One more idea, there exist worm drive micrometers which allow you to step down the linear movement per revolution even more: https://www.global-optosigma.com/e

One more idea, there exist worm drive micrometers which allow you to step down the linear movement per revolution even more: https://www.global-optosigma.com/en_jp/Catalogs/pno/?from=page&pnoname=WGP&ccode=W8005&dcode= https://www.global-optosigma.com/en_jp/Catalogs/pno/?from=pa... If you have machining/fabrication skills, it might also be possible to buy a few worm gear sets and modify your micrometer to move really slowly but precisely.