A load meter is a great accessory for machinery to get a sense of how near capacity a task is bringing the machine. Here a load meter is built for a CNC milling machine using a ammeter and a voltmeter. This approach measures apparent power instead of actual power so there is some error. While not perfect, it provides the feedback necessary to know if the machine is being overtaxed and if the machine has some reserve left in it.
The video describes the theory of the meter, using Fusion360 to design the panel, and the meters construction and use.
Reference material: Determining Electric Motor Load and Efficiency
An updated version uses power meters.