1 - Thou shalt not round the bevel or the back.
2 - Thou shalt not use jigs.
3 - Thou shalt look at the scratch patterns in the metal.
4 - Thou shalt use a bevel angle appropriate for the knife and task.
5 - Thou shalt not covet, or borrow, thy neighbour's knife.
6 - Thou shalt sharpen side to side.
7 - Thou shalt use a grit progression and entire surface of the stone.
8 - Thou shalt not let thy sharpening system become glazed over.
9 - Thou shalt not advance to the next grit until the burr develops.
10 - Thou shalt not insult thy neighbour by insisting on the absolute superiority of any technique or system.

COMMENTARY

1 - Rounding the bevel, or the back, or both(!) is the most common mistake in sharpening. Even Though the knife may look 'sharp' -ie. polished-it will not cut if the included angle becomes too obtuse. Even with continued, careful stropping, eventually the knife will need to be reground and resharpened. Of course, there is back bevelling, a specialized form of blade geometry, which must take into account the change in the included angle on the bevel. In practice, a small amount of rounding always occurs: the goal should be to minimize it.

2 - Not relying on jigs will give you much more freedom, and speed, in sharpening a variety of tools. Many bookbinding knives do not fit in standard jigs, which are often designed for woodworking tools. The hand motions and muscle memory necessary to sharpen freehand are often very similar to the skills necessary to use the knife properly. Throw away your crutches and walk.

3 - Looking at the visual evidence of what you are doing when sharpening is paramount. Even slightly changing the angle of the knife when moving to a finer grit will show exactly what the new grit is doing. A 10 power magnifying lens is very revealing. Always sharpening in the same direction will disguise the effects of the new grit.

4 - Always use the lowest possible blade angle for the task at hand. For paring leather, this is around 13 degrees.

5 - Knives are very personal. You need your own, and get to know how to use and sharpen the particular angles it develops. Most people sharpen with small idiosyncratic deviations from a geometric ideal, and learn to work with these deviations in practice. A well made knife will last the rest of your career, don't purchase or make an inferior one. In the bookbinding world, it is a major faux pas to borrow a colleague's paring knife.

6 - It is much easier to maintain a consistent bevel sharpening side to side freehand (parallel to the cutting edge), rather than sharpening from the cutting edge to the start of the bevel, perpendicular to the length of the blade. I have noticed this in student work as well as my own. This does necessitate a flat stone or sharpening surface, however. Of course, it is possible to sharpen in almost any direction, as long as your hand is comfortable and you are able to maintain a consistent angle.

7 - It is much faster and easier to have a series of small grit progressions, rather than one or two large ones. Always buy the longest stone you can afford and use the entire surface of it moving the blade 10 inches once is basically the same as moving the blade 2 inches, 5 times.

8 - Always use a lubricant. A glazed over system will generate heat and cut very slowly.

9 - Feeling, or looking for the burr lets you know that the two planes have exceeded the point where they meet. This assures you there are no flat (dull) areas on the cutting edge. With very fine grits it may not be possible to feel or see this.

10 - Almost any sharpening system can work, if you know what you are doing. I've seen people break every one of these commandments and still get a great edge.

Jeffrey S. Peachey is the owner of a New York City-based studio for the conservation of books and the inventor of conservation tools and machines. He is a Professional Associate in the American Institute for Conservation and was Chair of the Conservators In Private Practice. For more than 20 years, he has specialized in the conservation of books and paper artefacts for institutions and individuals. He is a consultant to major libraries and university collections in the New York City region and nationally. He was the 2011 Sherman Fairchild Conservation Research Fellow at The Morgan Library & Museum. Current research interests are the tools and techniques of eighteenth century French bookbinding. He maintains an active blog and sells custom made bookbinding tools at jeffpeachey.wordpress.com