In the schematic, the cutter bar is shown from a top-down "exploded" view. You will see the seven disc assemblies.

He didn’t have a new internal shaft. But he had a welder, a lathe, and a stubborn heart. Using the diagram’s measurements, he fabricated a temporary pin. He replaced the broken shear hub with the spare he kept on the high shelf, a spare he only knew to buy because the diagram had a big red circle around “Item #22 – High Wear.”

Some aftermarket discs have a different bolt pattern. The diagram’s hub dimension (e.g., 6-bolt on 120mm circle) is your only safe reference.