Is the midpoint the average casting weight?

No. It is the midpoint of the two extremes. The sample mean requires all the individual readings.

Does a small range prove the weights are correct?

No. All readings can be close together but far from nominal. Review the endpoint deviation and individual specifications.

Use caution. Larger samples have more opportunity to include extreme values, so range alone is not a fair capability comparison.

Use the agreed sample-review criterion for this job. The calculator supplies no universal casting tolerance.

Foundry & Forging calculator

Compare the measured casting weight range with nominal weight and your allowed spread.

Compare the measured casting weight range with nominal weight and your allowed spread.

Measured weight range = highest measured weight − lowest measured weight
Relative range = measured weight range ÷ nominal weight × 100
Midrange deviation = (highest weight + lowest weight) ÷ 2 − nominal weight
Spread headroom = maximum allowed spread − measured weight range
Largest endpoint deviation = max(|highest weight − nominal weight|, |lowest weight − nominal weight|)

Highest Measured Casting Weight: Largest accepted reading in the selected weight sample.
Lowest Measured Casting Weight: Smallest accepted reading in the same weight sample.
Nominal Casting Weight: Reference mass from the drawing or approved process standard.
Maximum Allowed Weight Spread: Allowed high-to-low spread for this sample review.

Best suited to a lower maximum weight narrows the Spread, a higher maximum weight exceeds the spread limit.
Range depends on sample size and does not estimate process capability or standard deviation. A spread limit does not replace individual casting weight specifications.

The producer price index for steel mill products stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 3,569 primary metal manufacturing establishments employing about 354,911 workers (Census County Business Patterns, 2023).

Is the midpoint the average casting weight? No. It is the midpoint of the two extremes. The sample mean requires all the individual readings.
Does a small range prove the weights are correct? No. All readings can be close together but far from nominal. Review the endpoint deviation and individual specifications.
Can I compare samples of different sizes? Use caution. Larger samples have more opportunity to include extreme values, so range alone is not a fair capability comparison.
Where does the allowed spread come from? Use the agreed sample-review criterion for this job. The calculator supplies no universal casting tolerance.

Last reviewed 2026-10-06.