My current skill level is causing me a bit of grief when trying to define a drawing to use in a design table.

I'm trying to draw a sanitary spool, but in the sketch phase I'm having issues defining the drawing so that when I change a dimension it'll change the entire sketch.

Right now when I change a couple of dimensions it'll mangle my drawing. My biggest problem is the gasket groove, I can't find a relation or dimension that will work to keep the half-circle used to cut the groove in relation to the rest of the sketch.

Does anyone know of any good tutorials on fully defining a sketch? so things don't get mangled from changing a simple dimension like height?