I'm trying to determine what size milling cutters(ball nose) would be required to finish a body in order to estimate machining times. I'm currently using ISurface.FindMinimumRadius, but this does not necessarily return the minimum concave radius. I was wondering if anyone might have any ideas on the matter?

                ...

                vFaces = swBody.GetFaces

                For Each vFace In vFaces

                    Set swFace = vFace

                    vFaceUV = swFace.GetUVBounds

                    uBoundArray(0) = vFaceUV(0)

                    uBoundArray(1) = vFaceUV(1)

                    vBoundArray(0) = vFaceUV(2)

                    vBoundArray(1) = vFaceUV(3)

                    uBoundSuf = uBoundArray

                    vBoundSuf = vBoundArray

                    Set swSurf = swFace.GetSurface

                    numOfRadii = 0 'FindMinimumRadius isn't setting numOfRadii to 0!

                    If Not IsPartOfHole(swFace) Then

                        If swSurf.FindMinimumRadius(uBoundSuf, vBoundSuf, numOfRadii, radius, location, uvparameter) Then

                            If numOfRadii Then

                                For i = 0 To (numOfRadii - 1)

                                    If swFace.FaceInSurfaceSense Then d = -radius(i) Else d = radius(i) '+ number indicates concave curvature,- number indicates convex curvature

                                    'Debug.Print "Smallest rad for this surface "; Round(d, 5)

                                    If d > 0 Then

                                        If i = 0 Then

                                            Select Case d

                                                Case 0 To 0.0009: FaceArea1mm = FaceArea1mm + swFace.GetArea

                                                Case 0.0009 To 0.0014: FaceArea2mm = FaceArea2mm + swFace.GetArea

                                                Case 0.0014 To 0.0019: FaceArea3mm = FaceArea3mm + swFace.GetArea

                                                Case 0.0019 To 0.0024: FaceArea4mm = FaceArea4mm + swFace.GetArea

                                                Case 0.0024 To 0.0029: FaceArea5mm = FaceArea5mm + swFace.GetArea

                                                Case 0.0029 To 0.0039: FaceArea6mm = FaceArea6mm + swFace.GetArea

                                                Case 0.0039 To 0.0049: FaceArea8mm = FaceArea8mm + swFace.GetArea

                                                Case 0.0049 To 0.0059: FaceArea10mm = FaceArea10mm + swFace.GetArea

                                                Case Else: FaceArea12mm = FaceArea12mm + swFace.GetArea

                                            End Select

                                        End If

                                        If d < SmallestRad Then SmallestRad = d

                                    Else

                                        If i = 0 Then

                                            FaceArea12mm = FaceArea12mm + swFace.GetArea

                                        End If

                                    End If

                                Next i

                            End If

                        End If

                    End If

                Next

                 ...