Patent ID: 8858142

Claim:
An earth bolt capable of coming into electrical contact with a member coated with an insulating film, said earth bolt having a head and a threaded body, wherein an annular ridge capable of scraping off the insulating film is formed in the bearing surface of the head so as to surround the threaded body, wherein a first annular groove capable of holding fragments of the insulating film scraped off by the annular ridge is formed in the bearing surface of the head contiguously with the outer side of the annular ridge, the threaded body is provided with protrusions protruding radially outward from the crests of turns of the screw thread and capable of scraping off a second insulating film coating the internal screw thread of a nut with which the threaded body is to be engaged and when the earth bolt is turned for tightening, the annular ridge protruding from the bearing surface of the head fractures and removes part of the insulating film coating the member and the continuous annular ridge seals a part inside the annular ridge in a watertight fashion.