Lathe Milling Machine Speed Controller Potentiometer Guard

thingiverse

The Variable Speed Controller (Potentiometer) on some lathe and milling machines relies on a BLDC speed controller. A critical design flaw can cause damage to the speed controller when the potentiometer shorts to the front panel, which is grounded. A significant voltage reading of 125VAC exists between any terminal on the potentiometer and the metal front cover. The aluminum metal front cover of my milling machine has no paint on its back surface, leaving only a small gap (less than 1mm) between the potentiometer and the metal surface when installed. When in operation, vibration can cause these components to make contact with each other, resulting in a short circuit. The shield/guard on the potentiometer is designed to prevent the terminals from coming into contact with the metal front panel surface.