Mira’s insight was simple but powerful: she realized that for a given alloy (SAE 8620, which Saginaw used by the ton), the cooling rate of a part depended almost entirely on its section modulus — specifically, the ratio of its volume to its surface area. She derived an empirical formula:
[ T_{core}(t) = T_{furnace} - \left( \frac{k \cdot t}{ (V/A)^{0.85} } \right) ] saginaw thermal calculator
In 1993, the plant closed. But a few original calculators survive in private collections — not just as industrial archaeology, but as proof that a sharp mind with a slide rule and a stack of data can solve a problem that computers (in 1957) couldn’t touch. If you’d like a visual schematic of the nomograph or the exact formula’s derivation, let me know. Mira’s insight was simple but powerful: she realized
Within six months, scrap rates from thermal cracking dropped 43%. Dutch had the tool laminated in greaseproof plastic and chained to every quench tank. Mira’s design was so effective that the plant manager sent copies to GM’s Hydra-matic and Detroit Diesel divisions. By 1962, over 2,000 Saginaw Thermal Calculators were in use across the Midwest. If you’d like a visual schematic of the
Mira Kostic eventually left Saginaw to teach at Lawrence Tech. But the calculator lived on. Well into the 1980s, old-timers would pull yellowed Saginaw Thermal Calculators from their toolbox lids, ignoring the new digital infrared guns. “Batteries die,” they’d say, spinning the cardboard disk. “This never does.”