Vocational knowledge originates from both research and from practice, each of which is transformed across several epistemic levels to become vocational knowledge. The several transformations of research to vocational knowledge have been described by Young and Bernstein as recontextualisations. Less well described are the successive transformations of practice to become vocational knowledge. This paper observes that practical knowledge has to be transformed across several epistemic levels to become vocational knowledge. It examines different types of literature on European artillery in the early modern period: scholarly books on ballistics which were printed in Latin, gunners' manuals which were manuscripts in the vernacular, and artillery books for non specialist readers which were printed in the vernacular. It finds that practical knowledge didn't have to be transformed just to apply it to a new context. Knowledge is transformed to a different epistemic level when it is expressed for use by a different type of actor for a qualitatively different purpose from the initial use. The paper concludes by arguing that vocational colleges and institutes have a potentially valuable role in developing vocational knowledge from practice.