Forming holds shape and repeatability; it cannot hold flatness, position or concentricity. Where the two processes divide, how error stacks up along a tube, and why a machined pad rescues a formed part.
A burr is the byproduct of the cut, not an accident. What a loose fragment does inside an exhaust, where a cross-hole hides its burr, and why inspection plans never see the edge that actually matters.
Welding moves metal, so a thread cut before a weld and a thread cut after it are not the same thread. Order of operations, chasing versus cutting, and why sensor threads need the seat face in the same setup.
Three axes reach any point in a box; the fourth and fifth buy access rather than accuracy. What a tilting setup changes, where extra axes earn nothing, and how many directions the drawing really needs.
A bent tube is a spring, not a rigid body. How springback, clamp pressure and overhang decide whether a machined end comes out round, and why locating from the bend beats locating from the cut end of the tube.
A fabricated exhaust part is joined from stock; a machined one is cut from oversize stock. What machining actually adds, where fabrication runs out of accuracy, and why the datum, the fixture and the order of operations decide the result.
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.
