Micrometers are a common sight in many quality departments. Many organizations that use micrometers in production or inspection often keep a set a gage blocks to reference micrometer calibration. Technicians and quality personnel are sometimes unsure of the best way to care for gage block sets or if gage block and micrometer calibration should be scheduled at the same time. Below, we answer common micrometer and gage block questions.
The 5 point check is a micrometer calibration method. Measurements are verified at 5 points, other than zero, with traceable gage blocks. Quality best practices recommend to check the maximum range and take measurements at 6.25%, 12.5%, 25%, 50%, and 100%.
Wear gage blocks are used to prevent wear on other blocks in the set. They are made from a different material than typical gage blocks that provides better durability. The wear blocks are placed on the outside of gage block combinations during measurement. The idea is that they will protect the higher precision, more expensive gage blocks from damage. Wear blocks are much more economical to replace than a regular gage block. If gage blocks are frequently used or subject to damage, wear blocks are recommended.
In most cases, gage block and micrometer calibration are recommended annually. For organizations that batch calibration, this will often happen at the same time. Instruments that have increased exposure to debris or are likely to sustain damage may require a shorter calibration interval.
Yes, it is possible for gage blocks with nicks or burrs to damage the spindle or anvil of the micrometer. To ensure that a micrometer isn’t damaged by gage blocks, inspect the gage blocks before use. Do not use any gage block with noticeable nicks, burrs, or other type of damage. Gage blocks with minimal problems may be conditioned using the stoning technique.