How to Measure Parallelism
Define the surface for testing., Define the datum., Ensure that the datum is level and clean., Define the tolerance range., Ensure a consistent temperature.
Step-by-Step Guide
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Step 1: Define the surface for testing.
Parallelism is a quality that can be tested on several different types of surfaces.
These are labeled based on their positions relative to each other.
You may wish to test parallelism of the following:
Planar surface:
Opposite flat surfaces of a rectangular solid need to be parallel to each other.
Cylindrical surface:
A cylinder appears round when looking at its end, but when held upright, its sides must be parallel for the cylinder to function properly.
Parallelism also needs to be measured on the interior cylindrical surfaces of drilled holes. -
Step 2: Define the datum.
The datum is a flat surface that you use as a reference.
This will be one edge or corner of the object being tested.
Measurements for the size and shape of the object are then drawn in reference to the datum.In technical drawing, the datum is marked with a capital letter in a square box called the datum feature symbol.
All other surfaces of the tested item that are parallel to that surface are marked with the same letter for reference.
In machining parts, it is common to define three datum surfaces, for reference in all three dimensions of the solid object.
These will be labeled A, B and C., Your measurements will be flawed if foreign objects are allowed to interfere.
On a large scale, something like sand or other visible objects on the datum will prevent the tested surface from sitting flat.
The parallelism will therefore be measured incorrectly.
Depending on the level of precision that you need, something as minuscule as dust on the surface may throw off the measurements.
The level of precision that you need in measuring the parallelism will factor into just how clean the datum must be. , No two surfaces are exactly parallel to each other.
You must define the level of precision you require and the level of precision that you can measure.
If the two surfaces fall within that tolerance range, you then can say that they are parallel.For example, you might require two surfaces to be parallel to within a quarter inch.
This means that the measurement at one end of the surface may be a quarter inch or less from the measurement at the other end of the surface, for the surfaces to be called parallel.
If the difference is more than one quarter inch, then it fails parallelism. , If your measurement requires a very high level of precision, then slight variations in temperature may affect the parallelism of the surface.
Some materials expand or contract as the temperature changes.
Very precise measuring instruments will recommend that you calibrate the temperature of the room and the object being measured, and allow adequate time for them to reach a consistent temperature. -
Step 3: Ensure that the datum is level and clean.
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Step 4: Define the tolerance range.
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Step 5: Ensure a consistent temperature.
Detailed Guide
Parallelism is a quality that can be tested on several different types of surfaces.
These are labeled based on their positions relative to each other.
You may wish to test parallelism of the following:
Planar surface:
Opposite flat surfaces of a rectangular solid need to be parallel to each other.
Cylindrical surface:
A cylinder appears round when looking at its end, but when held upright, its sides must be parallel for the cylinder to function properly.
Parallelism also needs to be measured on the interior cylindrical surfaces of drilled holes.
The datum is a flat surface that you use as a reference.
This will be one edge or corner of the object being tested.
Measurements for the size and shape of the object are then drawn in reference to the datum.In technical drawing, the datum is marked with a capital letter in a square box called the datum feature symbol.
All other surfaces of the tested item that are parallel to that surface are marked with the same letter for reference.
In machining parts, it is common to define three datum surfaces, for reference in all three dimensions of the solid object.
These will be labeled A, B and C., Your measurements will be flawed if foreign objects are allowed to interfere.
On a large scale, something like sand or other visible objects on the datum will prevent the tested surface from sitting flat.
The parallelism will therefore be measured incorrectly.
Depending on the level of precision that you need, something as minuscule as dust on the surface may throw off the measurements.
The level of precision that you need in measuring the parallelism will factor into just how clean the datum must be. , No two surfaces are exactly parallel to each other.
You must define the level of precision you require and the level of precision that you can measure.
If the two surfaces fall within that tolerance range, you then can say that they are parallel.For example, you might require two surfaces to be parallel to within a quarter inch.
This means that the measurement at one end of the surface may be a quarter inch or less from the measurement at the other end of the surface, for the surfaces to be called parallel.
If the difference is more than one quarter inch, then it fails parallelism. , If your measurement requires a very high level of precision, then slight variations in temperature may affect the parallelism of the surface.
Some materials expand or contract as the temperature changes.
Very precise measuring instruments will recommend that you calibrate the temperature of the room and the object being measured, and allow adequate time for them to reach a consistent temperature.
About the Author
Laura Reyes
Brings years of experience writing about pet care and related subjects.
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