External Micrometer Calibration

This standard covers external micrometers from 0 – 24″/0 – 600mm including micrometers with interchangeable anvils and also setting standards for micrometers. The manufacturing specifications and associate accuracy requirements of this standard are complex and it may be uneconomical for any company or institution to invest in equipment to the level required in order to calibrate micrometers fully in accordance with the standard.

It is highly recommended that an appropriate authority such as a UKAS approved laboratory carries out a full calibration on micrometers at least once a year. In between UKAS calibrations at a frequency based on usage micrometers should be calibrated in-house. A typical in-house calibration would include a written procedure and an associated calibration record sheet which would contain as a minimum the following listed information:

(a) Serial number

(b) Location

(c) Procedure number

(d) The flatness of anvils of new micrometers

(e) The flatness of anvils of used micrometers

(f) The linearity of the micrometer screw

(g) Results

(h) Measurement uncertainty

(i) Sentence if appropriate

(j) Date and calibrators signature

(k) Traceability to National Standards

It is necessary that any person carrying out such calibration work should have received appropriate training and have shown the ability to be confident via a suitable training authority. Training records should be held and maintained.

On the following page is a layout for a typical in-house calibration for a 0 – 25mm micrometer.

Calibration to be carried out in accordance with in-house procedure number …………………..

Serial Number: Make:

Calibration Date: Range:

The micrometer was mechanically and visually inspected for performance, damage, wear and missing parts and the

following faults were noted:

MEASUREMENT UNCERTAINTY +/- 0.002mm (between any 2 points)

Calibrators Signature: …………………………………. Sentence: ………………………………

Report:

A traceability statement in this section would be required for all items and their relevant certification utilised for the calibration of the micrometer.