I asked Josef about the Knuckle frames that I had seen that were half furnace brazed, and half electric welded.
He told me that with all the technology that had come out of Harley's involvement in the war effort(WWII), Harley had decided to do away with their furnace brazing, and assemble all their frames - starting with the '48 Panhead models (then on the drawing boards) - using the latest electric welding methods.
He said that starting around mid- '46, Harley started phasing in electric welders on the frame assembly, But because they couldn't shut the entire frame department down to re-train all workers at once, Harley sent some of their crew to weld school, and when they were finished, another group would go.
So, some of the men were trained and some weren't.
The welders would electric-weld part of the frame, and the brasers would still furnace-braze the axle plates, neck forging and seat crossover tube, until all the men had rotated through welding training.
Josef said after mid-'47, every frame was totally electric welded, except for some Servicar frames.