Simplifying things a lot, the “translation” of the Jominy temprability test is a fundamental process. There is a relationship between two points in a bar of the same material where the cooling rate expressed in °C/sec is assumed to be the same. This relationship is important for comparing the cooling rate of the Jominy sample to a depth Ji, with the cooling rate of a bar with a diameter X at a depth Y. This same speed results in the same transformation structure or one % of transformed martensite equal in both samples, or the same hardness HRC. In this way we can anticipate what hardness will reach a cylinder for example 45 mm diameter tempered in oil at 70 guessingC (taking simplified H=0.4 inches  -1 for an oil of average drasticity) through the diagram of Gerber Wyss. This diagram is used to draw the curve in U (variation of hardness on the section) of a cylinder of defined diameter: on the axis of the ordinates we read the diameter of our cylinder, we trace a parallel to the ascisse until we meet the dotted line, at the cylinder surface. Here you follow the nearest continuous line and every time it crosses the dotted line (points of the U curve of our cylinder) you look for the intersection with the axis of the excise. Each point of the abscissa is the corresponding point of Jominy toughness.