Russian engineer and maker Oleg Pevtsov has created a very unique bolt that can be tightened in either direction. Watch how the unique bolt is constructed using a metal lathe and handheld milling machine equipped with a carbide cutting tip in the videos below.
“The bolt is an M42 size with a 40 mm pitch, with grooves cut in both directions to allow left-handed and right-handed nuts to be threaded. The large pitch means that instead of a single continuous groove like a normal bolt, ten separate grooves need to be cut for each threading direction to cover the bolt surface. Since this was all machined on a manual lathe, a dial indicator was required to maintain accurate spacing. It took [Oleg] four painstaking attempts to get it right, but the end result looks very good. Instead of a fixed cutter, he used a trimming router mounted on a custom clamp.”
Source : Hacaday : Oleg Pevtsov