Calibrating a vernier caliper to ISO 13385

As part of the periodic check of a machine shop’s measuring instruments, the metrology manager has to calibrate a 150 mm digital caliper to ISO 13385-1. They must check the indication errors over the whole travel and confirm the condition of the outside and inside jaws.

Calibration procedure and rules for an ISO 13385 caliper

Caliper range	Maximum permissible error MPE (ISO 13385-1)	Recommended gauge blocks
0 to 150 mm (resolution 0.01 mm)	±0.020 mm	20 mm, 50 mm, 100 mm, 150 mm
0 to 200 mm (resolution 0.01 mm)	±0.030 mm	50 mm, 100 mm, 150 mm, 200 mm
0 to 300 mm (resolution 0.02 mm)	±0.040 mm	100 mm, 200 mm, 300 mm

All values are given for the reference environmental conditions of 20 °C.

Mandatory inspection points and gauge blocks

Calibration is done at 20 °C, checking at least 5 points spread evenly over the working travel (e.g. 20, 50, 100, 130, 150 mm). Grade 1 or 2 gauge blocks are held between the jaws. To compare with micrometers, read our guide on calibrating a micrometer to ISO 3611.

Checking the inside jaws and the depth gauge

The inside jaws are checked on a certified setting ring. The depth gauge is checked on a gauge block standing on a granite surface plate.

Example: verification record for a 150 mm caliper

Digital caliper 150 mm (MPE = ±0.020 mm). Readings on gauge blocks: 20.00 mm -> 20.00 mm / 50.00 mm -> 50.01 mm / 100.00 mm -> 100.02 mm / 150.00 mm -> 150.03 mm. Verdict: at 150 mm, the error found (+0.030 mm) exceeds the MPE by 0.010 mm. The instrument is declared non-conforming and taken out of service.

Common pitfalls when calibrating calipers

The first pitfall is burrs on the metal jaws. The second is overtightening the slide locking screw. The third comes from a weak button cell, which makes the display jump. To manage your instruments, discover the CoteCote tooling page.