I would use "an element of the machine" or "a part of the machine."

A “piece of machinery” or a “piece of equipment” will usually have another technical and more descriptive name. Sometimes it’s not important. That room is full of machinery. There are four pieces of machinery included in the sale. Don’t forget the two pieces of equipment in the basement. The inventory shows three pieces of equipment. Have they been appraised? “Set” usually means separate things that are related. Each van is equipped with a set of tools capable of dealing with the most common residential plumbing problems.

Hi Ethan, I am not a teacher but the best way to describe how to use "set" is probably by example. If you want to describe a machine or 'part' of a machine, the best way, is to be clear as to what the machine is (unless obvious from context). For example you can say: A radio set A DVD set A television (TV) set These are machines made up of 'different' types of parts, better described as 'components' (or parts), together they make a whole single item! Together they become a 'radio / dvd / TV set'. Separately they are a 'set of components / parts, for a radio / tv etc). Another way to use 'set' (or part of a set) is where you have a group of items that together become a complete 'collection'. For example you can say 'a set of knives or forks' a set of postage stamps or DVD discs or films / photographs etc, anything that has a strong relationship with each other. Here you wouldn't use 'components' you use 'part(s)' e.g. "this spoon is 'part' of that set". So your understanding of how to use 'set' is good. Perhaps think of cars / vehicles / electrical items as machines where the word 'set' comes after the machine e.g. - 'tv / dvd / radio set' and other collections of items as 'a set of'...... e.g. knives / spoons.... I hope this helps you, Steve

You wouldn’t use “set.” It implies pieces that are or can be separated. To use “machine” and “piece”, you’d say “a piece of machinery.” That’s a very generic way to describe something like a printer and probably wouldn’t be used. “Machinery” usually refers to machines that produce other items.