You may have experienced situations while running your air compressor where you have set the regulator to a working pressure, but it continues to rise up to the maximum pressure.  If you are having difficulties with setting the air pressure on your air compressor, there are some things you can try.

One tip is to fill the tank to the maximum pressure.  While it is at the maximum pressure, attach your pneumatic tool to the compressor and allow the air to flow through it.  Then, while it is still connected and air is flowing through it, turn down the regulator so that no pressure is running through the tool.  Adjust the pressure to the point where the pressure you want to operate the air tool at is displayed on the gauge.  Lock the regulator down so that the air line cannot continue to fill to the maximum pressure.

This is just one tip that may help if you just cannot figure out why your compressor continues to shoot back up to the maximum pressure, even though you have adjusted the regulator numerous times.  This may not work on all air compressors, but it is worth a try in order to get your air tool running at an optimal level.