On the Level

摘要

The specifications for these spirit levels were as follows: 1) Finished length of glass 170mm to 178mm. 2) Curve of glass radius 990mm. 3) Length of bubble 25mm to 30mm. The spirit leels I manufactured usually started at 22mm long which I understood helped with calibration. 4) Glass diameter 9mm o.d. X 1.1mm wall thickness. 5) Glass type AR-Glass~R 91 Expansion. 6) Because the area in which they were being used was in the North West of Western Australia, the liquid inside the tube had to withstand a wide differential in temperature.