A full radius is a radius that smoothly blends into another surface. Full radius is most often specified in a rounded slot feature or a feature that mimics a rounded slot.
A full radius sometimes noted as a true radius or full R is outdated language and not part of the current revision of the drawing standard ASME Y14.5. The full radius callout is referencing a smooth transition from the radius to an adjacent surface.
How to measure a full radius
Because no reference standard documents the requirements of a full radius, there are no specific requirements for the callout.
When a full radius, true radius or full R is called out on the drawing, the blueprint drafter is attempting to control the blend into and out of the specified radius.
Full radius vs radius
There is no difference between the drawing callouts of full radius, true radius and radius. Because there are no specific requirements for a full radius referenced by any drawing or GD&T standards, there is no difference in the requirements of a full radius or full R vs a radius or R. A full radius does not have a tolerance. A radius if drawn correctly will have some form of a +/- tolerance or be controlled through a GD&T requirement such as profile or cylindricity.
There is no difference between the requirements of the example below or the previous one.
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