# Is it possible to connect two spheres at tangents?

Firstly I thought this will be simple one button operation, but apparently it’s not.

Their centers placed on completely different axes, so I can’t just use Line: Tangent To 2 Curves with planar circles, then Revolve result. And I don’t see an appropriate tool.

Pipe with rounded caps gives imperfect result too.

• Draw a line between the two sphere centers
• On each endpoint of the line, use Circle>Around curve (with the line as the curve) and use the diameter of the corresponding sphere.
• Use the two circles so obtained to trim off the unwanted parts of the spheres
• Loft between the two open sphere edges to make the connecting cone

There are other, similar ways…

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sorry @Helvetosaur with trimming the spheres as you suggest, there will be half of the sphere, and the connection will not be tangent (the big sphere has to "contribute more then 180 degree, the smaller less then 180…)

so maybe one of those other ways:

• Draw a line between the two sphere centers
• set the _cplane by x-axis from center to center.
• redraw the circles - corresponding to the spheres
• connect them with a tangent line
• extend the axis to trim the circles, join the resulting curve
• do a revolve (marked / yellow in the screenshot)

(sorry i reversed big and small radius, but the workflow is the same…)

i left the c-plan orientated in the screenshot…

hope that helps - best -tom
Mace_Keule_00.3dm (148.3 KB)

Brilliant, thank you. CPlane did most, allowing me to use ordinary Line tool on unusual axis.

OK, I must have really been asleep at that point, sorry…

• Create the axis line between the two sphere centers.
• In one of the orthographic views, call the command CutPlane and snap to the two endpoints of the line (it doesn’t matter from which view, actually).
• Intersect the plane with the two spheres, use SimplifyCrv on both results to make circles
• Use Line>Tangent to two curves to make a tangent line between the two circles
• Revolve the tangent line using the center-to-center axis, full circle
• Trim and Join to form a closed solid (BooleanUnion will also work if the cone normals face outwards)

Even less stuff: Use `InfinitePlane` to make the intersecting plane.

-Pascal

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InfinitePlane is an option instead of picking a surface…

nice - did not know this-one thanks @pascal
but _cplane s are powerful also

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