CR Controlled radius
Controlled radius · Indicadores dimensionales · ASME Y14.5
Example in plan
How to interpret it
On the drawing, “CR 6” states a controlled radius requirement.
What controls
A variant of the radius which, in addition to limiting size, requires the arc surface to be a smooth, continuous curve, tangent to the surfaces it joins and free of reversals, lying within the zone between the maximum and minimum radius. A regular radius allows a profile with steps, flats or abrupt changes as long as the gauges fit; this variant does not. It is used where the transition is a stress concentration point and the continuity of the profile matters as much as the size.
How to verify
An optical comparator or coordinate measurement with dense points along the arc: the criterion is not a single value but that the whole profile stays within the band between the maximum and minimum radius, with tangency at the ends and no reversals. A radius gauge is only useful as a preliminary check, because it detects neither tangency nor changes in curvature. On critical parts, inspection relies on the digitized profile of the arc.
Common mistakes when interpreting it
- Treating it as a regular radius and checking it only with a radius gauge.
- Passing the corner because the size is within tolerance, ignoring steps or curvature reversals.
- Interrupting the finishing pass right inside the arc, which is where the requirement is strictest.
How to get it in the workshop / if it comes out of tolerance
It requires you to think about the finish, not just the roughing: a corner made with two passes that leave a small step meets a regular radius but not this one. Use a continuous strategy with a fine stepover through the transition, and avoid interrupting the pass in the radius area. If the part is fatigue-loaded (shafts, section transitions, hooks), this requirement is usually what really makes it fit for service.
Profile out due to lack of tangency: the problem lies in the blend between the arc and the faces, not in the radius; correct the toolpath so it enters and exits tangentially. Steps or restart marks within the arc: avoid interrupting the pass in that area and reduce the stepover. If the surface is fatigue-loaded and transverse marks appear, consider polishing in the direction of stress when the drawing allows it.
Related symbols
Other symbols in Dimension indicators
Related tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.