Notice of correction. Numbers were reversed, should have been 0.877. I have a continuing problem with reversing digits. Being as how this arbor nut was on a thirty five year old Rockwell contractor's saw, I don't think the nut was metric. Everyday, it seems I see a new device to measure the height of the blade, or router bit. Then I get out my trusty height gauge, originally featured in either ShopNotes, or Woodsmith, that uses the plastic digital calipers from HF. Unfortunately, it only measures to the 100th of an inch, or the tenth of a MM. Seldom can I cut anything that close. As for a straight edge, look at John White's "Master Bars" that are made from MDF and drywall screws. Also look at how he uses a couple scraps and dial indicator to do miter slot and fence alignment. His methods are as accurate as the hundred dollar plates. As a plus, if I lose, or drop my scraps, I haven't lost a small fortune.