Tag Archives: leather paring

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.

 

Thinking About Making: You, Artifact and Tool

tooluse

A work-in-progress diagram of the interactions that take place when performing a craft.

I’ve been thinking about using tools for a while now, starting in 2004 with a preliminary (and upon rereading inadequate) exploration in Vol. 1, No. 1 of The Bonefolder. Since then, the cultural literacy of tool use continues to decline. In fact, I often encounter people who think they can pick up any tool and it will work fine without any evaluation, prepping, sharpening, maintenance, etc.  If nothing else, thinking a bit more about tools before using them can lead to more successful craft outcomes.

This work-in-progress diagram summarizes some of my thinking. David Pye’s concepts of “workmanship of certainty” and “workmanship of risk” fit nicely into it; technique forms a continuum between you and the tool, not residing completely in one or the other. In paring leather, for example, using a schar-fix or Brockman paring machine involves relatively little technique from you, but resides mostly in the machine. Of course, you still have to know when to use it, and set it up and maintain it. Failure is often catastrophic, it usually works well or it doesn’t. This is the nature of the machine.

A middle ground between you and the tool might be the spokeshave.  Although a 151 spokeshave needs to be modified to work well, it is safer and quicker than using a French or Swiss knife to scrape the leather. It requires more skill to use than a paring machine, but accidents are usually small tears, or sometimes chatter, rarely catastrophic, can lead to uncomfortably small small pieces of leather.

The most risky way to pare leather overall is with a French or Swiss knife.  The locus of technique is almost entirely dependent on your skill.  It takes a steady hand and a lot of practice, but I have seen binders become suprisingly adept at it. Similar to the paring machine, failure can be catastrophic, like cutting a hole in the middle of the spine. All three of these methods of paring are not mutually exclusive, often they are all used by the same binder for various purposes at various times.

There is also room for conservation work in this diagram. Your intention on the artifact is much more limited due to ethical considerations about preserving existing information inherent in the artifact, there often has to be more creative thought put into material selection and tool use. If you are paring the leather on the original spine of a book that will be rebacked, there is little or no margin of error. A loss becomes a loss of information in the artifact. You can’t buy another one. Your tools have to work perfectly.

Materials also place limits on an original design. Often beginners want to experiment with something new, unique or unusual.  There is nothing wrong with this, but it is usually much more difficult than performing a craft activity in a more traditional manner. Unusual materials can require unusual tools.

One of the joys of craft is when the three elements in this diagram are so integrated that we think through the tool and into the artifact. It becomes embodied, a natural extension of our hands.  We often call this muscle memory, or getting a feel for something. Again to use a paring example, when you are competent, the leather pares down quite simply and easily without much conscious thought. When you first learn to pare leather, you need to conscious of how hard, soft, stretchy and thick the leather is, how sharp your knife is, the blade angle of the knife, the bevel angle of the knife, the angle you hold the knife at, where you start the cut, and the amount of leather you are cutting at one time.  This is a lot to keep track of.

I think many of us forget how much of an interplay there is between these three elements. It is important to remember that when things are not going right in any craft, it is not completely your fault, or the tool, or what you are making: it is usually an inter-relationship that can take some time to sort out. That’s one reason why we take classes to learn things.

To be continued….

 

PM-V11 Spokeshave Blade for Leather

Modified 151 spokeshaves are used by bookbinders and leather workers for reducing large areas of the thickness of leather and are especially good at creating a long gradual bevel. They are also indispensable for working calf, which is difficult to pare using a Scharf-Fix machine. I’ve been experimenting with the somewhat new Lee Valley PM-V11 spokeshave blade. PM-V11 is a proprietary steel designed for woodworkers, and reportedly has the ease of sharpening of 01 steel and the durability of A2.

I’m glad they did some testing of O1, A2 and PM-V111 metals, but have some problems with their methodologies. Most importantly, the assigning of a 0-10 rating for wear based on subjective visual examination, rather than the industry standard CATRA testing machine. Then a deceptive XYZ plotting of wear testing, impact resistance, and ease of sharpening all together creating a three-dimensional triangle. Where is Edwin Tufte when you need him?  They have developed a clever method of quantifying ease of sharpening, however. Oddly, at the bottom of The PM-V11 story page, they negate the need for testing, and lay on some aw-shucks folk wisdom, claiming that woodworkers don’t need an advanced degree in metallurgy or a scanning electron microscope to realize PM-V11 is a better blade.

