Telescopic shaft and manufacturing method thereof

Abstract

Provided is a telescopic shaft having a coated section that reduces sliding resistance, with fluctuation of the sliding resistance according to sliding position of the telescopic shaft being reduced. A female shaftB is fitted onto a male shaft in a state of interference, and by causing the male shaftA to slide back-and-forth a specified number of times in the axial direction with respect to the female shaftB while applying, for example, a load in a direction that bends the male shaftA with respect to the female shaftB, friction heat is generated between side surfacesof groovesin the female shaftB and the coated section, which heats the coated sectionand causes the coated sectionto expand along the entire length in the axial direction of teethof the male shaftA. Therefore, the coated sectionplastically deforms along the entire length in the axial direction of the teeth causing compressive strain to occur. By causing the male shaftA to slide back-and-forth with respect to the female shaftB in this state, the groovesof the female shaftB and the teethof the male shaftA are uniformly in contact along the entire length in the axial direction, and thus sliding friction becomes constant along the entire length of the sliding range.