nip point
A point of convergence between two rolling parts, or a rolling part and a stationary part, where all or part of the human body could become trapped and injured.
nip point: where rotating parts trap flesh and bone
A nip point is the zone where two moving surfaces converge, or where a moving surface meets a fixed one, creating a crushing or pinching hazard. The classic case is the contact line between two rotating rollers, such as in a calendar stack, a wringing machine, or a four-high mill. But nip points also form between a moving belt and a fixed pulley, between a rotating shaft and a stationary guard, or between meshing gears and a frame. Any rotating machinery with parts that come close together creates at least one.
The danger is immediate and severe. A worker's hand, hair, or loose clothing drawn into a nip point experiences shear and crushing forces. In textile mills, calendar stacks run at line speeds of 500 to over 1000 feet per minute; a hand caught there suffers traumatic amputation within a fraction of a second. The force needed to stop the machinery manually is irrelevant because there is no time. A gloved hand is no real protection, as heavy leather is simply drawn in and shredded alongside the flesh.
Recognition and control
Nip points are often invisible during normal operation. A calendar looks like smooth metal surfaces coming together; the danger is not obvious to someone unfamiliar with the equipment. Guards are the primary control. Modern equipment must have fixed guards that physically prevent access, or hinged guards interlocked with emergency stops. Older machines, especially textile equipment, may have only chain guards or partial shields that do not fully block the nip. Pinch rolls and other machinery with moving conveyance surfaces require specific attention because workers often need to monitor material feeding.
The term appears across manufacturing sectors: rubber calendering, textile finishing, paper mills, metal rolling, and any process involving rotating cylinders or shafts. Regulatory agencies and standards bodies, including OSHA and ISO, identify nip points as a primary hazard class. Training often focuses on teaching workers to locate nip points on equipment they use, because many injuries occur during setup, cleaning, or troubleshooting when guards are removed or bypassed.