In any event, I was still curious.  In order to work effectively on leather, first I reground the blade to 20 degrees using a 2 x 72″ belt grinder. Then I hand sharpened an A2 and PM-V11 blade side-by-side. There wasn’t much difference in the time it took. The PM-V11 blade did feel a little gummy, which some woodworkers speculate may be due to vanadium in the blade. Edge retention seemed quite similar, though possibly the PM-V11 lasted a bit longer. PM-V11 did seem to have slightly better initial cutting performance (sharpness), however. Most importantly, PM-V11 was quicker to strop back into action than A2; it felt more like an M3 steel.

Even though PM-V11 and A2 don’t seem to be massively different, I will continue to experiment. Both of these steels are excellent. Yet, concentrating on subtle differences can reinvigorate interest in repetitive handwork, helping to stave off the inevitable boredom which looms at the edges of all professional craft work. Or, put another way, buy more tools.

Information about the history of 151 spokeshaves. At the end of this post there are tips on how to modify and use them for leather work.

Or you can purchase a already modified 151 spokeshave and blade for leather.

leather

Note the thinness of this leather shaving from a 151 spokeshave and PM-V11 blade. Spokeshaving should produce shavings, not dust.

leather2

A display of very regular shaving morphology. A sign of a sharp blade that stays sharp.

 

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.

edges

 

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

Razor Blade Planes: An Overview

INTRODUCTION

There are three fundamental techniques of paring leather in bookbinding: using a paring knife, using a modified spokeshave and using a paring machine, such as the Fortuna, Schar-Fix or Brockman. Often various combinations of these methods are used. Learning how to pare leather not only requires learning the technique of using a knife or spokeshave, but also the skills of how to keep the knife or blade sharp. The Brockman or Scharf-Fix alleviates the need to learn how to sharpen, although some thrifty bookbinders do resharpen their double edge blades. These paring machines are best suited for making small, thin flat pieces of leather — generally for onlays, labels, quarter bindings — rather than achieving a long, gradual bevel necessary for rebacking or English style full leather bindings.

There is a fourth, somewhat obscure method of paring leather which uses a razor blade plane.  There are numerous types of these planes, dating from at least the 1950’s until today. Originally, they seemed marketed to the home handyman, now most are marketed to model makers.  But at some point in time, bookbinders discovered these planes.

I’ve found little information about the history of using these planes on leather. Jim Craven, a bookbinder in Ann Arbor, Michigan, reports he recieved a Little Giant in the 1960’s, and is not sure when he started to use it on leather.  Judith Ivry, bookbinder and conservator, says they were somewhat of a craze in the 1980’s in New York City.  Occasionally I meet a bookbinder who uses, or has used them.

This post contains observations about these planes. American, German, Dutch and English versions are represented. Next week, in part two, guest blogger Eric Alstrom, Head of Conservation at Michigan State University, will present some tips for using razor planers on bookbinding leather.

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LITTLE GIANT

 Popular Mechanics, Sept 1956. p. 78

This is one of the most common, and better made than most. As far as I have discovered, this is the first oxymoronically named tool. The logo is well done, consisting of a curious kneeling ‘little giant’ supporting its own name that is shaped reminiscent of a dumbbell. This logo is a registered trademark, and the plane I have has patent pending cast on it. The instruction sheet lists it registered with  patent number  2,781,804, which was filed in 1955 and granted in 1957. I’ve seen at least two versions of the instruction sheet.

The two planes come neatly boxed, one for curved surfaces and one for flat.  The version with the flat sole is most suited to paring leather. If you are curious about using a razor blade plane, the Little Giant would be my first choice. Mine functions reasonably well with no alterations. The Little Giant is manufactured to a higher quality, with a more precisely ground sole and overall more solid feel than other planes I have tried. The flat model has a unique recessed finger area for positioning the angle and depth of the blade, while preventing fingers from making contact with the blade when planing. The curved model has two angles, one quite sharp, one more gradual, so the two planes can be used in three different planing configurations.

The box is printed, “Uses old razor blades” and the instructional sheet includes directions on how to resharpen double edge razor blades, although it is a bit difficult to understand how these very basic instructions could be of much help to a novice sharpener, especially one who had purchased a razor blade plane possibly in an attempt to avoid having to learn how to sharpen a blade in the first place. The finger position holding the blade looks frighteningly dangerous and seems to be putting a 45 degree bevel on the blade.

