pit type grinding

例句：

1. 1. The machine is designed to perform pit type grinding.
   这台机器被设计用来进行坑型研磨。
2. 2. In the pit type grinding process, the material is crushed and then ground into small particles.
   在坑型研磨过程中，物料被破碎并磨成小颗粒。
3. 3. Pit type grinding is a common method for removing impurities from metals.
   坑型研磨是一种常见的从金属中去除杂质的方法。