Internal micrometer

Three-Point Interior Micrometers

For the correct measurement of an internal diameter in a borehole, a three-pronged internal micrometer is primarily recommended, as the three support points of the dowels or feelers allow the measuring instrument to self-centre in the borehole and take a perfect measurement. With this method we are sure that the axis of the workpiece and the axis of the micrometer become exactly coaxial. However, before measuring, a final check should be made to ensure that the sliding blocks or feeler gauges are properly seated along the entire length of the support in order to avoid any errors in the positioning of the internal micrometer.