How do you calculate heat treat rework rate?

Divide the number of parts reworked by the total parts heat treated, then multiply by 100. With 35 reworked out of 1,000 treated, that is 35 ÷ 1000 × 100 = 3.5%.

What is a good heat treat rework rate?

Captive and commercial heat treaters typically target 1-3% for established recipes; under 1% is excellent. The 3.5% in the example sits 1.5 points above a 2% target, so it warrants a recipe or fixturing review.

What is the difference between rework rate and scrap rate?

Rework rate counts parts that can be salvaged with a second operation (re-temper, straighten, re-harden), while scrap rate counts parts thrown away. A high rework rate still costs furnace time and risks over-processing, but it preserves material value.

Why is my gap to target negative?

A negative gap means your actual rate exceeds your target — you are doing worse than goal. The example shows -1.5 points, meaning 3.5% actual is 1.5 points above the 2% target.

What drives heat treat rework up?

Common causes are quench severity changes, uneven fixturing causing distortion, soak-time or atmosphere drift, incoming material variation, and worn thermocouples reading the furnace hot.

Should I track rework rate by part number or by furnace?

Both. Tracking by part number isolates geometry and material issues; tracking by furnace isolates equipment drift. Splitting the two is how you tell a fixture problem from a quench-tank problem.

Heat Treatment, Furnaces & Thermal Processing calculator

Heat Treat Rework Rate Calculator

Heat treat rework rate is the percentage of parts that come out of a furnace cycle needing re-treatment, re-machining, or a straightening pass before they meet spec. Metallurgists, quality engineers, and captive heat-treat supervisors track it because rework on hardened parts is expensive: you pay the energy and furnace time twice, and you risk decarb, grain growth, or distortion on the second pass. A creeping rework rate is usually the first quantitative signal that a recipe, fixture, or quench bath has drifted. This calculator turns raw scrap-and-rework counts into a clean percentage and tells you how far you sit from your internal target.

What this calculator does

Calculate rework rate for Heat Treatment, Furnaces & Thermal Processing: reworked parts as a share of total parts heat treated.
Use it to track rework rate against target in Heat Treatment, Furnaces & Thermal Processing.
It computes the share of a heat-treated batch that required rework, then subtracts your target to show whether you are above or below goal.

Formula used

Rework rate = parts reworked ÷ total parts heat treated × 100
Gap to target = target rework rate − rework rate

Inputs explained

Parts reworked after heat treat:
Total parts heat treated in the batch:
Target rework rate for the line:

How to use the result

Use it per furnace run, per shift, or per part number to monitor distortion, hardness misses, and case-depth re-runs against a process target.
It counts reworkable parts only — outright scrap, parts re-run for traceability, and parts reworked for non-thermal reasons can distort the number if you do not define 'reworked' consistently.

Current U.S. benchmarks

Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.

Common questions

How do you calculate heat treat rework rate? Divide the number of parts reworked by the total parts heat treated, then multiply by 100. With 35 reworked out of 1,000 treated, that is 35 ÷ 1000 × 100 = 3.5%.
What is a good heat treat rework rate? Captive and commercial heat treaters typically target 1-3% for established recipes; under 1% is excellent. The 3.5% in the example sits 1.5 points above a 2% target, so it warrants a recipe or fixturing review.
What is the difference between rework rate and scrap rate? Rework rate counts parts that can be salvaged with a second operation (re-temper, straighten, re-harden), while scrap rate counts parts thrown away. A high rework rate still costs furnace time and risks over-processing, but it preserves material value.
Why is my gap to target negative? A negative gap means your actual rate exceeds your target — you are doing worse than goal. The example shows -1.5 points, meaning 3.5% actual is 1.5 points above the 2% target.
What drives heat treat rework up? Common causes are quench severity changes, uneven fixturing causing distortion, soak-time or atmosphere drift, incoming material variation, and worn thermocouples reading the furnace hot.

Last reviewed 2026-05-12.