Hi Anthony yes I see that Rhino's filleter (both Rhino v5 and v6) does not seem to like your blade surface very much and has a gap in it at the blade's closing seam edge.

Your blade surface is not 100% exactly smooth at its closing point, there is a tangent deviation of around 0.01 degrees. It's so small that I wouldn't think it should make a difference but it seems that Rhino's filleter happens to be particularly sensitive to that. It looks like it is treating it as a sharp juncture and trying to extend and intersect the fillet pieces and that is what is causing the problem.

I think you can actually repair it in Rhino - if you extract out the fillets and untrim and retrim the fillets with an isocurve at the blade's closing seam point then it looks like the pieces join up ok. They just shouldn't have been extended and intersected. You'll also have to untrim the cylinder piece and retrim that as well.

The one made by MoI's filleter looks to be all ok to me, I have attached a STEP file export of it.

The new volume calculator for MoI v4 does not seem to have any problem with it, it says it has a volume of 8122.33 mm³.

- Michael