These sharpening instructions, from the late 1950’s,  which accompany the Little Giant are perhaps the earliest illustration of the  Scary Sharp sharpening method. They repeatedly mention using emory paper to resharpen double edge razor blades. But is Scary Sharp just using abrasives mounted on a paper of film substrate, or is it using a progression of these?

The informational sheet included with Little Giant planes shows three vignettes of the plane in use: a man trimming a door, a woman shaving down a drawer, and a boy making a model airplane. This is a tool not only for the man of the house, but the entire family. Note that it is advertised as being “sharp as a razor”. Yes,well, it is a razor.

Roughly 75% of the razor blade planes I have found appear unused, in the original box. The presence of so many “NIB” razor planes also suggests that they were likely used, or attempted to be used once or twice, then returned to the box. Perhaps the few beat up ones without boxes — a rarity — will prove desirable to collectors. The Little Giant is the only plane that I have seen that was painted; there is a light green, a darker green, a blue, and some are natural aluminum or pot metal.

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WIL-KRO RAZOR PLANER

Billboard, Oct 22 1955

The Wil-Kro (sometimes spelled Wilkro, even on the original box) is the most commonly found razor blade plane, in my experience.  It also works well in leather with little or no tuning. While some users may be content with the three blade configurations of a Little Giant, a Wil-Kro owner gets four:  a  flat sole, a bull nose, a chisel and a curved sole plane. It is one of the smaller razor blade planes, the most innovative in design, and quite comfortable to use. The blade depth is a slightly difficult to adjust on my examples, since the blade cap is actually part of the plane. A $2.50 price sheet is boxed with the model I have, although perhaps many enterprising home handymen took advantage of the discounted price of $72.00 for a gross! The small piece labeled “Fig. 8” below is often missing on planes I have seen for sale — examine the contents of the box carefully. This piece is used in the plane configuration Figure 4 on the instruction sheet below, useful for wood, but not really for leather.

The Wilkro patent  #2289504

Granted in 1942, the patent emphasizes many of the clever design features of the multipurpose handle which also secures the blade. This is the only razor blade plane I have that has the patent number stamped on the plane body, and it is the most innovative design. The patent application later notes that the blades are similar to the blades used in safety razors, but slightly different. In the instructions provided with the plane, however, ordinary double edge razor blades are recommended. The tightening knob evidently underwent some refinements during production, and has a much more elegant, almost horn like shape which is easier to align and tighten than the wing nut on all other planes. Since the body of these planes are essentially in two pieces, some users feel they are not as rigid as one piece models, though this does not seem to be an issue when using them on leather. The patent application describes this as a woodworking tool, which is perhaps its most ill suited use.

The Wilkro came with fairly detailed instructions.  The necessity for written instructions seems to indicate either a new or complex tool, or marketing to a realtively amateur market. Like the Little Giant, use in homes, possibly as a one plane fits all, seems to be the main focus for sales. Unlike the Little Giant, users of the Wilkro are advised to replace dull blades rather than resharpen them. Since the advertising I have found for both of these are roughly contemporaneous, I wonder if there was stiff competition between the two in the mid 1950’s?

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The plane also came with this Certificate of Assurance.  It certifies that the Wil-Kro is percision made and will give many years of service.  It then guarantees this performance for exactly fifteen days from the date of purchase.  The overall size of this cerificate (152 x 71 mm) is almost exactly the same as a dollar bill (157 x 66mm) and the green ink and boarder decoration also seem to visually imply paper currency. Most Wil-Kro boxes list “Craft Master Tool Co.” as the manufacturer and the contact for the warranty. One box I have, however, does not include a warranty and lists “Winston Sales Co.” as the manufacturer on the outside. Otherwise the boxes are identical.

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SELECT PLANER

The Select seems to have undergone at least three packaging styles, and one major redesign.  I think the version pictured above is earlier than the ones below.  The packaging is similar to the Wilkro: the company information on one end of the box is almost identical in layout, the “horn” tightening nut is similar, and even the complex shape to the blade holder all recall the Wilkro. In this version, the chisel blade position at the front is functional, later it is abandoned.  The complex flat blade holder design is also simplified in the versions below. The distinctive outward flair to the sides of the plane remain constant, however.

