I spent some of the weekend making these parts.
Making parts with only parts of circular features is a bit of a pain with manual machines designed for cutting straight lines (milling) or round things on a lathe.
You start by calculating the coordinates of where the edge of a circular cutter will intersect with the profile that you want to cut. Spreadsheets can be very useful for this once you have the maths correct.
Once you have a list of the coordinates like this:-
You set pairs of x y coordinates and make a cut, move to the next pair and repeat. This table covers 90 degrees of the circle. For the rest of the profile, the numbers are the same you just flip the sign, remembering to stop when the curve turns into a straight line or other different part of the profile.
Then it is a case of hand work with files and emery to blend the surface into a smooth curve like this.
Can you work out what these parts are for? Clue: it's relevant to my recent other project.
Bob