Borehole Diameter Micrometer
The micrometer is a mechanical device used to measure the diameter of a roof bolt hole along its length. The standard unit has a range of 25 to 37mm and a 2.5m flexible section (connecting handle to head). A larger size unit is also available for 30-50mm boreholes.
It features three expandable arms for precise diameter measurement, is easy to use, and is robust for heavy duty work.