This is a somewhat interesting tool, the example I have has two different blade configurations, a flat and curved located at the back of the plane.   The instructions, located on the side of a bag containing blade caps and wing nuts, show two different types of assembling the plane. The box states the plane is for “Tradesmen, handymen, hobbyists, housewives.” Like the Little Giant, somewhat early marketing towards women. This plane feels distinctly larger than the previous two, and doesn’t seem to work quite as well on leather.

On one end of the exterior box the plane is shown operated a third way, like a scraper or chisel plane. The plane itself seems to have a vestigial place for a stud. But is it broken, did someone removed it, or were there manufacturing difficulties?  Made in USA, no patent. There is a nice slideshow of this plane on Howies Antiques, showing the same lack of a front scraper attachment. The packaging advertises it it useful in wood, plastic, leather, rubber tile, linoleum and pressed wood.  To me, this one looks later than the Wilkro or Little Giant, perhaps even 1970’s? Another version of the Select, with ribbed finger grips on the side and a fancier knob was also made.

http://www.petermcbride.com/magnum09/img/magnum_058.jpg

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RAZA-PLANE

http://www.flickr.com/photos/galoot_frank/1624654074/

This is the earliest razor plane (if it uses a disposable razor blade) I have seen. Also the only one made from cast iron, the owner reports 3 5/8″ long, 2″ wide.  This is a very common size for most razor blade planes.  I’m unclear how the blade clamping mechanism might work. There is a general thread about razor blade planes in the Old Tools Archive.

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ZIP PLANE

Modelflight

Made in England.The blade looks pretty easy to adjust from the sides. Marked Patent Pending. Like the Wil-Kro, the proper direction for planing is cast into the plane, which to me indicates a very low expected competence from users.

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DAVID (COMBI) PLANE

Dutch. Often regarded as one of the better old razor planes by model airplane makers. Three blade positions, and uses a wing screw rather than a wing nut. The 45 degree chamfer at the end, when the blade is in a chisel position,  let the blade be used as a knife. The sole may have too much surface area to work well on leather. Reportedly there is a plastic piece that deteriorates relatively quickly. The David is for sale at sky king rc products.

 Modelflight

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FIX PLANE (?)

German? This tentatively identified plane is perhaps the most elegant and ergonomic in form, to my eye.  It functions as a flat and chisel plane. It looks quite comfortable to grasp, and the blade is accessible from three sides for adjustment.

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SOLLINGEN BALSA PLANER

http://www.rcgroups.com/forums/showthread.php?t=183330

German. I’ve also seen this called the “Amati model ship planking razor plane“. Geometric styling.  The blade cap appears to rest on a cast stand, possibly concentrating pressure on the front edge, similar to ‘real’ planes.  The description claims this makes the blade rigid enough to plane across the grain, as well as with it. This raised area at the end of the blade cap may protect the users hand from jamming into the wing nut. The mouth on this one looks rather large for use on leather. Available from  A2Z Corp.

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MASTER AIRSCREW 4100 RAZOR PLANE 

Perhaps the most basic design imaginable. These are available from many retailers and seem to be the preferred new model among model makers. Simply designed. They use a proprietary double edge blade which is very thick at .017″ — most double edge razor blades are .oo4″-.008″. The two screws behind the blade seem to adjust depth and angle, which would make replacing the blade to the exact cut as the previous one much easier, though I wonder if the screws might damage the blade edge? The mouth looks too big to work well on leather.

Eric Alstrom adds that these are made of plastic, and “I never put it in the same class as the Little Giant.  Both for how it works and how it is made.  I’ve used it now and again for touch up, but the angle of the blade isn’t low enough to pare very effectively.  Mine came with a half dozen blades or so and I’ve only marked about half of them as used, so I haven’t used it that much.  You mention the “proprietary double edge blade” which is true they are proprietary, but my blades are only single edge.  The adjustment screws push against a flat edge.  I got mine about 20 years ago, so maybe they have changed since then.”

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LEE VALLEY RAZOR BLADE BLOCK PLANE

The Lee Valley is made in Germany, and has a rear handle that doubles for planing curved surfaces which is perpundicular to the usual planing position. The wingnut to tighten the blade is visible on the back of the handle.  The consensus among woodworkers is that  the plane is useful for basa wood, and maybe other some very soft woods, but not as a general use plane. It features three variable positions, normal use, as pictured below, as a chisel plane with the blade at the front, and curved at the heal.  Having a blade potentially positioned right on your hand seems like a poor design choice. Lee Valley advertises it as a plane to use when you don’t want to use your good plane, like on paint. The sole may have too much surface area to work well on leather.

