As far as I know, CNC machining was being used in the aerospace industry in the 1960s. Were such machines use for the F1 engines?
At least some parts for the Apollo program were CNC-machined: e.g. the frame of the flight computer. I haven't found any documents that confirm CNC-machining was used on the F1, though.
On one hand, those engines contain thousands of parts, using all sorts of manufacturing techniques, so it's possible CNC was used on some parts. OTOH, CNC was new enough at the time to be considered newsworthy so if it was used, there'd be a story about it somewhere. My (preliminary) conclusion: CNC was probably not used on the F1 engines.
Some features of the F-1 would have benefited from CNC machining. The nozzle walls consist of a series of coolant tubes stacked together. This was a very labour-intensive process. Modern engines often use nozzle walls that have cooling passages CNC-machined into them, so you have a single part instead of hundreds.
The development of the F1 engine was started very early in 1958. The first test of the combustion chamber was done in 1961. At that time probably no computer controlled milling existed. MTBF of the computers of that time was too short to be useful for milling a part in many hours.
If some parts were milled under manual control at first why change to CNC milling later?