PURPOSE: To provide a bolt set of which variation of the torque coefficient is small in the change of temperature, compounding ratio, grain size, depositing quantity, and the like and the torque coefficient is synthetically highly stable.

CONSTITUTION: Lubricant of which the basic agent is lubricating oil, for example, mineral oil and the mixed agent is powder of silicate hydrate rock, is spread on the surface of a high strength bolt. The silicate hydrate rock is some one among mica, talc, kaoline, bentonite. The optimum concentration of the silicate hydrate rock is about 5%(wt.), the optimum deposit quantity per unit area is about 0.0006g/cm2. In substantially applicable range, the concentration of silicate hydrate rock is about 1%(wt.)-20%(wt.), the grain size is about 1μm-100μm, the deposit quantity per unit area is about 0.0005g/cm2-0.15g/cm2. At graphing obtained data, temperature characteristic of torque coefficient of each sample bolt is shown that by conventional treatment is in the graph 1 and that by coating treatment of lubricant having 5%(wt.) concentration of silicate hydrate rock in the graph 2.