In this video we work the lathe work on the 8620 alloy steel base for the traveling squareness comparator. This instrument allows the metrologist to inspect as many points along a surface as required to verify perpendicularity. It also allows access to small features not normally accessible by traditional surface gage comparators. The vertical guide pin will be pressed into the base after heat treat and grinding. The small rest pads on the bottom of the base will be lapped to establish permanent perpendicularity with the vertical pin.