Lee Valley, Razor block plane

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ARTU PLANE

FROM ARTU

The swiss army knife of razor blade planes with six functions. No image found, but looks the same as the plane Lee Valley is selling.  According to the manufacturer, uses special ice hardened blades at a bed angle of 27 degrees.  Some discussion about it from the Hip Pocket  Aeronautics Builders Forum.

CONCLUSION

The promise of not having to sharpen or resharpen these razor blade planes may account for their continuing appeal, as does their simple, unthreatening and lightweight nature.  Most of the packaging emphasizes their easy multi-functionality, appealing to a home repair/ hobbyist crowd. In fact, the packaging is possibly as interesting as the planes are. Even though the general consensus among users is that they don’t work nearly as well as their advertised purposes, there have been many variations of these planes over the past 50+ years and several are still in production.

Although these planes barely function on most types of wood, they are much more functional in soft materials, including leather. The combination of their curved blade bed, very low effective blade angle, the off the shelf sharpness of razor blades and small sole area prevent excessive stretching of  leather that can occur with more standard block planes.There are also many types of small planes with normal blades: block planes, miniature planes, musical instrument planes and spokeshaves, toy planes, Stanley 12-101 trim plane, Lie-Neilson model makers plane and 102 block plane, Veritas Apron plane, etc…. None that I have tried work very well on leather, primarily, I think, due to inappropriate effective blade/ bed angles, excessive friction from the soles that causes the leather to stretch, buckle or tear, and clogging of the mouth.

I find razor blade planes interesting not so much because they are exemplars of the toolmakers art, but because they are emblematic of the post-WW2 home handyman boom, the creation of suburbia, 1950’s advertising and other societal aspects. The packaging also reflects a change in tool marketing from primarily a male activity, to a family one. Tool snobs may consider these types of planes closer to toys than tools – and they may be right – but they are all tiny pieces of the total picture that inform our understanding of tool use as a fundamental human activity.

Next week : Razor Blade Planes: Tips on Using Them to Pare Leather.

Observations on Blade Angles of English Style Leather Paring Knives

“One of the most admired skills in bookbinding is the paring of leather, yet only sharp tools and confidence are required.  Confidence is gained by experience, and sharp tools by a zelous consideration and care for knives.” Arthur Johnson, The Thames and Hudson Manuel of Bookbinding, p. 89

I would add that it is also critical to pay attention to the blade angle of the knife, since it affects how the knife cuts, the angle one holds the knife at, and consequently how the leather is cut.  I’ve found that roughly a 40-50 degree angle works best for edge paring.  First, a few terms defined.  The blade angle is from an imaginary line 90 degrees to the length of the blade.  I am calling a zero degree angle one that would be straight across where the dotted line is, pictured below would be roughly a 45 degree blade angle.  The bevel angle is the amount of slope on the bevel, in the case of leather paring knives usually around 13 degrees.  The diagram below is the style of knife a right handed binder would normally use. (1)

 

I’ve found there are two main issues that determine the optimal angle of the blade– how much the blade is skewed in use and how the knife is held.  The way I hold and use an English paring style knife is outlined below, as are the reasons why I consider a 40-50 degree blade angle ideal.  

Skewing the blade in use reduces the effective cutting angle, improving the initial cutting performance and not altering edge retention.  Although the more acute the bevel angle is the sharper the blade will be, if it is too severe the cutting edge will be very fragile and quickly deteriorate.  I haven’t figured out the math, but if the bevel angle is 13 degrees, I estimate an extreme skew reduces the effective cutting angle by a degree or two, which is significant.  

I tend to use an English style paring knife in three ways when I am edge paring- first to make a series of cuts using moderate skew, then a few finishing cuts using extreme skew, and finally use the knife with no skew, almost like a spokeshave, to smooth everything out. It doesn’t seem to make too much difference if you pare across the skin, as pictured above, or push the knife away from you.

