rough threading

例句：

1. 1.The car has a rough threading that makes it difficult to start.
   这辆车有一个粗糙的螺纹，很难启动。
2. 2. They used rough threading to hold the bolt in place.
   他们用粗糙的螺纹来固定螺栓。
3. 3.The engineers were using rough threading to reinforce the structure.
   工程师们正在使用粗糙的螺纹来加固结构。