What Is a Height Gauge?
A height gauge is a measuring instrument used to measure the distance in the direction of height from a certain reference plane for machined parts.
Height gauges not only measure the height of the object to be measured, but can also be used for marking. The base point is the horizontal surface on which the height gauge is placed, such as on a surface plate, and the height from this reference point is measured.
When measuring, a sub-measure called a vernier is used to precisely measure the height. Height gauges also use a measuring tool called a scriber. The scriber is made of hard material and has a pointed tip, so it can be used to mark a line parallel to the surface plate on the object to be measured at a precise height.
Uses of Height Gauges
Height gauges are mainly used to check the manufacturing quality of processed metal products and in product development. For example, height gauges are used to check whether the height of a fabricated metal product is within the drawing specifications.
Height gauges can be used to measure the height from a flat surface accurately, such as a surface plate. The height can be measured in increments of 0.01 mm by using a vernier scale to read the scale. It features easy operation and precise height measurement, and can be used in a wide range of situations, from the measurement room to the lineside.
Height gauges are also made of a hard, sharp material at the tip, which can be used to scrape lines in the direction of height. It is important to perform the staking by securing the slider with a set screw firmly tightened to prevent the tip from moving.
Principle of Height Gauges
A height gauge consists of a main body base, a main scale with a scale on it, a column on which the main scale is mounted, a vernier that takes minute readings, a slider that is moved up and down for height measurement, and a scriber that serves as the measuring tool.
The height gauge is a measuring instrument that is placed on a surface plate together with the object to be measured. In measurement, the slider is lowered from the top and the bottom of the scriber is brought into contact with the object to be measured. This height is the measurement value. The reading is taken at the point where the main scale and vernier scale overlap.
For accurate measurement, it is important not to apply more measuring force than necessary to the scriber and to read the scale from the front. Also, the scriber must be parallel to the bottom of the base. If the scriber is not adequately secured, or if the flatness of the base plate or other surface is not ensured, stable measurement will not be possible.
After many years of use, the height gauge may tilt over the column due to aging or other factors. Attach a lever-type dial gauge or the like to the point where the scriber is mounted, and while holding it against the side of a straightedge or the like, move the slider part up and down to see how the value changes. If the pillar is tilted, it needs to be adjusted or repaired.
Other Information on Height Gauges
1. Error Factors of Height Gauges
Height gauge measurements can be subject to measurement error due to a variety of reasons. For example, excessive measuring force, thermal effects due to the temperature difference between the object to be measured and the measuring instrument, and parallax effects due to the angle at which the scale is read. It is particularly important to note that errors due to the structure of the measuring instrument are unavoidable.
The main sources of error arising from the structure of the measuring instrument are those arising from the bending of the column and the tilt of the scriber. Scriber inclination is unavoidable due to its measurement method and construction. Because the height gauge has a scriber extending from a slider mounted on the column, not only does the scriber tilt when it is mounted, but over time, gaps and rattles in the parts can cause the scriber to tilt.
Deflection due to the weight of the scriber and mounting parts can also cause the scriber to tilt. A certain amount of these structural errors occur even in new products. If the error is smaller than the resolution of the measuring instrument, there is little need to be concerned, but if the error becomes larger over time, caution is required.
Therefore, in addition to daily inspections, it is essential to perform periodic management such as calibration at a certified calibration laboratory.
2. Precautions for Using Height Gauges
The bottom surfaces of the main scale and base must be cleaned before and after use to prevent scratches, rust, and oil from deteriorating the sliding action. Some manufacturers and products specify the parallelism between the measuring surface of the scriber and the base bottom surface of the height gauge. Dust, chips, etc., on the surface plate during use or in storage can cause scratches or chipping on the base bottom surface, resulting in deterioration of parallelism.
Storage in locations subject to rapid temperature changes is also undesirable. Repeated expansion and contraction due to thermal effects will not only deteriorate the accuracy, but also cause deformation of the measuring instrument itself.
If the instrument is located near a window or wall with inadequate insulation, it will be subject to thermal effects from temperature differences. Even if the instrument is located indoors and not exposed to direct sunlight, it is still a good idea to be cautious.