depends on the steel, the heat treat, and what you'll be cutting. Usually the 30-40 degree range is recommended, with the "better" steels being better down towards 30, and the softer steels up around 40. It depends on your personal preference, and your tools at hand also. I have a sharpmaker to do most of my touch ups, so I aim to have most of my edges in the 30 inclusive range, but do most touchups on the 40 degree setting for ease of sharpening.