冲床的主要旋转机件，装上连杆后，可承接连杆的上下(往复)运动变成循环(旋转)运动。是冲床床身上的一个重要的机件，其材料是由碳素结构钢或球墨铸铁制成的，有两个重要部位：主轴颈，连杆颈，（还有其他）。主轴颈被安装在床身上，连杆颈与连杆大头孔连接，连杆小头孔与冲床滑块连接，是一个典型的曲柄滑块机构。曲轴的润滑主要是指与摇臂间轴瓦的润滑和两头固定点的润滑。曲轴的旋转是冲床的动力源。也是整个机械系统的源动力。
The main rotating parts of the press can undertake the up and down (reciprocating) movement of the connecting rod to become the circular (rotary) movement after the connecting rod is installed. It is an important part of punch bed. Its material is made of carbon structural steel or nodular cast iron. It has two important parts: main journal, connecting rod journal and others. The main journal is installed on the bed, the connecting rod journal is connected with the big end hole of the connecting rod, and the small end hole of the connecting rod is connected with the slide block of the press, which is a typical crank slide block mechanism. The lubrication of the crankshaft mainly refers to the lubrication of the bearing bush between the rocker arm and the lubrication of the two fixed points. The rotation of the crankshaft is the power source of the punch. It is also the source power of the whole mechanical system.