James, especially with an edge quench I would start out with oil. The reason is that it will creat quite as big a differnce in the temperatures between the two areas as much. If the oi doesn't get the edge as hard as you need it then you may have to grit you teeth and go to water but clay coating my be a better choice with water than edge quenching to decrease the temperature between the two sections. If you have ever seen a video of a clay coated blade being quenched in water you would be amaised that any blade survives the treatment.
Doug