Primary Crusher Selection & Design - 911 MetallurgistMar 17, 2017 . For crushing operations under 500 TPH, the design engineer will typically select a jaw crusher as they are of lower cost. In under-ground crushing plants where the diameter of the mine-shaft a skip forces limits on rock size, a jaw crusher will be the machine of choice. Again, if crushing on surface, both.primary jaw crusher design,how a jaw crusher works and what it is used forThe size of a jaw crusher is designated by the rectangular or square opening at the top of the jaws (feed opening). For instance, a 24 x 36 jaw crusher has a opening of 24" by 36", a 56 x 56 jaw crusher has a opening of 56" square. Primary jaw crushers are typically of the square opening design, and secondary jaw crushers.