When sourcing a used stone crusher, the mechanical integrity of core components is paramount. You must inspect the main shaft, eccentric bushings, and toggle plates for signs of excessive wear or structural cracks. For jaw crushers, check the swing jaw and fixed jaw plates; for cone crushers, evaluate the mantle and concave thickness. It is highly recommended to request a video of the machine running under load to check for abnormal vibrations or noise, which could indicate bearing failure or alignment issues.