I'd like to ask how a variable speed drill press, lathe, etc. works. Is this on topic?
- How does a SawStop work?
- What kind of motion does a random orbital sander have?
- How does a cyclone separate sawdust?
I guess it depends on what you mean by, "How does X work?" Without further clarification, the general question is too broad. However, I think the more specific examples you listed are all good questions. In terms of "how a variable speed drill press, lathe, etc., works" be sure to clarify whether you're asking how the variable speed control works or whether you're asking about some other aspect of the tool.
I'd say that questions which are related to the actual woodworking aspect or are concerned with the general use/operation of woodworking-specific tools should be allowed.
Examples would be "How does a planer-thicknesser remove material?" or "How does the variable speed control work on a belt sander?".
I think that these are OK as they have a direct relationship to working the wood or are for tools which are absolutely specific to the woodworking industry.
If you were asking about how the gearing inside a thicknesser works or something like that, then it's more of an engineering question. I'd say the same about your "how does a cyclone separate sawdust" example because this isn't actually specific to woodworking and applies to all kinds of dust removal (such as plastics) and also cyclone vacuum cleaners.
Overall, I think there's a fine line. When it's about tools that are absolutely specific to woodworking, such as a power-planer or edge-bander, and it's not so much about the mechanical inner workings, then you're only going to be likely to get an answer from a woodworker.