Most of these are after marketing tools, IMHO, more for checking the alignment. Simplest way: sharpie test This should be good enough for most hobbyists. Other more "advanced" way do not guarantee you for better results. Alignment tool from Mahlkonig: - $105 It's like a check tool, rather than calibration tool. But should be adequate to do the job. For EK43: ...this alignment tool will allow you to check that your stationary burr is properly perpendicular to the drive shaft along its entire circumference Dial indicator: 0.01mm $250. If you are serious, better send your grinder to a testing lab, and get a testing report. Once after full assembly, how to make sure the whole system , ie two burrs, axle are still in perfect alignment? The grinding compartment design and tolerances is the most critical part. Such tool barely touch it. The alignment can go awfully wrong if: The dial indicator threads aren't co-centric with axle. The burr screws are not tightening burrs co-c...