Category Archives: knife sharpening

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.

Review: Sharpening Workshop Held at the Oxford Conservation Consortium, Oxford, England

I taught the two day version of my sharpening workshop, titled “Making and Sharpening Knives: A Rational Approach”  at the Oxford Conservation Consortium September 7 & 8, 2010.  Arthur Green and Maria Kalligerou wrote a nice review in the Institute of Conservation Newsletter,  November 2010.  If you are not a member of ICON, I would highly recommend joining– one major perk of membership is that each year, members are entitled to 10 free photocopies (including shipping!) or pdf’s of conservation journal articles ( or chapters of books) from the Chantery Library, which is perhaps the best book and paper conservation library in the UK. And there are two issues of their journal, newletters, workshops, etc….

The review also contains some good, practical tips for sharpening. It begins at the bottom right hand corner of the first page:  Knife Sharpening IconNewsNOV10

Hospital Grinder

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One of the many great things about New York City is the plethora of sidewalk vendors.  Recently, amidst a pile of used clothes, I saw this beautifully polished aluminum machine.  I sent some photos to mixed media artist and pathologist  Dr. Charlie Weissman and he speculates:

Never seen this exact machine, but probably dates from the era before most equipment was disposable, now it is easier to dispose of much equipment rather than try to get it sterilized completely and reconditined and sharpened. Looks too large for blood-drawing needles, but there are a variety of round penetrating devices– trocars  and such– for drawing off thicker fluids from various body sites, which could have been reused.  Bone-marrow biopsy needles could have this caliber.  Large biopsy needles for liver and prostate used to be reused. Modern  breast biopsy and brain biopsy needles can be large but they are not reused.  Looks a little large for spinal needle. Interesting.

The arm is adjustable for length, and simple slides back and forth to switch from one wheel to the next, which are three different grits.   It operates at a fairly slow speed, and since the motor is not shielded from the wheels, I’m guessing it was used dry. The clamping mechanism near the wheels forms a 90 degree angle, so it was likely used for round objects.  It even came in a velvet lined, fake leather grain covered wood box with a handle. Stylistically, it looks circa. 1930’s to me.  All for $10.00!

A Knife From The Hood

birck-ft

birck

At first, I thought the above knife was a German style paring knife, but now I’m not so sure. German knives are almost always somewhat flexiable, and this one is very rigid.   Notice the small recess on the handle, near the blade, perhaps worn by fingers gripping the handle over the decades.  Even a light surface cleaning could destroy not only important use evidence, but the overall beauty of the knife.  As I have said before, the over-cleaning and “restoration” of  hand tools is perhaps the most significant ongoing loss of cultural property  that commonly occurs.   The blade is full tang and has a gradual taper in thickness towards the cutting edge. Judging from the scratch patterns in the top picture, the owner must have had a stressful encounter with his grinding wheel!  But I find these marks interesting evidence of the history of the tool, as well as a visually refreshing antidote to the ubiquitous monotony of the highly regulated machine grind marks found on new tools.  The handle is an unidentified light colored wood that has been stained and is still firmly attached to the tang. The edges of the handle is still quite sharp, and the various ways I have tried to hold it all are somewhat uncomfortable.

Matt Murphy  found some information about Fred J. Birck:  “From 1903-04 he worked at 93 Essex St. In 1905-06, Fred. J. Birck is listed as being a part of Birck & Zamminer Cutlery, which is located at 154 Essex St.  In 1908-1912, Birck is listed at two seperate addresses, 132 Essex St. and 17 Cooper Sq. East. In 1912-1913, the primary address is changed to 17 Cooper Sq. E.  In 1913-1914, the partnership must have been dissolved, because only Birck is listed, and the only address is 17 Cooper Sq. E. until 1925.  Also, Mr. Birck made his home in Jersey City, New Jersey, as his address is often listed as 144 Hutton St. (Which still stands to this day.)”

So the knife is possibly from 1913-25.  Aside from the beautiful, insanely deep makers mark, I was attracted to the fact that another knife-maker worked in the East Village of NYC, only about 5 blocks from where my studio is now. There is even an old bar,  McSorley’s, established in 1854, still operating right around the corner from Birck’s 17 Cooper Sq. address. Perhaps Birck had a drink there.  I’ll raise a glass to him next time I’m there.

 

Don Rash posted a similar looking knife on his blog, unfortunately no makers mark.  I looked through Salaman’s Dictionary of Leather-working Tools c. 1700-1950 and couldn’t find any similar knives, and Salaman covers some pretty obscure leather-working trades ( ie. gut string maker, hydraulic pump-leather maker) but tends contain more English rather than American references.

 

Below is the German knife from Zaehnsdorf’s The Art of Bookbinding, 6th Ed. 1903. It almost looks like the knife is shaded more heavily on the top edge, to make clear the blade tapers toward the other edge?

german-paring-knife

Going Cryogenic

 

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Above is an example of blind stamping, using just water and the heat of the type to create the impression on a piece of vegetable tanned horsebutt leather.  The font is Edinburgh, brass type from P & S Engraving in the UK, the top line 14 point, the bottom two 10.  I’ve had these letters for 20 years, and the wear, especially on the “Y” in “PEACHEY” is evident- time to get some replacement letters!  This is the stamp on the blade cover for the new, A2 knives which has been cryogenically treated.  For more technical information about cryrogenic treatments check out nitrofreeze. Please read more about the new knives in  the new tools page on the right, and the results of testing in the post below which convinced me to use this new steel for leather paring knives.