Highlighting this utility, Reddit user Vogel25 constructed a custom digital torque wrench powered by an Arduino-compatible Microchip ATmega328.

If you're not quite sure how a torque wrench actually does its job, the easiest way to picture it is by looking at an old-school, analog "beam style" torque wrench. Picture this: as you crank down on a bolt, the metal shaft right above the socket actually starts to flex and twist from the pressure. That bending motion makes a long indicator needle swing across a scale near the handle, showing you exactly how much muscle you're putting into it. A digital torque wrench does pretty much the exact same thing, but instead of relying on a mechanical needle, it uses high-tech electronic sensors to detect that microscopic metal flex. It then crunches those numbers and pops the exact reading right up on a digital screen.

For this DIY project, Vogel25 got creative by carving out a tiny slot right into the head of a standard wrench and embedding a set of four strain gauges inside it. The cool part is how they set it up: when you pull on the wrench, two of the sensors get squished tightly together while the other two get stretched out. To make sense of all those fluctuating, chaotic electrical signals, the sensors are wired into a neat little circuit called a Wheatstone bridge, which cleans up the data. From there, a trusty ATmega328p microcontroller—the same brain behind many Arduino boards—reads the steady signal and broadcasts the live numbers onto a crisp little OLED screen. Plus, you can even program in a target number, and a tiny built-in buzzer will beep loudly the second you hit the perfect tightness so you never over-tighten a bolt again.