The diameter of a Tapped Hole is determined implicitly. Tapped Holes are selected from a set of predefined combinations, where ThreadType and ThreadDesignation determines the Size parameter. If you want a different 'Size' value then you have to select all the other appropriate values in the HoleTapInfo object.
Dim oDoc As PartDocument = m_inventorApplication.ActiveDocument
Dim oHTI As Inventor.HoleTapInfo
'this combination sets the thread Size to 0.0551
oHTI = oDoc.ComponentDefinition.Features.HoleFeatures. _
CreateTapInfo(True,
"ANSI Unified Screw Threads", "140-85 UNM", "2B", True)
oDoc.ComponentDefinition.
Features.HoleFeatures("Hole1").TapInfo = oHTI
