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Class 1 gauge blocks are at the heart of your metrological traceability chain. Their integrity directly determines the validity of your calibration results and ISO 17025 compliance.
A. Handling — Mandatory Rules
Zero skin contact: The acidity of perspiration causes irreversible corrosion of measurement surfaces within a few hours.
Mandatory equipment:
- Clean cotton gloves (change after each session)
- Pliers with plastic or silicone tips
- Thermal insulating support to prevent expansion due to contact
Protection against shocks:
- Never slide the gauge blocks roughly
- Never place a gauge block on an unprotected workbench
- Always use a rubber mat or a clean surface plate
B. Cleaning — Before and After Each Use
- Degreasing: Microfiber cloth soaked in isopropyl alcohol
- Wiping: Single straight motion — never in a circle (micro-scratches)
- Drying: 5 minutes minimum in open air before any measurement
C. Storage and Preservation
Corrosion protection: If unused for more than 24 hours, apply a light film of metrological petroleum jelly.
Storage:
- Each gauge block in its dedicated slot in the original case
- Case closed in a sealed cabinet
- Temperature: 20°C ± 5°C — Humidity: < 60%
D. ISO 17025 Requirements §6.4
The auditor will systematically check:
- The presence of gloves or pliers in the metrology room
- The condition of the cases and the absence of oxidized or scratched gauge blocks
- The valid calibration certificate for the gauge block set
- Traceability of the last cleaning and last visual check
⚠️ A scratched or oxidized gauge block must be immediately removed from service and sent for verification to a COFRAC accredited laboratory. Its use invalidates all calibrations performed with it.
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