A lot of confusion
exists over the meaning of the geometric tolerances shown in
the chart. February's Tip illustrated possible inspection
methods for position and concentricity. This month's Tip
continues with sample inspection methods for circular and
total runout and profile. these drawings is the same,
the designer should consider the needs of those who will read
the print when placing dimensions.
Circular runout requires inspecting
circular elements individually. Because of this, circular
runout will not detect changes in size. Any barreling,
waisting or taper should be ignored. These conditions will be
controlled by the size tolerance.
Total runout requires
determining the full indicator movement over the entire
feature. Total runout, therefore, detects any changes in size,
i.e. barreling, waisting or taper. Although changes in size
are controlled, the actual size of the feature is determined
and controlled by the size dimension and tolerance. A feature
may be manufactured to a very tight size tolerance but due to
eccentricity, the runout could be large. Total runout controls
form, orientation and location but not size. Profile
controls everything that total runout does as well as size if
the size dimension is made BASIC.
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