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 shaft 16B is fitted onto a male shaft in a state of interference, and by causing the male shaft 16A to slide back-and-forth a specified number of times in the axial direction with respect to the female shaft 16B while applying, for example, a load in a direction that bends the male shaft 16A with respect to the female shaft 16B, friction heat is generated between side surfaces 411 of grooves 41 in the female shaft 16B and the coated section 61, which heats the coated section 61 and causes the coated section 61 to expand along the entire length in the axial direction of teeth 51 of the male shaft 16A. Therefore, the coated section 61 plastically deforms along the entire length in the axial direction of the teeth causing compressive strain to occur.

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 shaft 16B is fitted onto a male shaft in a state of interference, and by causing the male shaft 16A to slide back-and-forth a specified number of times in the axial direction with respect to the female shaft 16B while applying, for example, a load in a direction that bends the male shaft 16A with respect to the female shaft 16B, friction heat is generated between side surfaces 411 of grooves 41 in the female shaft 16B and the coated section 61, which heats the coated section 61 and causes the coated section 61 to expand along the entire length in the axial direction of teeth 51 of the male shaft 16A. Therefore, the coated section 61 plastically deforms along the entire length in the axial direction of the teeth causing compressive strain to occur.