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PERPENDICULARITY
ORIENTATIONControls how square a surface or axis is to a datum
⚠ DATUM REQUIREDASME Y14.5-2018 §10.6
Perpendicularity controls how much a surface, line, or axis can deviate from being exactly 90° to a datum plane or axis. Like parallelism, the tolerance zone is two parallel planes or a cylinder (with ⌀) oriented perpendicular to the datum.
WHEN TO USE IT
Use perpendicularity on walls, pins, or bores that must be square to a reference surface — such as mounting bosses, threaded holes, or mating flanges. It is one of the most commonly applied orientation controls in mechanical design.
COMMON MISTAKES
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Omitting the datum reference — perpendicularity always requires a datum✕
Using ± angular tolerances on the same feature — this creates competing tolerances and over-defines the feature✕
Forgetting the ⌀ symbol when the tolerance zone applies to an axis✕
Applying perpendicularity redundantly when position already controls the orientationIS YOUR CALLOUT CORRECT?
Check these before releasing your drawing.
Does the FCF include at least one datum reference?
Perpendicularity always requires a datum reference.
Is there no conflicting ± angular dimension on the same feature?
A ± angle and a perpendicularity FCF on the same feature creates a competing tolerance — remove one.
If controlling an axis, does the FCF include the ⌀ symbol?
Axis perpendicularity uses a cylindrical zone and requires the ⌀ symbol.
OTHER ORIENTATION CONTROLS
Redprint checks perpendicularity automatically
Redprint catches missing datum references, competing angular tolerances, and missing ⌀ symbols on perpendicularity callouts.