Mitutoyo Mechanical Bore Gages, also known as Mechanical Holtests, are precision measuring tools used to measure the diameter of holes, bores, and cylinders. These gages use a mechanical dial or Vernier scale to display the measured value.

The Mitutoyo Mechanical Holtest internal micrometer features three hardened-steel anvils evenly spaced at 120° for true alignment of the axis bore for accurate, easily repeatable measurements. Contact points are coated with Titanium Nitride (TiN)* for added durability and precision. The holtest’s ratchet stop mechanism provides a constant measuring force on the hardened-steel spindle to ensure accurate, even measurements.