Tag Archives: knife sharpening

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

Neolithic Knife Sharpening Stone?

On a recent trip to Italy, I was hiking around the  Geoparco Del Beigua in Liguria. It contains what is identified as a Neolithic stone for resharpening greenstone axes, among other carved stones. Actually, the entire site consists of reproduction stones, the originals removed for protection. In case you have forgotten (as I did), the Neolithic period is the end of the stone age, generally defined between 4,500- 2,000 BCE. This is right before the copper or bronze age begins.

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Explanatory text at the entrance to the site. Geoparco Del Beigua, Liguria, Italy, 2016.

Stones like this are not unique to Italy, they are found all over Europe, and are simply called “grooves” or polissoirs by archeologists. These stones were first identified as sharpening stones in the mid-19th century, though now this is debated. Some archaeologists believe they are a type of calendar or perform another symbolic function.

The explanatory text struck me as largely conjecture. The comment that sharpening was entrusted to experts is doubtful to me, as well as the idea of a sacred element in sharpening. Such a large stone, out in the open, would suggest a more communal activity, rather than ritual expert use. I’d bet that resharpening, especially stone axes, was a common enough occurrence that anyone using one would have to perform maintenance on the edge. There are many small sharpening stones from the Roman era that have a small hole drilled into them, so they can be carried with the user.

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Neolithic Sharpening Stone. Reproduction. Geoparco Del Beigua, Liguria, Italy, 2016.

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Neolithic Sharpening Stone. Reproduction. Detail. Geoparco Del Beigua, Liguria, Italy. 2016.

More troubling, is that these grooves don’t reflect the way a stone would wear down during the course of sharpening. If the axe was used in these grooves, it would dull the cutting edge.  Only by twisting the axe (which could account for in the curves of the marks) would it be sharpened.

Another problem is that these grooves would have had to be defined by some other tool before the sharpening began.  A relatively flat area of the stone would be much easier to find and use, it seems, which is the most common shape for sharpening stones. So the idea that these were a type of jig for sharpening — which would also negate some of the need for an expert to perform the sharpening — seems suspect. This was no ancient version of a Chef’s Choice  knife sharpener, which sharpens both sides of the knife at the same time.

These questions aside, what blows my mind is that natural stones are still used by many to sharpen knives. Are sharpening stones the only stone age technology still in common use in the 21st century?

 

 

 

 

How to Rejuvenate a Glazed-over Oil Stone

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Emanuel E. Ericson and Walter E. Burton Carborundum Brand Products for the Home Craftsman. The Carborundum Company: Niagara Falls, NY, 1935. My Collection.

In 1935, the Carborundum Company published a 93 page pamphlet of surprisingly useful tips and assorted product information. It also has a beautiful cover which typographically and color-wise captures the mid-1930’s aesthetic. Carborundum is Silicone Carbide (SiC), the material many (all?) synthetic oil stones are made of, and the coating on many abrasive papers. The pamphlet cost 20 cents in 1937, according to an advertisement in Popular Mechanics.

The next time I purchase an old glazed over oil stone at a flea market, I’ll try the tip below to clean it, which involves heating it to drive out the old oil and swarth.

It also contains good advice concerning the habit keeping tools sharp. Get into the habit and become “cranky”!

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Emanuel E. Ericson and Walter E. Burton  Carborundum Brand Products for the Home Craftsman. The Carborundum Company: Niagara Falls, NY, 1935.

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Losing It

At Hopes and Fears,  Jared Fischer asks a variety of educators, neuroscientists, and others the question: “How long does it take to lose a skill?”

Most of the answers are theoretical, and the main consensus is that it is dependent on the skill and how it was acquired.  Similar to the ‘you never forget how to ride a bicycle’ adage, crafts and activities that require extensive muscle memory to learn (and the least conscious attention to perform) tend to be the most durable. Many aspects of bookbinding and knife sharpening fall into this category, and these are some of the most difficult skills to initally learn.

It’s a great question, relating not only to the acquisition of craft skills, but the maintenance of them.  Some answers in the article may contain seeds of argument for institutional conservators who feel they are trapped in front of a screen and need to justify bench time. But no practitioners were ask to self-report on their own experience, so I will ask myself.

Q: Jeff, how long does it takes to lose a skill?

A: I usually don’t subscribe to the idea that various crafts and skills sets are so different that there are isolated muscle memories associated with them.  When I teach freehand knife sharpening, for example, I try to emphasize the relationship between sharpening and leather paring: the muscle memory that it takes to hold the knife freehand on the sharpening stone is closely related to the way you need to consistently hold the knife to pare. So in many regards, I think if you are active in some craft activity it can slow the erosion of neglected skills in another.

That said, when I was a kid I tried to learn how the juggle one summer.  It seemed like hundreds of hours were spent, essentially in failure.  But the next summer, I picked up the three balls and for some reason it just worked.  Juggling may be pure muscle memory, since it primarily depends on how accurate you throw the ball.  Now when I try it, I am not nearly as good, but can keep the balls in the air for a short time and suspect if I kept at it could return to a basic proficiency. So in this case, the skill is severely degraded, but not lost.

