Tag Archives: knife sharpening

New! Aluminum Plate Sharpening System II

I’ve made three significant improvements to the aluminum plate sharpening system. First, the plates themselves are now a half of an inch thick, rather than a quarter.  This aids in their stability if used without the holder. Secondly, the plates are now machined with a flycutter, which results in a flat surface and regular pattern.  Thirdly, the plate holder has been redesigned. Now, a knurled adjustment knob allows quick and easy flipping and switching of the plates without tools. It now only takes 3 seconds, even if you work slow. The stand is all aluminum with stainless steel screws so there is nothing to rust.

These plates are used the same as any sharpening stones. The plate holder has four rubber feet to keep it from sliding around. I generally use water as a lubricant to keep the metal particles from glazing over.

This is the system I use to make and sharpen all of my knives. People often ask how long each abrasive sheet lasts, and although there are many variables, I’d guess I can generally sharpen about 10 knives on each one. Of course, if you are trying to reshape a bevel angle or repair a major chip you might use up an entire sheet. When a sheet is exhausted, simply peel it off and stick a new one one. You must trim the edges of the edges of the finishing film when you put a new sheet on, so that it does not overhang the edges. Otherwise it may give you one of the nastiest, dirtiest, slow-healing cuts you have ever had, DAMHIKT. 80 micron replacement sheets are available from Rio Grande; the 40, 15 and 5 micron from Tools for Working Wood.

I’m convinced it is the easiest, quickest, and most convenient way to resharpen and keep all your knives and edge tools in peak condition, from scalpels to scimitars. This system is a lightweight, easy to store and unbreakable. Perfect for travel and classroom use.

The system comes with 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 buffing compound. The entire system is 13 x 3 x 2.5″, 3 lbs. 4 oz.

ITEM #SS2: Introductory price  $225.00

Tips on sharpening are located here, and tips on stropping here.

Hand Stropping

Above: The Art of Preserving the Hair, On Philosophical Principals.  By the Author of the Art of Improving the Voice. (London: Septimous Prowett, 1825), 250-251.

Before you try this, think of the way your strop gets to torn up in use!  I have tried hand stropping—very carefully—but didn’t notice much difference in the sharpness of the blade as compared to stropping on an undressed vegetable tanned hair side skin, to be honest. Hand oils may give the steel a bit more resistance to rusting. Needless to say, hand stropping is performed slowly.  I still prefer a Horse butt strop, available here.

Hand stropping lives on in various guises, however. Shaving enthusiasts have a thread titled Hand Stropping Really WORKS!. A youtube video demonstrates the stropping of a single edge razor blade. Bill Carter, a plane maker from the UK hand strops a plane blades. To be clear, he is pulling the blade away from his hand.

Below: The tough hands of Bill Carter.

How to Strop a Knife

Stropping is a motion which pulls the cutting edge away from a substrate—leather, paper, wood, etc.—perpendicular to the cutting edge, with or without additional compounds. Stropping not only produces a very sharp final edge after sharpening, but it is an easy way to renew a slightly dull edge without having to go through the entire resharpening process. I tend to strop my knives whenever they feel a bit dull, or I have to apply excess pressure when using it, or when edge paring very thin leather.  I find stropping the quickest, easiest way to keep the knives used for leather paring sharp.

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TECHNIQUE

The above video illustrates the technique I use in stropping, using the materials I will discuss below. I strop all the knives I sell using this method, and use it to keep my own knives in shape. There are two key aspects. First, always draw the blade away from the cutting edge to avoid digging into the leather, which is sometimes called a “trailing stroke”.  Second, it is paramount to hold the knife at the exact bevel angle it was made, and keep this angle consistant throughout the stroke. If you raise the angle, even a few degrees, the cutting angle will rapidly become too obtuse and you will have to resharpen or possibly even regrind it. Similarly, the back needs to be kept flat.

I find a strop that is 12-15 inch long and 2 or 3 inches wide ideal. If it is shorter you will have to reposition the knife an inordinate number of times, which slows the process and may introduce more errors.  If the strop is too long it is difficult to maintain a consistent angle on the blade throughout the length of the stroke. If the knife is slightly wider than your strop, just angle it a bit so it fits.

I count the number of strokes I do on each side to keep them even, 12-15 times on each side is a reasonable starting place.  If the knife is still not sharp, strop some more. If it still is not cutting well, it may need to be resharpened or reground. Although you are *just* rubbing a knife on a piece of leather, don’t be fooled that you are not doing anything: all the black marks are metal that have come off the blade.

