What Really Drives The Interval
- Usage intensity: daily vs. occasional, single shift vs. 24/7
- Environment: coolant, chips, temperature swings, shopfloor handling
- Criticality: final inspection, safety parts, OEM programs
- Historical drift: how often has this instrument needed correction?
- Design and robustness: sealed digital caliper vs. old dial indicator
Practical Starting Points (Adjust After 1 Year)
- Calipers (digital/vernier): 12 months for normal use; 6–9 months for final inspection or harsh environments.
- Micrometers: 12 months; shorten to 6 months if used for tight tolerances or on multiple shifts.
- Dial indicators / test indicators: 12 months; 6–9 months if exposed to shock or fixtures.
- Height gauges: 12 months; check more often if moved between areas.
- Gauge blocks: 24 months for protected lab sets; 12 months for shop-used sets.
- Plug/ring/cylindrical gauges: 12–24 months depending on wear; inspect visually between cycles.
Treat these as starting values. After the first cycle, adjust intervals using your own drift and non-conformity history.
When To Shorten (Or Extend)
Shorten if you see: frequent shocks, corrosion, repeated OOT (out-of-tolerance), or customer complaints. Extend cautiously if: three cycles show minimal drift, the instrument is lab-kept, and the measurement risk is low.
Keep It Simple (And Auditable)
- One master list with due dates and owners
- Batch instruments by area/line to reduce downtime
- On-site calibration for 50–300+ handheld tools
- Store certificates with the instrument ID and next due date
A risk-based plan minimises cost and surprises. You calibrate what matters, when it matters—and have the evidence to prove it.