I'm happy to talk about modeling techniques and spend my spare time for it :)
This is MOI:a modeler first of all,not a script or math formulas container ;)

Jar tapered 6°



Rail revolve:yellow curves, profile and 8-sides as rail




Draw a polyline (yellow) always extended to avoid problems when boolean difference




Fillet the polyline to 30 mm




Extrude in both ways,once again extended as said above



Rail revolve:this will be the Jar




Turn on previous surface




Polar array:8 copies




Bool difference:subtract 8 copies and deleting



Select solid and hit fillet=5mm





Pushing fillet to 40mm




model attached,open the browser to get construction lines

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