The TikTok account @no1ideas5 posted a clip of just over seven seconds with the caption “Very Few Welders Know This Trick! Turning an Old Gear Into a Million Dollar Tool!” The hashtags are shorts, art, diy, foryou and tools. There is no speech and no on screen text, so everything below comes from what the frames show.

The tool stands on a steel pipe in an open workshop doorway, with a brick wall and a red motorcycle in the background. The base is a toothed sprocket welded flat onto a rusty plate. Rising from it is a bracket cut from a second sprocket in a curved C shape, and above that a vertical steel bar carries a coil spring, a round bearing and a curved lever with a long rod for a handle.

In the first second the lever is swung out of the way, and a hand brings in a short section of roller chain. The hand sets the chain on the lower sprocket, under the end of the vertical bar. The chain stays in place while the lever comes back over the top of the bearing and presses down. The clip repeats the motion, with the lever lifting and coming down while the chain sits in the same spot.

In the final seconds the hands take the chain out of the tool and hold the pieces up in front of the camera. The clip is too short and moves too fast to show the pin itself leaving the chain, so the video leaves the viewer to take the caption’s word that the machine does what a chain breaker does. It does not say what kind of chain this is or what size, and it does not show a second attempt or a closer look at the result.

What the clip builds is a variation on a tool that already exists in plain form. Park Tool, a maker of bicycle chain tools, says in its guide to chain tool pin replacement that the pin should be driven in a straight line, centered on the rivet, and that a misaligned chain can make the pin walk off the rivet and damage the pin, the shelf or the chain. That is the job a homemade fixture has to solve: holding the chain square under the pusher every time. In the clip, the sprocket under the chain and the C shaped bracket are doing that work.

Anyone who builds a press like this is also making a tool, and tools carry their own rules. The Occupational Safety and Health Administration’s booklet on hand and power tools says the greatest hazards posed by hand tools come from misuse and improper maintenance, that each tool should be examined for damage before use, and that appropriate personal protective equipment such as safety goggles and gloves must be worn. It also says to use the right tool for the job and to operate tools according to the manufacturer’s instructions, which a one off homemade press does not come with.

The clip shows a spring loaded bar and a hand lever, which means a pinch point sits right where the chain goes. In the frames the bare hands are placed on the chain under the plunger and the lever is swung with the other hand. No gloves or eye protection are visible in the frames.