or S poles of the rotor through a predetermined gap. Further, excitation coils are wound in the stator cores for magnetizing the stator cores to thereby rotate the rotor such that, when a number of the stator cores is 3 and the magnetization pitch of the permanent magnet assembly is P, pole teeth of the stator cores are arranged so that the pole teeth of one stator core is shifted by an angle of 2P/3 from the pole teeth of an adjacent stator core.