Heat Treatment, Furnaces & Thermal Processing worked example

Soak Time Calculator at 7.2% soak planning safety allowance: a worked example

This worked example runs the soak time calculator numbers for a tougher week than the baseline: 7.2% soak planning safety allowance instead of the typical 10%. Estimate required soak planning time from section thickness or load basis, soak rate, and allowance.

The inputs for this scenario

  • Section thickness at thickest point: 3 in (held at the documented default)
  • Soak rate per inch of section: 1.5 in / hr (held at the documented default)
  • Soak planning safety allowance: 7.2 % (the input this scenario stresses; the baseline uses 10)

Working through the calculation

  • The calculation starts from the formula this tool documents: Base soak hours = soak basis thickness or load units รท soak rate.
  • Required soak time works out to 2.14 hr at these inputs, and this is the headline figure for the scenario.
  • Base soak hours works out to 2 hr at these inputs.
  • Soak allowance applied works out to 7.2 % at these inputs.
  • Soak rate works out to 1.5 in / hr at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where soak planning safety allowance sits at 10% and the headline result is 2.2 hr, this scenario comes in 2.55% below the baseline at 2.14 hr.
  • Use it when building a heat-treat recipe or routing card for a new part, or when validating cycle time against the 'one hour per inch' rule of thumb before committing furnace capacity. A result at this level usually justifies acting on the stressed input before touching anything else, because every other figure in the table is downstream of it.

Results at a glance

  • Required soak time: 2.14 hr (headline result)
  • Base soak hours: 2 hr
  • Soak allowance applied: 7.2 %
  • Soak rate: 1.5 in / hr

Run it with your numbers

  • To rerun this with your own numbers, open the live Soak Time Calculator calculator, set soak planning safety allowance to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.