Plus I believe you'll need different tooling for either EI or C/Double-C cores.
Learn to make a good R-core too.
EI and C-core are actually really similar when it comes to winding and would not need much different tooling.
R-cores however are really different since you wind it while the bobbin is on the core. I have some ideas on how to wind R-cores without buying a specialized machine but that's later. Plus there aren't really ungaped r-core transformers that I know of so I wouldn't be able to make a single ended transformer with them, unless its parafeed.
Really the only one I won't attempt are toroidal since I either need really expensive specialized machinery or I become a masochist and do it by hand.
