Granite is becoming a popular material for the workshop. It’s dimensionally stable and corrosion-free, and its polished, slick surface makes it ideal for machine tables, but is it a good material for precision measuring tools? Steel City seems to think so — they’re selling an angle gauge made from it.
They machine this solid black granite angle gauge to a perpendicular accuracy of .001″ and a tolerance of 0.1° over the entire length of the 45° edge. Since black granite is the densest granite, you’re not going to see much change over temperature and humidity extremes.
You can purchase this granite angle gauge with its carrying case at Woodcraft for $20.