Hi Gentlements,

Would like to ask for advice:

I am desperatly trying to sketch this situation shown on attached picture.

The goal is to have curve/spline tangent to both circles. Point is that the "gap" betwen curve and construction circle have to gradualy come from gap 10mm to 9,8mm on its way. Thanks for any idea.

There are a multitude of possibilities that fit your criteria. Try using an arc of radius 55mm. Make it tangent to both circles.