That's telling you how much break edge is allowed on outside corners.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

That's an ISO/DIN symbol for a sharp corner. The listed values specify maximum and minimum allowable values for an edge break, which is assumed to be 45⁰ unless specified otherwise.

rossniinisto,

This may help you:
http://files.engineering.com/getfile.aspx?folder=0...

The snapshot is from ISO 13715:2000 "Edges of Undefined Shape". I am pretty sure there is German version of that standard too.

Whoever wrote/translated that ISO 13715:2000 does not know the definition of undercut. None of those are undercuts.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

Another portion of figures from this standard:
http://files.engineering.com/getfile.aspx?folder=0...

Quote (dgallup)

Whoever wrote/translated that ISO 13715:2000 does not know the definition of undercut. None of those are undercuts.

ISO defines an undercut as any deviation from ideal form which removes material from a corner, either external or internal.

So, yes they are per ISO's definition.

Though I would agree that using the term 'undercut' to describe an external fillet or chamfer is not intuitive at first glance.

Snapshot from DIN ISO 13715:2000, hope this will help:
https://res.cloudinary.com/engineering-com/image/upload/v1504853183/tips/ISO_workpiece_edges_symbol_elements_bccrzy.pdf
https://res.cloudinary.com/engineering-com/image/upload/v1504853205/tips/ISO_workpiece_edges_examples_o4gdhn.pdf

Season

Just because some bureaucratic nincompoop wrote something into a standard does not make it correct. I've seen plenty of standards full of grammatical errors. Sometimes they are flat out wrong. In this case, probably a bad translation from the original German.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

The definition I used above is stated explicitly by ISO- it's not a translation error. This is deliberate.

As I said I agree that it's not an intuitive definition- but if you work in ISO a lot (as I do) it becomes a very convenient-- as any reduced-material corner/edge form error uses the same terminology, regardless of the surrounding geometry. This makes explaining what you want, and defining problems across language barriers, much easier than it might otherwise be.

On some types of parts, it can also make dimensioning drawings much cleaner than the equivalent part would be if dimensioned per ASTM- every corner can use the same symbols and conventions, and that one symbol can contain a lot of information.

The root of the usage of 'undercut' to describe lesser material deviations from ideal geometric form is from the design of casting tools.

I learn a new word (nincompoop )