Originally Posted by
beatsal
There was a suggestion here to make the backplate with 3D printing so not sure why a lathe needed. After all, it is just a plate.
No it's not a simple plate. It has to reduce the internal volume of the engine to a minimum to maximize crankcase compression.
I don't have a Merlin myself, but I do have a Spitfire and a ME 1cc, which are similar. I'll try and arrange a photo.