A lot of the projects we feature here on Hackaday engender the classic “build versus buy” argument. We’ve always been puzzled by that; if anyone can appreciate the sheer joy of making something rather than buying it, it should be our readers. But there’s something to be said for buying the stuff you can buy and concentrating your effort on the bespoke aspects of the project. It’s perhaps not as exciting, but needs must, oftentimes.

Let’s not forget there’s a third way though, which [Andy] explores with this ball nut modification project. Keen-eyed readers will recall [Andy]’s recent scratch-built ball screw build, in service of some top-secret, hush-hush project related to world domination and total subjugation of humanity. His homebrew efforts in this regard were a great lesson in how to machine a complex mechanism to work in a constrained space. Still, it left folks wondering why he’d go to all the trouble when he could have just trimmed an off-the-shelf part down to size. So, he decided to give that a try.

After securing a ball nut of the proper pitch and diameter, [Andy] looked for ways to shorten it without ruining it. Unfortunately, ball nuts are usually made of hardened steel, which tends to make the usual subtractive methods difficult. But when all else fails, you pull out the metal shop problem solver: the angle grinder. That had the benefit of shortening the nut while simultaneously annealing the steel around the cut, making it possible to face in the lathe. [Andy] put this happy accident to use twice in the build, and it’s a tip we’ll be filing away for a rainy day.

The whole modification process is presented in the video below, which includes testing the modified ball nut. It turned out pretty well, at least in terms of axial backlash. There are compromises, of course, but far fewer than we expected when the sparks started flying from that precision-machined ball nut.