Preamble: we're now owners of 10 acres of oak woodland, 4 of them fenced (against deer, for what it's worth--ever hear deer snicker?), and we've embarked on transforming part of the extensive orchard of weeds into something resembling a garden. The soil is red clay, variably friable. When solid, it's solid: a mattock that served well in Seattle was bent beyond recovery with a single blow. Underground critters (voles? ground squirrels?) seem not to have problems (they are a problem, but that's another issue), and sometimes the soil is quite friable (possibly because of the critters).
The question: what tiller to get to deal with the transformation of such soil into a decent bed? I'm happy to use lime-based amendment, but...one does have to turn it in.