“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.
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.
5 Replies to “Observations on Blade Angles of English Style Leather Paring Knives”
I think your analysis of blade angle in the English paring knife might be expanded in light of one major factor: traditionally, the usual way of paring with it was to pare the right edge of the leather (not the far edge or left edge) using the heel (not the tip) of the blade in a push directly away from the body. This is the way I was taught. Some English manuals show a left-to-right movement with the tip, but more show the push with the heel. The roughly 45 degree skew is to give the optimum angle when heel-paring, not when tip-paring.
Some of my older (probably pre-WWII) American-made knives have an angle closer to 30 degrees than 45, and I suspect that these were intended for paring left-to-right with the tip; I find the more extreme skew, in your useful terminology, makes tip-paring easier. In freehand sharpening for heel-paring a slight rounding of the heel quickly develops, which means that in practice this too is using a more extreme skew at the cutting area. A slight rounding is deliberately created at the tip to reduce the tip’s tendancy to catch and slit rucked-up areas of the skin. Eventually the rounded areas at heel and tip will grow and meet, giving a curved edge similar to the standard German paring knife. With a knife like this an experienced parer can use up the entire edge by slightly altering the angle of the hand.
There is no objection to an extreme skew per se, but one problem with it is that the cut tends to morph from a “slanted chop” moving directly (but at an angle) into the leather, into a sliding saw-like slice (like slicing bread or steak), especially if the knife is getting a bit dull. The slice is a way to get a dull knife to cut after a fashion, but it lacks control and turns what should be a single smooth motion from one end of the leather to the other into a series of short reciprocating strokes. One of the clues that Laura Young never learned to sharpen a knife is her description of hand paring, which (IIRC) describes a slicing cut after giving instructions on knife-sharpening which would be certain to result in a dull edge. Then she recommends using a thousand-dollar Fortuna paring machine.
Why push? I don’t know, unless it became a habit when over-all paring was done with the French knife. I do find that in some spots it is easier to push-pare, but in others it is easier to use the tip, and I now make more use of the tip than the heel. The biggest advantage of using the tip is that the left hand can hold the skin directly behind the spot being pared, which stretches the skin and avoids difficulties with soft, flanky leather rucked up in front of the edge. But push-paring with the heel works well once it is mastered, especially in firm areas; and if both the tip and the heel are used, the sharpness of the entire edge can be used up: one doesn’t have to resharpen when half the edge is still sharp.
In teaching paring the push-stroke has an additional advantage: it makes it easy to explain the three directions of manipulation of blade angle, on the analogy of the directions of movement in an airplane: roll, pitch, and yaw. When pushing a paring knife, the axis of movement is the same as the center line of the knife. Roll is rotation around the axis of movement; yaw is rotation around a vertical axis at right angles to the line of movement; and pitch is rotation around a horizontal axis at right angles to the direction of movement. The same changes in angle are made when tip-paring, but comprehending them is made harder because the direction of movement of the edge is at right angles to the axis of the knife.
My experience has been not only that there is a great difference in harshness between glass, marble, and litho stones, but that the main types of litho stones have differences in harshness. One type has a tinge of creamy pale-tan to it, and this type is definitely the easiest paring surface for the knife-edge. Another type of litho stone has a slight cold gray tinge and a bit more tooth; this is definitely a bit harsher. I have some well-worn pieces of white marble that I have used at times, not as good as litho stone, and a highly-polished stone trivet that I take to workshops where there will be paring, also not as good as litho stone. If I had any choice I would prefer any of these to glass, which seems harshest to me; though one old trade bindery I visited a few times in the middle ’80s had a glass paring surface that I would quite like to have: it was trapezoidal, perhaps three inches thick, and very strange looking until I realized that it was an armored glass front window from a World War II fighter plane. Possibly I have noticed the differences more than you have because I do most of my paring with old Barnsley knives, which are rather soft (around rC 55) but also quick to resharpen.
I’ve noticed that English binders who trained before the late 1960- mid 1970’s seem to do what you call heal paring, which is a good term. But specifically Pickwoad and Clarkson, who trained with Roger Powell around this time, demonstrated tip paring when I have seen them pare. Also the new style German knife, with it’s long flexible blade can only be used heal paring. I also have an older, 19th C. German knife that was actually made a few blocks from where I now sit, in Cooper Square, NYC, whose angle is closer 52 degrees, yet it is as wide as a contemporary French knife.
Any old timers know why the switch to the tip?
Thank you so much for this tutorial. I am an amateur binder and i have been binding mostly with leather, but without the means or know how to pare the leather properly.
I am a purse maker and i use leather a lot. I recently purchased a hide that is thicker than I should have bought. Now I have the ordeal of edge skiving. I have been looking for a paring knife to do this. Can you give me some adivse as to where I can get a nice English knife? I can’t find a Vergez-Blanchard which so many leather craftsmen are using. So I have to find an alternate knife. Also, what is a spokeshave?
Yes, you can purchase a very good quality english style knife from me, link to “Tool Catalog” is on the right. Search in the box for “spokeshave” and you will find a history of them, as well as pictures.