The reversing method of the travel reversing valve: a pull rod is connected on the reversing valve core to reverse the travel reversing valve. Use the stroke stop on the workbench to push the pull rod to realize automatic reversing. When the worktable of the surface grinder moves slowly, when the reversing valve reaches the middle position, no matter whether the left and right cavities of the hydraulic cylinder are connected with pressure oil, return oil, or closed, at this time, the two cavities of the hydraulic cylinder are not pushed by hydraulic pressure, which will stop the movement of the worktable. Therefore, the reversing valve cannot reach the other end, and the so-called "dead center" appears.

The reversing method of electromagnetic directional valve is adopted: the travel switch is pushed by the travel stop to send the reversing signal, and the travel directional valve is changed into the reversing method of electromagnetic directional valve. Make the electromagnet act to push the slide valve to reverse, which can prevent the "dead center"; But it is a kind of on-off hydraulic valve, which opens or closes instantaneously according to the command, that is, it connects or cuts off the oil return channel instantaneously. Such a hydraulic reversing system will have a great impact during reversing.

Using the reversing method of Electro-hydraulic Directional Valve: the pilot valve does not change forward, and replacing the electromagnetic directional valve with Electro-hydraulic Directional Valve constitutes a new reversing method. The electro-hydraulic directional valve is composed of the solenoid spool valve of the pilot valve and the hydraulic spool valve of the main valve. Once the direction of the control oil circuit is switched, the main valve spool of the surface grinder will move to another working position according to the preset speed. When the direction of the main oil circuit changes, the worktable will reverse movement to prevent the reverse "dead point".