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General Notes on Use of Height Gauges 4. Error due to inclination of the main scale (column) D
1. Potential causes of error According to JIS standards, the perpendicularity of the column reference edge
Like the caliper, the error factors involved include parallax effects, error caused to the base reference surface should be better than:
by excessive measuring force due to the fact that a height gauge does not
conform to Abbe's Principle, and differential thermal expansion due to a ( )0.01 + L mm L indicates the measuring length (unit: mm)
temperature difference between the height gauge and workpiece. 1000
There are also other error factors caused by the structure of the height gauge.
In particular, the error factors related to a warped guide face and scriber This is not a very onerous specification. For example, the perpendicularity limit
installation described below should be studied before use. allowable is 0.61 mm when L is 600 mm. This is because this error factor has
a small influence and does not change the inclination of the slider, unlike a
2. Guide face (column) warping and scriber installation warped column.
Like the caliper, and as shown in the following figure, measurement errors
result when using the height gauge if the reference column, which guides the 5. Relationship between accuracy and temperature
slider, becomes warped. This error can be represented by the same calculation Height gauges are made of several materials. Note that some combinations
formula for errors caused by nonconformance to Abbe's Principle. of workpiece material, room temperature, and workpiece temperature may
affect measuring accuracy if this effect is not allowed for by performing a
f =h =ha correction calculation.
h 6. The tip of a height gauge scriber is very sharp and must be handled
carefully if personal injury is to be avoided.
l 7. Do not damage a digital height gauge scale by engraving an identification
f h number or other information on it with an electric marker pen.
l
f
a 8. Carefully handle a height gauge so as not to drop it or bump it against
h anything.
Installing the scriber (or a lever-type dial indicator) requires careful a Notes on Using the Height Gauge
consideration because it affects thhe size of any error due to a warped
reference column by increasing dimension h in the above formula. In other 1. Keep the column, which guides the slider, clean. If dust or dirt accumulates
words, if a long scriber or lever-type dial indicator is used, the measurement on it, sliding becomes difficult, leading to errors in setting and measuring.
error becomes larger.
2. When scribing, securely lock the slider in position using the clamping
Example: Effect of measuring point position arrangements provided. It is advisable to confirm the setting after clamping
When h is 150 mm, the error is 1.5 times larger than because the act of clamping on some height gauges can alter the setting
when h is 100 mm. h slightly. If this is so, allowance must be made when setting to allow for this
effect.
h
3. Parallelism between the scriber measuring face and the base reference
3. Lifting of the base from the reference surface surface should be 0.01 mm or better.
When setting the scriber height from a gauge block stack,
or from a workpiece feature, the base may lift from the Remove any dust or burrs on the mounting surface when installing the
surface plate if excessive downwards force is used on the scriber or lever-type dial indicator before measurement. Keep the scriber
slider, and this results in measurement error. For accurate and other parts securely fixed in place during measurement.
setting, move the slider slowly downwards while moving
the scriber tip to and fro over the gauge block surface (or 4. If the main scale of the height gauge can be moved, move it as required to
feature). The correct setting is when the scriber is just felt set the zero point, and securely tighten the fixing nuts.
to lightly touch as it moves over the edge of the surface.
It is also necessary to make sure that the surface plate and 5. Errors due to parallax error are not negligible. When reading a value, always
height gauge base reference surface are free of dust or look straight at the graduations.
burrs before use.
6. Handling after use: Completely wipe away any water and oil. Lightly apply a
thin coating of anti-corrosion oil and let dry before storage.
7. Notes on storage:
Avoid direct sunlight, high temperatures, low temperatures, and high
humidity during storage.
If a digital height gauge will not be used for more than three months,
remove the battery before storage.
If a protective cover is provided, use the cover during storage to prevent
dust from adhering to the column.
D-60
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