Eventually, however, even careful stropping will gradually create an obtuse cutting edge. It may look sharp and have a mirror shine, but it will need to be resharpened using your preferred sharpening system.

MATERIAL FOR THE STROP

I prefer a two stage stropping. First I strop on the flesh side of horsebutt, which is dressed with a .5 micron green honing compound.  Horsebutt strops available here. Then I do a secondary, final, stropping on undressed flesh side of calf. This is why I flip the strop over in the video. I find it gives an excellent final “bite” when paring leather, though some people prefer just the hair side of the horse butt, others skip this step completly.  Other substrates for strops are wood, MDF, binders board, cowhide, mat board, etc. Anything firm and  flat can work, although a material that compresses too much will round over the cutting edge more quickly.  I prefer horsebutt over cowhide because the surface lasts longer, it is firmer, and it is a traditional material for high quality strops.

I generally use the strop on a hard flat surface but some people mount them to wood or other flat material.  Since I use mine two sided I find it easer to just flip it over.  The speed that you strop at does not seem to make much of a difference, as long as a consistent angle is maintained. There are also a variety of leather belts and discs to attach to power machinery, but I find it is too easy to round an edge using these, and it is not really much of a time savings since stropping does not take much time by hand.

COMPOUNDS FOR THE STROP

My preferred stropping compound is a .5 micron green chromium oxide buffing compound. I now sell a convenient 1 oz. bars of them, and my sharpening system also now comes with them. I like the edge this compound gives to the knife, and it does remove metal fairly quickly. Chromoglanz is another popular option among bookbinders, though I don’t know how precisely the abrasive is sized, and I personally don’t like the way it feels when you are stropping—it is very slippery. It seems to be better at polishing than establishing a cutting edge. There are other types of powders and honing compounds available as well, jewelry suppliers often have a wide variety. Quarter and half micron diamond paste is an expensive, but addictively fast cutting strop dressing and a real joy to use.

Careful stropping can keep an edge tool cutting well for a long time.

Peachey’s Ten Commandments of Sharpening

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 thy neighbors 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 neighbor by insisting on the absolute superiority of any technique or system.

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COMMENTARY

[1] Rounding the bevel, or the back, is the most common mistake in sharpening.  Though the knife may look ‘sharp’– ie. polished– it will not cut if the included angle becomes too obtuse. Even with careful stropping, eventually the knife will need to be reground and resharpened. A back bevel works fine as long as the included angle is within the desired angle. In practice, a small amount of rounding always occurs when sharpening and stropping: 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 it standard jigs, which are often designed for woodworking tools. The hand motions and muscle memory necessary to sharpen freehand is 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, often resulting in an unpleasant surprise when a final stropping reveals many deep scratches.

[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 — don’t be a rube!

[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. 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 you 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.  This also results in less wear per stone. 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. Hogging the center will wear a stone unevenly.

[8] Always use a lubricant.  A glazed 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.

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RECOMMENDED SHARPENING RESOURCES

Hock, Ron. The Perfect Edge: The Ultimate Guide to Sharpening for Woodworkers. Cincinnati: Popular Woodworking Books, 2009.

Ron Hock’s brief sharpening notes

Lee, Leonard. The Complete Guide to Sharpening. Newtown, CT: The Taunton Press, 1995.

Maurice Fraser’s sharpening notes

Sugai, Chiharu. The Chef’s Edge: Traditional Hand-Sharpening Techniques for Japanese and Western-Style Yanagi Knives. (DVD) KORIN Japanese Trading Co., 2003.

Sharpening Support Stand

For those who use my aluminum sharpening system, I recently developed a support for the plates.  Made from aluminum, four cap head screws clamp the plates securely, yet it is quick to switch them. The rubber feet keep it from sliding around on the workbench and help keep it clean. The height, 1.5 inches, gives hand and finger clearance when sharpening, especially when working perpendicular to a workbench. This is what I use to make all of my knives, although I have dedicated stands for each of the four grits I recommend.

1. $140.00 for the complete sharpening system. Includes: Sharpening stand, two aluminum plates, 5 strips of 2 x 11 inch 3M microfinishing film, a two sided horsbutt/ calf strop, and .5 micron honing compound .

2. $100.00 for the sharpening system without the stand.

3. $40.00 for the sharpening stand.

Mobile Knife Sharpeners

I see mobile knife sharpeners, generally outside of North America.  Like this man, most have ingenious, homemade mechanisms rigged up on bicycles or mopeds to both provide transportation and power the grinding wheels. I’m a bit envious because seems like nice life, riding around, getting exercise and grinding knives en plein air!  Looks like a nice acute bevel he is forming on the knife below.