Fastening method of fastening component

1. A fastening method of a fastening component, using a spindle to fasten the fastening component to a workpiece, wherein an upper end of the spindle is provided with the fastening component, a lower end of the spindle has a non-circular fitting portion, the fitting portion is configured to be fitted into a nut runner shaft, and the fastening method of the fastening component comprises:

an installation step of installing the fastening component to the upper end of the spindle;

a first pressing step of raising the nut runner shaft while reversely rotating the nut runner shaft in a rotating direction opposite to a fastening direction to press the nut runner shaft against the non-circular fitting portion;

a second pressing step of raising the nut runner shaft while reversely rotating the nut runner shaft in the rotating direction opposite to the fastening direction to press the fastening component against the workpiece; and

a fastening step of rotating the nut runner shaft forward in the fastening direction after the nut runner shaft is fitted into the fitting portion of the spindle.

2. The fastening method of the fastening component according to claim 1 , further comprising:

a third pressing step of raising the nut runner shaft again when the contact between the fastening component and the workpiece is released to press the fastening component against the workpiece after the second pressing step; and

performing the fastening step after the third pressing step.