A formed end locates a joint, it does not seal one. Asked to act as a reducer, correct a bad cut or absorb misalignment, it fails at the transition every time.
A bend has already worked the material and left its own springback. Holding the leg true, keeping the transition clear and checking against the bend decide the part.
Diameter, roundness, length, squareness and flare angle can all be checked with hand tools if you take the readings in the right places and write them down.
A second pass on the same end takes ductility and wall that the part will want later. Bead order, an anneal between passes and the scrap decision all matter.
Sequence is a process decision the drawing never states. Forming after welding pulls a heat affected zone through a shape change, and the strain goes to its edge.
Diameter gets specified and length gets assumed, yet length decides where the clamp sits and how much material has been worked. Short ends concentrate everything.
Thinning, work hardening and residual stress all land in the same few millimetres where the taper ends. That is why the crack starts there and not at the mouth.
A cone seat seals on geometry rather than clamp force, so the flare angle and the seat have to match. Where the contact band lands tells you whether the joint will hold.
