Definition Radius and Full Radius - Need a definition for each and difference(s)

Proud Liberal

Quite Involved in Discussions
I recall reading definitions for radius and full radius. I simply can't remember what differenciated the two. I've Google searched this and checked in the ANSI Y14.5 (no luck).

Can anyone post the two definition or at least point me to a source where I can find them?
Last edited:

Jim Biz

Maybe other publications will give you a clearer look at what you are seeking - but I would first check in any version of the "Machinist Handbook" - (Dont have mine handy right now - but I'm sure there would be informtion there clearing it up for you.

Hope this helps


Quizzed my engineer son on this; his reply follows:

A full radius (sometimes called a true radius) usually refers to a hole in the face of an object that is at an angle, and you need to ensure that the radius called out is true to the surface.

I can't verify the accuracy, but how it helps!


Bill Ryan - 2007

From "Geometric Dimensioning and Tolerancing" by James D. Meadows:
  • The local note "True R" precedes the numerical value of a radius when it is shown in a view that does not show the radius' true shape.
  • The tolerance zone created by the symbol "R", its value, and tolerance is defined by two arcs that represent the minimum and maximum value of the radius. The surface of the radius simply must reside between the two arcs to be acceptable.

Hope that helps



Radius definitions I work to:

A radius is an arc bounded by it's max and min limits and located either by tangency points with adjacent surfaces, or by a specified origin point on the drawing. It can't have flats or reversals, and usually has finish requirements.

A full radius has adjacent tangency points that make it 90 degrees of arc.

A true radius, as already stated, is called out when a drawing view has a foreshortened radius depicted.

Hope this is useful.
Top Bottom