Contractors rigged a creative wiring solution for their floor sander during our county fire inspection. Fire marshal was not pleased.

There are very specific reasons to have a properly designed and rated plug on your device, and to make sure all connections are firmly made into the proper receptacle.

Right now, these fine people have their sander's hot and neutral (not quite sure why the neutral is connected to the breaker and not the neutral leg, someone else can probably enlighten) wired directly into a 50 amp breaker, and have the grounding wire fished through a screw hole in the circuit board. This presents the following problems:

First, there is no guarantee that 50 amp is the proper rating for the device. The purpose of circuit breakers is to stop the flow of electricity when a device on the circuit draws more current than is safe to do so. Maximum safe current is determined by the wire, receptacles, and devices used on the circuit. For example, the standard 50 amp electric stove circuit uses big, beefy low gauge wire, big, beefy electrical outlets, and the stove itself is designed and wired to cope with 50 amps of energy. A 15 amp circuit will use thinner, #14 gauge wire, 15 Amp rated receptacles, and any devices plugged into it will be meant to handle a maximum of 15 amps. Now, say that your power floor sander gets lodged underneath a low overhang, such as the bottom of a kitchen cabinet? It's going to be pressed very hard against the floor, and not be able to turn. The motor is going to try very, very hard to turn the sander, and is going to draw as much current as it can get to do so. In a properly rated circuit, the circuit breaker is going to say "Woah, hey! Too much power!" and shut off the circuit, forcing the sander to turn off due to a lack of power. With the sander wired to a 50 amp breaker, it's going to need to draw over 50 amps to trip the breaker - possibly way over what the sander and its cord is meant to handle - the internal circuitry in the sander, and is the cord, is going to get very, very hot before the circuit breaker trips, and may start a fire. This is why it's important to have the sander wired to a wall plug that is appropriate for the sander, and have it plugged into the appropriate outlet - everything's rating must match properly in electricity. As an aside, it may very well be that the sander is rated at 50 amps and this isn't the bad part.

Additionally, the ground (green) is really poorly secured to the circuit panel. It could fall loose from the panel at any time, especially with a device that vibrates as much as a sander. If something goes wrong inside the sander, such as the internal wiring contacting the metal case, the metal case is going to become electrically charged. If a person contacts the electrified case while it is ungrounded, they will become the ground, and the electricity will travel through them to the earth, rather than through the wiring like it is supposed to do. If the grounding wire was properly installed, the electricity wouldn't shock them (or wouldn't shock them nearly as badly).

Fwiw I am a layman who just reads about electrical work in my spare time because it interests me, so I probably missed something in the above.

/r/OSHA Thread Link -