R MIN Minimum casting fillet radius

How to verify

Radius gauges placed in the corner, which is the practical option on a cast surface, or comparison of the part scan against the model when the radius is large or the area is hard to reach. On a rough surface the gauge rests on the peaks, so it is best to check at several points along the junction and take the worst case.

Workshop guideline values

General

Radii on the order of 3–6 mm at wall junctions in sand castings.

Accuracy

Radii on the order of 2–3 mm with finer molding processes.

High precision

Smaller radii only with investment casting or die casting, where the mold can reproduce them.

Guidance only: the drawing's value always wins.

Common mistakes when interpreting it

• Reading it as a nominal radius instead of a minimum: a larger radius is usually acceptable, a smaller one is not.
• Applying the cast radius to corners that are machined afterward, where the tool radius and the drawing callout govern.
• Rounding by hand with a file or grinder to meet the note, leaving a transition that is neither measurable nor uniform.