Keep in mind that Pete is talking about a custom made billet cam core - usually made out of AQ/BQ 8620 steel. The initial operation is to make a cam core (lobes, journals, etc) - but oversize in the journal areas. The journals and lobe areas are just round pieces of steel at this point, no "lobes" yet exist.
The cam core is copper plated (the whole core), then it is "rough ground" (lobes and journals) to about .030 oversize (on everything), then it is heat treated to harden both the bearing journals and the lobe surfaces.
The copper plating prevents the hardening from going into the core of the shaft - such that it doesn't become brittle. After the rough grind and heat treat, then the cam is finish ground to the final profiles and journal sizes. This multi-step process is one reason why custom billet cams are much more expensive than typical cast-iron versions.
Here is a cam "core" that has been copper plated - it is for a Flathead Cadillac engine that I built:
Copper Plated Core:
camz3.1.1.JPG
Finish Ground:
cam3.1.jpg
Here are two Flathead Ford cams: An Isky 404A (cast-iron core) and an Isky 505 custom billet core - .505 lift and large bearing journals (only way to get that amount of lift!). Pete did the finish grind on the 505 - thanks Pete!