To provide a flexible flywheel using fastening bolts which can not be removed by a general tool.
A flexible flywheel 10 is composed of a wheel body 11, a flexible plate 13 adapted to be coupled to the wheel body 11, and a plurality of fastening bolts 12 for coupling the wheel body 11 and the flexible plate 13 together. Each fastening bolt 12 is composed of a shank part 31 formed therein with threads, and a head part 32 provided at one end of the shank part 31. The head part 32 has a star-like shape so that peak protrusions 35 are projected radially from 10 positions at equal pitches around the head part 32. The head part 32 has tapered surfaces 40 obtained by cutting the head part 32 from the end surface of the head part 32 to the tip ends of the peak protructions 35.
NAGANO SHUJI
SADOI TOSHIYUKI
