external circular spline

例句：

1. 1.The external circular spline is used to connect the two pieces of metal together.
   外部圆环套接件用于将两块金属连接在一起。
2. 2. The engineer designed the external circular spline to fit perfectly into the hole.
   工程师设计了外部圆环套接件，使其完美地插入孔中。
3. 3.The external circular spline was used to prevent the two pieces of metal from moving apart.
   外部圆环套接件被用来防止两块金属分开。