We report on the conversion of the Hamburg Dependency Treebank The HDT consists of more than 200.000 sentences annotated with dependency structure, making every attempt at manual conversion or manual post-processing extremely costly. The conversion employs an unranked tree transducer. This formalism allows to express transformation rules in a concise way, guarantees the well-formedness of the output and is predictable to the rule writers. Together with the release of a converted subset of the HDT spanning 3 million tokens, we release an interactive workbench for writing and refining tree transducer rules. Our conversion achieves a very high labeled accuracy with respect to a manually converted gold standard of 97.3%. Up to now, the conversion effort took about 1000 hours of work.