To make a long, even bevel the angle of the knife held steady by my thumb and second finger on the other side of the the knife– they slide along the surface of the paring surface. In order to pare the leather evenly, the knife must be held at a consistent angle. (2) The angle the knife is held varies with the type of leather and skill of the binder- too high of an angle takes off virtually no leather, makes it more likely to slice through the flesh side of the skin and dulls the knife tip by digging into the paring surface.  Too low an angle makes the knife difficult to control, since most of the cutting edge is engaged into the leather.  Wide knives with long bevels exaggerate this problem.  Right handed beginning parers may want to use the forefinger of left hand to push the knife along the leather.  This allows one to concentrate on using the right hand to hold the knife at a consistent angle, as illustrated below.

One reason I dislike jigs for sharpening is that the hand skills to sharpen the knife are remarkable similar to the hand skills necessary to operate the knife– if you don’t have the hand skills to hold the knife at a consistant angle to sharpen it, you are not going to be able to hold it at a consistant angle to pare leather evenly.   Some like to pare across the leather, as illustrated below, and some like to pare up the side of the leather, starting the cut with the heel of the knife rather than the tip. Since lithographic stones are now extinct, I prefer paring on a piece of glass and saving stones for printers wishing to experience printing on a real stone.  There is no reason to pare on a litho stone other than tradition, and I suspect the only reason they were historically used is that they were a cheaper flat surface than glass, marble or granite

 

 

 

 

 

 

 

 

 

 

 

 

After a first cut is made, a second (and possibly third or fourth, depending on how long of a bevel is desired) is made by holding the knife at progressively  lower angles.  The depth of the cut can be judged by changes in the color of the leather or folding the leather in half, which doubles any errors.    If the leather is disturbed to check the progress, it is imperative that any stray bits be cleaned from under the skin, otherwise the knife will cut through these thicker layers.

As the leather becomes thinner, it becomes weaker, so I adopt the second knife position.  I skew the knife towards a more extreme angle and press down harder, which creates a lower effective bevel angle. This helps prevent tearing the leather.  It is much easier to take the leather off in long even strips with the first cuts, rather than try to correct mistakes later on.  If there are many irregularities, sometimes it is easier to use a spokeshave to even things out.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After the edge is pared to the length and thinness desired, I rotate the knife into the third position, so that it is not skewed, and push it forward to even the previous cuts out.  This is almost more of a scraping action than a paring cut, and is meant to smooth out irregularities left from the previous cuts, not remove a lot of skin. The angle of the camera in the illustration seems to exaggerate angle that the knife is being held- in reality it is almost parallel to the skin. Again, a spokeshave could do this as well. The cutting edge of this knife is one inch, which is slightly larger than most turnins. Most of the time 7/8″ is a reasonable turn in width–compromising between giving a little extra room in case the leather is torn, and conserving leather.  One unintentional consequence of the acidic nature of some leathers is that they rapidly stain the pastedown, making it possible to observe in detail the pattern of trimming and size of turnins.  I admire the judgement (and frugality!) of some binders, capable of covering the book so economically that only a millimeter of two of leather extends under the pastedown in various places.

 

 

 

 

 

 

 

 

 

 

 

 

 

A roughly 45 degree angle seems to be the most comfortable in all three of the ways I hold the knife.  I have a set of knives that I use when teaching which consist of 22.5, 45, and 67.5 degrees, in order to compare what is most comfortable for each individual, and most opt for a roughly 45 degree angle. Another consideration is the angle of the wrist when using the knife– I’ve found around 40-50 to be most comfortable.  Keeping the angle of your wrist comfortable is important if you do a lot of production work, to avoid carpel tunnel syndrome.  Any numbness or tingling sensation is possibly a very serious problem, and medical attention should be sought.  Choosing a good quality knife, keeping it well stropped and sharp will also reduce the force needed to pare leather, reducing strain on the hand and wrist.  Finally, a 45 degree blade angle is much easier to sharpen than a 67.5 degree angle for two reasons– it is easier to get even pressure across the entire width of the bevel (especially the tip), and there is less metal to remove, so the sharpening is more rapid.  Paring leather is not difficult, as Johnson pointed out, it just takes some practice with a sharp knife, and an awareness of the blade angle.

 

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NOTES

1. As a left handed binder pointed out to me, simply changing the direction of paring allows a right hander to use a left handed knife, or vice versa.  Below I am comfortably using a left handed knife, holding the leather at the top and paring towards myself.  

 

2.  Some find it more comfortable to hold a knife with a handle.  In this case, it is sometimes necessary to hold the handle area of the knife off the paring surface in order to achieve a low angle.  This illustration also demonstrates side to side paring.