Jaw Crusher Nip Angle

The nip angle describes the angle the stationary jaw plate and the pitman make with each other. The exact value of this angle isn't quoted or even determinable due to curvature in the jaws themselves but what is important is how wide vs. narrow it is. Wide nip angles can tend to expel material as the jaw closes as a large ball might squirt out from under a car tire. If the nip angle is narrow, not much vertical upward force is generated and more consistent crushing takes place. ■

To be pedantic:

The discussion on nip angles can relate to a class of comminution problems or safety problems or others.

Further, in comminution the nip angle can relate the actual or the necessary nip or critical capture angle.

Comminution: angle necessary to keep the subject ore particle between two opposing and moving surfaces as they are designed to apply pressure that capture and fracture the particle.

This can be applied to crushing, milling, and other forms of comminution equipment. It is the angle which the two plate surface frictions exceed the mechanical advantage of the particle geometry to expel itself. It is the point where the two comminution surface taper (nip) angles are either self locking or self releasing.

Think of a "Sharps" (sic) taper in mechanical engineering or machinists handbooks. When the surfaces are self-locking, comminution takes place and where self-releasing the particle is expelled from between the two surfaces.

Safety: dangerous angle where an article of clothing or body part can be grabbed when inserted at the nip point of one ore more adjacent and opposing moving surfaces, such as the point when an idler roll or pulley make contact with the conveyor belt. ■