I always wondered why trying to machine cast iron was so hard and it tended to come out so rough. That video tends to explain it all quite well.
I used to he a Pro-Line radio system user and Fox engine user way back then 1970's and 1980's. I actually did work at Pro-Line for several years a long time ago too.
Anyway back then Pro-Line was sort of the top of the line for radio systems and serious pattern flyers. Pro-Line had the really cool machined metal gymbals in their Custom Competion series of radios too. No chintzy plastic gymbals to cause problems.