Just Looking

Once a year I teach a knife sharpening and tool making workshop in the bookbinding department at North Bennett Street School (NBSS) in Boston.  NBSS has the finest bench oriented two year bookbinding program in the world. If you have the passion, drive, commitment, dedication — and are crazy enough to pursue this antiquated profession in the 21st century — this is the place to do it. You will find many kindred spirits in your cohort.

I cover all aspects of sharpening related to bookbinding: blade angles, bevel angles, types of steel, types knives, types of grits, grit progression, hand grinding using power tools, free hand sharpening, and stropping. These techniques can be adapted to virtually any type of sharpening system: oil stones, diamond stones, waterstones, lapping powders and finishing films. Free hand sharpening throws many students into the deep end, for a while, but ultimately equips them to sharpen most types of edge tools. Most bookbinding knives have complex shapes and handles  which preclude the use of jigs or honing guides.

The foundation of this class is critical looking. Critical looking is not only closely watching the instructor demonstrate a technique, but it is looking at what you have done. Often when sighting or aligning, one eye is better than two.

Once you can visually analyze what your hands have done, then you can correct, alter, adjust, repeat your hand technique. Critical thinking is taught via writing in undergraduate curriculums. Could critical looking be linked to drawing?  Taking a photo or shooting a video can be a useful shortcut for note taking that may gloss over important aspects, such as processing and replicating. Drawing really forces you to look closer, again and again and again.

Critical looking is different from just looking. In a narrow sense it means learning to interpret what you are looking at, what the scratch patterns, reflections, divots, rounded bevels mean in relation to how you were holding the knife. In a broader sense it means understanding  what the effect of your actions are. Critical looking is the basis of all sharpening, maybe all craft skills?

 

Below are some images of the 2017 workshop shot by Brian Burnett.

 

All Photos Copyright 2017 Brian Burnett. And he was critically looking.

 

Twelve Ways of Testing Knife Sharpness

1. Visual inspection. When looking directly at the blade edge, with a light source behind you, are there any reflections? If so, these are dull, bent or chipped areas. The cutting edge should be an almost invisibly smooth black line.

2. Visual inspection, with magnification. When looking at the side of the blade, the smoother it is, the sharper it is, and presumably the longer the edge will last. Brent Beach, for example, measures wear in terms of pixels in a microscopic image at 200x. Leonard Lee’s Complete Guide to Sharpening has a number of electron microscope images of blade edges. Take heart, though, even a “sharp” edge will look like the Rocky Mountains if enlarged enough.

3. Shave a few hairs on your arm. If it is sharp enough to shave, it is probably pretty good. WARNING: THIS IS DANGEROUS

4. Rest the blade on a pen held at a 15 degree angle. If the blade, with just the weight of the knife catches the plastic, it is sharp. If it slides off, it is dull. The closer to parallel the pen and the knife are, the sharper the blade is.

5. Do this same test holding the blade and GENTLY and see if it catches on your fingernail.  WARNING: THIS IS DANGEROUS.

6. Tsujigiri. This test likely seems a myth. Supposedly, at one time, samurais tested their swords by the number of torsos they could cut through in one stroke. The sharpest one was a #5. WARNING: THIS IS DANGEROUS, IMMORAL AND ILLEGAL.

7. For kitchen knives, see if they can penetrate a tomato or onion, with no downward pressure and no sawing. There are many variables in the toughness of the skin of a tomato though, I imagine.

8. Longer blades can be tested by slicing paper, even toilet paper. There are many youtube videos of this. Slicing cardboard, because of its consistent and abrasive nature, is often a field test of edge durability.

9. Feel the edge ACROSS THE BLADE with your finger, applying virtually no pressure. The smoother it feels the sharper it is. You should be able to feel any slight irregularities, indicating  a dull area. WARNING: THIS IS DANGEROUS.

10. Test it on a difficult to cut substrate like styrofoam, cork, or balsa wood.

11. Send the knife to CATRA. They will qualitatively test for initial cutting performance, edge durability, and edge geometry. This will, however, dull your knife, so it is designed for production samples.

12. Possibly the best test is just to use it. Providing you are familiar with the material you are using it on, you can often tell instantly if it is sharp depending on how much force you have to apply.

NEW! For Sale: Sharpening System 3

There are three major improvements to this Sharpening System: Delrin plates for easy removal of used finishing film, an upgraded tightening knob, and larger feet for added stability. I’ve tested this new system for over a year for all the knives I make. Verdict? Excellent, IMHO.

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Sharpening System 3. End view with Delrin plates.

First, and most importantly, the support plates for the microfinishing film are now made of Delrin instead of aluminum.  This makes it possible to easily peel off the worn finishing film without using solvents or a fair amount of elbow grease. It stays flat, and doesn’t dish out. The microfinishing film stays in place when in use. The Delrin plates are first machined, then hand lapped. They are 12″ long, 2″ wide, and 3/4″ thick.

 

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Sharpening System 3. Detail of the precision knob.

The second upgrade is to the adjustment knob.  Previously, it was simply tapped through the end of the stand, with a coarse thread.  The new adjustment knob is made from stainless steel, has a very fine pitch, threaded through a phosphor bronze bushing. There is virtually no backlash, and nothing to rust. The end of the threaded rod contains a rounded ball, which prevents torquing of the plate while tightening. I’ll be the first to confess that this optical grade adjuster is not absolutely necessary, but, man, it is nice! Like a manual focus Leica lens.

Precise and accurate tools help perform precise and accurate work. At least, his is how I rationalize expensive tools… .

Lastly, in order to make the stand a bit more stable, the hard rubber feet are now one inch wide, with a flatter profile, giving more anti-slip contact with your bench. They can also adjust a bit to level.

This Sharpening System is a quick and convenient way to sharpen,  resharpen and keep all your knives and edge tools in peak condition, from scalpels to scimitars, plane blades to plough blades. This is a lightweight, easy to store and unbreakable system. Perfect for travel and classroom use, since there are no expensive stones to dish out, glaze over, or break.

The 3M finishing film cuts all modern high tech steels quickly and evenly. Replacement 80 micron film is available from Rio Grande; the 40, 15 and 5 micron from Tools for Working Wood.

 

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The system contains everything you need: a sharpening stand, two Delrin plates, four 11 x 2″ strips each of 80, 40, 15 and 5 micron 3M PSA micro finishing film, a 12 x 2″  Genuine Horsebutt Strop, and 1 oz. bar of green chromium oxide honing compound.

SHARPENING SYSTEM 3:  $285.00      Order here