Height Gauges

The height gauge or height scriber is a high-accuracy height measuring instrument. It is also used as a scriber and, in combination with a dial indicator, as an instrument for checking flatness and parallelism. They are usually used on surface plates (granite plates). The surface plate provides a flat surface on which we can freely move the height gauge.

Possible causes of errors

As with calipers, causes of errors include:

• Error due to the parallax effect.
• Error due to excessive force, because the height gauge does not comply with Abbe’s principle.
• Error due to thermal expansion caused by a temperature difference between the gauge and the part being measured.
• Error due to bending of the main bar that guides the scriber. This error is calculated as follows. As shown, installing a scriber or a centering dial indicator requires special attention, because as the dimension "h" increases, it leads to a larger error.

Example: When the dimension "h" is 150mm, the error is 1.5 times greater than when it is 100mm.

In the case of setting using gauge blocks, if excessive force is applied, its base may lift and not sit perfectly on the surface plate. This will cause an error. For accurate measurements, the gauge tip should just barely touch the block. In addition, the surface of the surface plate and the base of the height gauge must be cleaned very carefully of dust.

Using a height gauge

• Keep the main sliding bar clean from dust and contaminants.
• The parallelism between the scriber and the surface plate must be at least 0.01mm.
• The parallax effect, as with a standard vernier, can lead to significant error. When reading a measurement, always look perpendicularly.
• After use: Always clean off any water and oils.
• Storage: Avoid exposure to sunlight, high and low temperatures, and high humidity during storage. Protect from dust by covering the instrument with a cover or storing it in a box.