Gage R&R Data Collection Sheet (Two Operators, Two Trials)
Before you trust an SPC chart or a capability index, you need to know whether the gauge is good enough. This sheet is the data-collection form for a two-operator, two-trial study, with live ranges and a quick repeatability estimate.
| Part # | Op A trial 1 | Op A trial 2 | Op B trial 1 | Op B trial 2 | Range A | Range B | Part mean | |
|---|---|---|---|---|---|---|---|---|
0.002 | 0.004 | 25.013 | ||||||
0.002 | 0.002 | 25.0305 | ||||||
0.003 | 0.003 | 25 | ||||||
0.002 | 0.005 | 25.0462 | ||||||
0.002 | 0.002 | 25.0215 | ||||||
0.002 | 0.004 | 25.007 |
Standard studies use 10 parts, 2 or 3 operators and 2 or 3 trials, in random order. This sheet gives a quick repeatability estimate only. Use your Gage R&R calculator or statistical software for full %GRR, reproducibility and ndc.
Tie MSA studies to inspection plans
Optional: a review of how gauge studies and calibration records can link to inspection characteristics in your ERP.
Optional. The tool and every export work without this. No spam.
How to run the study
Pick parts that span the process range, not ten identical ones. Number them out of sight of the operators. Have each operator measure every part twice in random order without seeing the earlier reading. Enter readings in the table. The sheet computes the range of each pair, the part mean, and the overall average range. Multiply Rbar by the K1 constant (0.8862 for two trials) to estimate equipment variation. Keep the unit and resolution the same as production.
- Use at least 10 parts for a formal study; the sample rows show how the sheet works
- Randomize the measurement order
- Operators must not see their earlier readings
- Record the gauge ID and calibration status with the export
Method and what the numbers mean
The average and range method estimates repeatability from the within-operator ranges and the part-to-part spread from the spread of part means. Equipment variation compared with the tolerance or the total variation shows how much the gauge consumes. Common AIAG guidance treats under 10% as acceptable, 10% to 30% as conditionally acceptable depending on the application, and over 30% as not acceptable. Reproducibility (operator to operator) needs the operator averages, which the full calculation covers.
Common mistakes
Using parts that are all nearly identical makes the gauge look worse than it is because there is no part variation to compare against. Letting operators see earlier readings biases the result. Studying a worn or uncalibrated gauge wastes time. Also check resolution: if your gauge cannot split the tolerance into at least ten steps, repeatability will look poor no matter how careful the operators are.
Frequently Asked Questions
Why use two operators and two trials?
It is the minimum design that lets you estimate both repeatability (same operator, same part) and some operator effect. More operators, parts and trials give a more reliable answer. Ten parts, three operators and three trials is a common formal design.
What is the K1 constant?
K1 converts the average range into a standard deviation estimate for repeatability. It is 0.8862 for two trials and 0.5908 for three trials. It comes from the d2 factor, so it depends on the number of trials per operator.
What is an acceptable gage R&R result?
AIAG MSA guidance treats under 10% of total variation or tolerance as acceptable, 10% to 30% as possibly acceptable based on cost and risk, and over 30% as unacceptable. Your customer or quality manual may set a stricter rule.
Is this a replacement for software?
No. It is a data-collection form with a quick repeatability check. For a complete analysis with reproducibility, interaction and number of distinct categories, use a full Gage R&R calculation or statistical software.
If you want MSA results recorded against gauges and inspection plans in your ERP, Netray can help set that up.
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