Vernier Height Gauge: Diagram, Parts, Least Count
This guide will list four basic types of height gauges — vernier, dial, digital, and electronic. Explaining different height gauge parts and how to avoid errors. In the conclusion, it will point out some precautions.
Manufacturing workers have numerous occasions to take measurements such as diameter, depth, width, length, and height. Workers use special precision instruments to get accurate dimensional readings, including micrometers, calipers, and height gauges.
As their name suggests, height gauges are precision measuring instruments used to verify the height of a machined workpiece for quality control purposes. These are relatively straightforward instruments in which a slider with a measuring jaw moves along a vertical beam and takes measurements perpendicular to a reference plane on the instrument's base.
Typically, a height gauge is used on a surface plate to either measure or scribe specific features from a datum plane. Those working in an inspection or layout department will frequently use a height gauge, which is indispensable in those areas.
Since there are four basic types of height gauges—vernier, dial, digital, and electronic--we'll start by looking briefly at each.
As their name suggests, height gauges are precision measuring instruments used to verify the height of a machined workpiece for quality control purposes. These are relatively straightforward instruments in which a slider with a measuring jaw moves along a vertical beam and takes measurements perpendicular to a reference plane on the instrument's base.
Typically, a height gauge is used on a surface plate to either measure or scribe specific features from a datum plane. Those working in an inspection or layout department will frequently use a height gauge, which is indispensable in those areas.
Since there are four basic types of height gauges—vernier, dial, digital, and electronic--we'll start by looking briefly at each.
Vernier Height Gauge
The vernier height gauge uses the main vertical scale and the smaller vernier scale to get a height reading. These gauges typically range from six inches to six feet and measure in inches or metrics.
Dial Height Gauge
Similar to the vernier style height gauges, a mechanical dial with a needle pointer replaces the vernier scale for easier reading. Dial height gauges are usually available only in smaller measuring ranges.
Digital Counter Height Gauges
Digital counter height gauges provide measurements on a dial display with a digital counter. The counter allows readings to tenths of an inch while the dial measures to the thousandths of an inch.
Electronic Height Gauges
Electronic height gauges offer digital displays instead of analog dials and mechanical counters. The electronic version lets the user choose the units of measure, such as inches or millimeters.
Each Height Gauge Parts Name Explained
- Base: Starting at the bottom, each height gauge sets on a finely ground and polished rectangular-shaped base. The main vertical scale, or beam, is fastened to the base.
- Main scale: Sometimes called the beam, the main scale is mounted on and perpendicular to the base. Depending on the type of height gauge, it might be engraved for measuring.
- Vernier scale (slider): Only on the vernier height gauge the vernier scale is engraved and slides up or down on the main scale.
- Measuring jaw: The measuring jaw holds the scriber when needed and moves with the slider.
- Fine adjustment screw: As the name suggests, turning the fine adjustment screw allows for minute movements of the slider.
- Fine adjustment clamp: The clamp holds the slider in place to prevent false readings.
Avoiding Height Gauge Errors
As we mentioned, some height gauges have long vertical beams to measure up to a few feet. Although the height is not a problem, if the gauge is not designed with a larger base, you will pick up errors in your readings. Some manufacturers use bases meant for a 12" height gauge and merely attach a 36" beam to them.
When the relationship of a high beam to a base is incorrect, the gauge can flex and wobble, influencing the measurement. And the longer the beam, the more error you could have in your readings, causing quality issues.
One method to mitigate the performance issue is strengthening the column to decrease the flex, but this only offers a partial solution. Any downward pressure on the measuring jaw, however slight and especially at the upper positions, can cause the gauge to tip slightly and skew the reading unless the base is broader and more extended. There will only be a significant improvement in the gauge's functioning when the ratio of the vertical beam to the base is decreased.
When the relationship of a high beam to a base is incorrect, the gauge can flex and wobble, influencing the measurement. And the longer the beam, the more error you could have in your readings, causing quality issues.
One method to mitigate the performance issue is strengthening the column to decrease the flex, but this only offers a partial solution. Any downward pressure on the measuring jaw, however slight and especially at the upper positions, can cause the gauge to tip slightly and skew the reading unless the base is broader and more extended. There will only be a significant improvement in the gauge's functioning when the ratio of the vertical beam to the base is decreased.
Height Gauge Errors
Image credit: https://www.theengineerspost.com
Image credit: https://www.theengineerspost.com
Even when the problems with the gauge's base-to-beam relationship are resolved, most height gauges work on a surface plate providing the reference for the workpiece and the gauge. Although most surface plates are kept clean and maintained, some are located on or near the shop floor, making it challenging to keep them clean. An imperceivable amount of dust or a small metal chip could distort a measurement by as much as 0.020" at the height of only ten inches.
Also, the plate's surface can affect the height gauge's performance. Seemingly slight imperfections will be magnified on higher measurements, so the relationship of the surface to the height gauge must be maintained, as well as the ratio of the base to the vertical beam.
Also, the plate's surface can affect the height gauge's performance. Seemingly slight imperfections will be magnified on higher measurements, so the relationship of the surface to the height gauge must be maintained, as well as the ratio of the base to the vertical beam.
In conclusion, Precautions When Using a
Vernier Height Gauge
Vernier Height Gauge
- Match the height gauge to your requirements by ensuring that the gauge's specifications are correct for your application.
- Check the slider for smooth movement without free play, and report any non-conformances to your supervisor.
- Stabilize the height gauge and datum surface by thoroughly cleaning the surface plate before placing the height gauge on it.
- Never use excessive force on the sliding and locking mechanisms. If you accidentally bang or drop the height gauge, have it repaired or recalibrated before using it again.
- Check the scriber for damage before using it with the height gauge.
- Thoroughly clean the height gauge with a lint-free cloth, especially the base and scriber.
- Adjust the zero line to the datum surface each time before you use the gauge.
- Avoid parallax errors by reading the scales directly from the front instead of off to the side.
- Do not store the height gauge in a high-humidity area.
- When storing the height gauge or when it needs oiling, use a lint-free cloth with a rust preventative oil and wipe each section, ensuring that the oil is spread evenly over the surfaces.
- Do not use a height gauge that has not been calibrated.
The accuracy of a height gauge depends on an operator's ability to follow the rules for its proper use. Because of that, training in its correct use will ensure those accurate measurements.
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