Roundness applies to each cross-section separately on a cylinder surface in a round feature, e.g. in a hole or on a shaft. By means of the roundness tolerance, the radius variation for the form of the cross-section is restricted.
Definition of roundness
In each cross-section, the outline shall be contained between two concentric circles a distance t apart.
Coaxiality / Concentricity
These tolerances are special cases of position when the tolerance applies to the centre point or axis of a hole or a shaft and the theoretically exact position coincides with the datum or the extension of the datum.
Definition of coaxiality
The axis shall be contained within a cylinder of diameter t. The axis of this cylinder coincides with the axis of the datum.
Coaxiality is used when two cylinders are to be in line with each other and where one constitutes datum for the other. It should be noted that the tolerance applies to the axis of the abstract feature and not to the actual cylinder surface. This is what distinguishes coaxiality from radial run-out.
Definition of concentricity
The point shall be contained within a circle of diameter t. The centre point of this circle coincides with the centre point of the datum.
In principle, concentricity is the same as coaxiality but is used when the tolerance applies to the centre point of a cross-section and not to an entire axis. If what you measure is a cross-section, the tolerance zone will be a circle instead of a cylinder.
Circular run-out (radial)
The run-out tolerances are a type of “mixed tolerances” where different types of deviations are limited by one and the same requirement. They can be divided into run-out in the radial orientation and run-out in the axial orientation. Both of these types can be divided into circular runout and total runout respectively. The difference between circular and total runout tolerances is that circular runout tolerances only apply to each cross-section separately while total runout is measured over the entire feature.
Runout tolerances are usually applied to parts that rotate around an axis of rotation which
constitutes datum and can generally be described as a tolerance for how much a surface may vary during one revolution.
Definitions of circular run-out (radial)
The outline in any cross-section shall be contained between two concentric circles a distance t apart. The centres of the tolerance circles coincide with the datum.
The actual form of the tolerance zone is the same as for roundness. The difference is that at runout, the tolerance zone must be concentric with a datum shaft. At roundness, the tolerance zone may be moved along if the toleranced feature is moved from the centre of the datum. Circular runout (radial) thus sets a limit for out-of-roundness since the appearance of the tolerance zone is the same as for roundness, but it also sets a limit for eccentricity since it must be centred with a datum feature.
PC-DMIS CAD++ 2o14 SP1
hahaha, very funy. He could be right that his parts are good since my relationship is off from probe to probe, but still he is DUMB moth...er