A dispiriting aspect of this question is that one’s intellectual knowledge of what constitutes skillful performance often increases during the time that the physical ability to accomplish this decreases.

Well worth reading other perspectives:  “How long does it take to lose a skill?”

Review of “Sharpening for Conservators” Workshop

Dan Smith wrote this review for the Guild of Book Workers Newsletter, April 2015, No. 219. If you are not a member of the Guild, you are missing out on a lot of other things: workshops all over the US by professional bookbinders, a bi-monthly newsletter, an infrequent journal, a secret handshake, and a yearly conference.

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Having an Edge: A One Day Workshop with Jeff Peachey

Review by Daniel Smith

I often wondered why such an important component of bookbinding—sharpening, seems so overlooked in workshops and general instruction. Dull knives can be the source of great frustration. Jeff Peachey has spent much of his career fixing this situation. He ran a one day workshop recently at The Conservation Center on the Upper East Side of Manhattan demonstrating his technique. Here’s what I learned.

We were given a choice of right or left hand English paring or Swiss knife blanks to work on. All had been machine ground to the correct bevel of 13 degrees and our assignment was to sharpen and hone the blade.

Thou shall not round the bevel.*

If uneven pressure is applied while sharpening, the bevel can develop an obtuse roundness that requires a regrinding to remove. This is the most common mistake. This problem can be avoided by placing the knife bevel side down on the film and pushing down on the edge and allowing it to lock into the proper angle. This is something you need to get the feel for.

Thou shall sharpen side to side.*

The idea is to use increasingly finer grades of abrasive film (3M Microfinishing film) to achieve the finest edge. The strips of film are mounted on Delrin, a plastic with hardness and rigidity like steel. The film is backed with a pressure sensetive adhesive that allows it to be reused. The first grade was 80 micron. This was used until all the deeper gouges from the machine cut are removed.  This stage is the easiest to see the difference between the old surface and the new. It also takes the longest. Four fingers hold down the blade edge as you pull it side to side across the film using plenty of water as a lubricate. The water darkens with the tiny particles of steel that are removed from the knife called swarth. This is the aluminum plate sharpening system found on Jeff’s web site.

Thou shall not advance to the next grit until the burr develops.*

Once you’re done with the bevel side you need to grind the flat side to remove the burr that has built up. Feeling the burr is a good way to tell how evenly you’re grinding. If there’s less burr on one side more pressure must be applied while grinding. Jeff recommends using grits half the size of the previous one, so from 80 micron we went to 40, then to 15 and to 5. It was increasingly harder to see what you’re accomplishing with the finer grits but by [feeling the burr and] careful inspection we made progress. I found the concept of creating a knife edge so sharp that it would easily pare leather a bit intimidating so I thought of the process more like polishing than sharpening.

Another aspect I found intimidating about sharpening a knife was wondering if I would have the  patience to finish what I suspected might be a long and tedious process. This was not a factor at all. Granted this was a motivated group comprised of conservation students, bookbinders and one guitar maker, [but] Jeff’s enthusiasm and knowledge empowered us and made us eager for all things that could cut.  I know a few of us felt that we were finally being let in on a great secret and that we would soon be able to exert some control over the drawer full of dull knifes in our studios. What kept me going was knowing that the final result would be a knife I could trust.

Thou shall not covet, or borrow, thy neighbor’s knife.*

Mr Peachey shared with us many of his old tools, relics from the industrial age, that’s he’s collected from flea markets over the years. Knifes made from ground down files, an instrument for carving your name in logs, a bee-keepers knife, handmade chisels, knifes for picking bananas or shaping the heel of a shoe or cutting wallpaper or rope. He explained its original function and shape and showed how the years of use by a long forgotten craftsmen has resulted in its current form. He also brought his collection of vintage double edge razor blades as well as ingenious devices used for sharpening them,

We were encouraged to bring our own knifes and sharpening equipment for evaluation and it was a mixture of relief and disappoint to learn that some of the items were useless for the purpose they were intended. Disappointment in that the item was a waste of money and time but relief to know it was the tool and not the hand. Some learned their favored items could be salvaged and were worthy of the effort.

Jeff went through the process with us with a knife of his own, showing us what to look for and demonstrating the proper way to hold the blade. evaluating the progress with comments like “Now I could sell this knife.” We were well into the work when Jeff finished his and demonstrated the cutting ability. The moment we had been waiting for. Gasps went out as his knife pared the leather perfectly, and well, there’s no other word for it, like butter. We returned to our work with renewed determination.

Stropping the blade is the last step of the process. This is the familiar motion barbers use on a single edge razor before shaving a customer. Our strop was horse butt leather coated with .5 micron chromium oxide on the flesh side. This is a different motion than the side to side sharpening action. The knife is held perpendicular and pulled away from the substrate. Properly sharpened knifes can be stropped to produce a very sharp final edge. Double edge razor blades can be stropped to restore its sharpness.

My knife is now a prized possession, cuts leather beautifully and nice to look at. A bit of stropping brings the cutting edge right back into form. Final lesson: It’s a major faux pas to borrow a colleague’s paring knife, so don’t ask.

* from Peachey’s Ten Commandments of Sharpening

The Guild of Book Workers Website