StewMac

StewMac (Stewart‑MacDonald Manufacturing) is a leading American supplier of specialized tools, parts, and educational materials for luthiers—artisans who build, repair, and mod guitars, banjos, mandolins, and other fretted instruments. Founded: 1968 by Kix Stewart and Bill MacDonald and headquartered in Athens, Ohio, USA. They were acquired by private equity firms (Brookside Capital & Champlain Capital) in 2016.

StewMac is widely regarded as the go-to source for high-quality luthier supplies. There don't seem to be a lot of option these days. They innovate based on real-use feedback, support hobbyists and professionals.

Dan Erlewine among other professional luthiers seem to maintain and value relationships with StewMac.

Stewmac → (company website)