As the video begins, a cheerful young man in a rumpled shirt and tie lays down the challenge: “Can I make some fully automatic adamantium claws?”

It might seem an odd question to some — but not to fans of X-Men comic books and films. Soon, with rock guitars blaring, he is running around a workshop, equipped with a backpack and two homemade metal contraptions strapped to his arms. He holds up his fists to the camera, and sure enough, six sharp metal claws shoot from the tops of his hands: He is Wolverine!

This is perhaps one of the tamer scenes in a series of videos by Colin Furze, a garage inventor and do-it-yourself daredevil in Stamford, England. With more than 500,000 subscribers on YouTube, Mr. Furze, 34, has found an online following for his radical — and sometimes dangerous — backyard inventions, which include the world’s longest motorbike and a scooter that shoots fire from its back end. (That one got him arrested.)

Despite his penchant for such technical feats, Mr. Furze is no certified engineer. In fact, he did not even finish school; he dropped out at 16 to become a plumber.