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A capital R before a dimension, marking it as a radius.
Also known as: Letter R on a drawing
R before a number means radius. Arcs are dimensioned by radius and full circles by diameter, which is a convention about what can actually be measured on the finished part rather than a matter of preference.
States that the dimension it precedes is a radius, measured from the centre of an arc to its edge.
Contexts: Technical drawing
Is used for arcs where the diameter symbol is used for complete circles, a division that follows what can be measured on the finished part.
Contexts: Technical drawing
A capital Latin letter R placed immediately before a numeral, with a leader line running from it to the arc it dimensions.
A fuller structured visual breakdown is not yet documented for this symbol.
The paired ways of dimensioning curvature.