Chain pipe cutters are a legitimate professional plumbing tool — they wrap around large-diameter pipe and use multiple cutter wheels in series to score and sever steel pipe that's too big for a single-wheel rotary cutter. Commercial versions from Ridgid or Reed cost hundreds of dollars, so a homemade build is a genuinely useful workshop project.

This video appears to walk through fabricating one from scratch, which means viewers get to see how the cutting wheels are spaced, how tension is applied around the pipe circumference, and how the chain links transfer that force into clean scoring action. The mechanical principle — distributing cutting load across many small wheels rather than concentrating it on one — is a nice piece of applied engineering that translates to other tool designs.

Note: the candidate pool this round was thin, with several pure timelapses, Shorts, and emoji-heavy clickbait. This pick stands out because it's a real tool with a real working principle, from a channel large enough (9.1k subs) to suggest some craft, but still small enough to fit the curation brief. Worth a look if you've ever wondered how plumbers cut cast iron drain stacks in place.