In the United Kingdom oil industry (1970s onwards) the term roughneck was specifically for the moderately skilled people who worked on the drill floor of a drilling rig, actually handling the specialised equipment for drilling, pressure control, etc. In practice, these workers ranged from unskilled to highly skilled, depending subjectively on the individual worker's aptitude and experience. By contrast, a roustabout would perform more general labour, such as loading and unloading cargo from crane baskets, and being assistants to the welder, mechanic, electrician or other skilled workers. Usage in America appears to have been similar, and the terms had spread to the rest of the world at least by the mid-1990s.
In the North American oilfields, roughneck is one of several roles in the hierarchy on an oil rig. A roughneck's duties could include anything involved with the connecting and "tripping" of pipe down the well bore, and the roughneck is the person when it comes to general work around the rig. The roughneck is part of the crew.
The crew of a land-based oil rig can be further divided into several positions:
Toolpusher: The boss of all crews on the drilling location, he usually lives on location for a few days at a time.
Driller: The head or boss of the crew. Responsible for the control of the rig's machinery during drilling operation and most other rig operations.
Derrickhand (Derrick-man): Responsible for the "mud", the water, or oil based mud; the mud pits where drilling fluids are circulated around the system, and the mud pump. Drilling mud is a mixture used in drilling oil and gas wells to lubricate the hole and keep oil and gas downhole. Also assumes the position in the derrick, usually 80 to 110 feet off the ground, while "tripping pipe". That is the process of "racking" 90 feet or 60 feet lengths of drill pipe back in the mast when pulling out of the hole and the reverse of this when running in the hole.
Motorman (Motorhand): Responsible for the maintenance of the various engines, water pumps, water lines, steam lines, boilers, and various other machinery incorporated into the rig. On a four-man drilling crew the motorman is also the chainhand.
Floorhand (Chainhand): Works the "make-up" tongs on the Driller side of the drilling floor while tripping pipe in the hole. Traditionally, pipe was tripped by throwing chain (wrapping a chain around the bottom pipe, attaching the new piece of pipe, and "throwing" the chain to make it jump to the new piece before drawing in the chain to fully attach the new pipe). Today, throwing chain is considered dangerous by OSHA and is against its regulations. Most roughnecks see it otherwise, but various safer machines are now used to trip pipe. These safer machines are almost without exception markedly slower for tripping pipe, which is probably the reason for the roughnecks' disdain.
Leadhand (Worm): Also a floorhand, usually the lowest member of the drilling crew. Works the "break-out" or lead tongs on the off-driller side of the drilling floor. The position on the off-driller side of the floor that this person works is referred to as the "worm-hole". "Worm" is often used as a derogatory term among more experienced roughnecks.
Roustabout (Leasehand): On bigger rigs and on offshore rigs a person who does most of the painting and cleaning so roughnecks can take care of other work.
Ginsel: The worm’s helper. Also derogatory insult given from roughneck to roughneck. Also called the fifth hand.