Saginaw Thermal Calculator Page
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:
By aligning the part’s “minimum section thickness” with its “mass,” and reading across to “time since quench,” a line operator could instantly estimate the core temperature to within ±15°F. No electronics. No batteries. Just laminated cardboard, brass rivets, and a clear plastic cursor. saginaw thermal calculator
Then a junior process engineer named Mira Kostic did something unexpected. She asked for a slide rule, a pad of graph paper, and three weeks of logged cooling curves from a dozen part geometries. Management thought she was wasting time. Dutch gave her the green light anyway. 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. No batteries
[ T_{core}(t) = T_{furnace} - \left( \frac{k \cdot t}{ (V/A)^{0.85} } \right) ]
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:
By aligning the part’s “minimum section thickness” with its “mass,” and reading across to “time since quench,” a line operator could instantly estimate the core temperature to within ±15°F. No electronics. No batteries. Just laminated cardboard, brass rivets, and a clear plastic cursor.
Then a junior process engineer named Mira Kostic did something unexpected. She asked for a slide rule, a pad of graph paper, and three weeks of logged cooling curves from a dozen part geometries. Management thought she was wasting time. Dutch gave her the green light anyway.
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.
[ T_{core}(t) = T_{furnace} - \left( \frac{k \cdot t}{ (V/A)^{0.85} } \right) ]