Problem with fillet


Hello from Germany,
I'm a Freecad user and active member.
Many times users reported errors concerning fillets. Freecad developer and me figured out that OCC uses a different fillet type than PTC Creo, Solidworks, Catia and others. Best to see in this picture with a variable radius:
First picture Freecad variable radius:
Second picture Pro-Engineer Wildfire 5.0:

Please have a look at this problem, It's a sphere radius 25mm with a hole radius 15mm , like to see in this picture:
It's impossible to create a fillet creater than 0,05mm.

With a half sphere it's possible to create the fillets, but they are totaly different and wrong compared to ProE:
Red is ProE, grey Freecad, fillet is radius 8mm.
You can find the forum discussion with freecad files here:

Please help to fix this error.

Thank you so much and best regards from Germany


Andrey BETENEV's picture

Hello Herbert,

The reported problem is registered now in OCCT Mantis bug tracker under ID #29085, see

Should you find other cases of failure of fillets or other algorithms, please report them to OCCT Mantis directly. Note that preferred way for reporting the issues is OCCT DRAW script, as it allows developers to reproduce the problem easily. It is also OK to provide C++ code, while this assumes more efforts needed to reproduce the issue (hence less chances to get triaged soon). You can attach shapes (in BREP format) or data files in formats supported by OCCT (e.g. STEP or IGES files). Please be specific in description of the problem and provide all details to understand it and to know what is expected (as you did in this forum topic). Images illustrating the problem are always welcome; they can be attached to the issue.