I came across the following question, and my first instinct was to vote to close as off-topic: https://gaming.stackexchange.com/q/92452. To be clear, this meta question deals only with case mods or other similar hardware mods. Let's call them Ben Heck mods.
I've held off on voting for the time being so that this discussion can take place. There are some other questions on meta that deal, at least tangentially, with this, that last one being the most pertinent. So to give a brief overview of the other questions:
hardware questions?: This question just deals with basically plain Jane hardware and its on-topicness. Besides saying that hardware questions are generally on-topic, there isn't much that affects this discussion.
Are questions about mods on topic?: This is a fairly old question dealing only about game mods. The stance there was that questions about game mods should be on-topic.
How should we deal with direct questions on hardware modding?: This is the big one, along with another linked question. The way those questions differ from this one is that they are dealing with the on-topicness of firmware mods, custom firmware, mod chips, etc. and not Ben Heck style mods. The legitimacy of said mods aside, it looks like the general consensus was to let them stay with caveats. As far as I'm concerned, those caveats don't apply here (namely piracy, enabling cheats, etc).
So the precedent seems to be set that this style of hardware mod question is on-topic. However, I don't think we can reasonably consider ourselves experts on operating a CNC machine. With the other areas of modding, I don't think it's unreasonable to consider ourselves (or at least some of us) as experts, but power tools is clearly not our area of expertise. For this reason, I feel this type of question should be closed as off-topic.