In the 21st century, bookbinders are understandably nervous concerning the continued availability of essential machinery and replacement parts. Many of the board shears and guillotines we use on a daily basis are more than a hundred years old. This equipment not only needs to be maintained, but periodically their blades need to be resharpened or replaced. The last New York City grinding service, Ace, moved to New Jersey a number of years ago, priced out of Soho.
I support Ace by using their services. I also collect and preserve bits of history associated with these types of industries, such as this desk blotter ephemera I scored over the past weekend. This is the second bookbinding related desk blotter I’ve found in the past month, a little unusual, though synchronous finds are not uncommon in dedicated flea market and antique mall exploration.
The Wapakoneta Co. was sold in 2009, but is still making knives and industrial cutting products. But as the numbers of newspapers, books, and other paper based products continues to shrink, what will happen to these vital ancillary trades — like board shear blade making and resharpening — that hand binders and conservation labs rely on?
One of the most common mistakes in sharpening is to allow your stone or film to glaze over. This significantly increases sharpening time, since the knife is not abraded by the grit, but is burnished against embedded steel. Not using enough lubricant is a common reason for this, as is not regularly cleaning your substrate. Depending on the size of the grit, either a microfiber rag or a white vinyl eraser works best.
My sharpening setup, above, consists of a bright swing arm lamp mounted directly above a cork faced workbench (PSA cork shelf liner), a microfiber rag, a large squeeze bottle of water, and the Peachey Sharpening System. I find it more comfortable to sharpen at a lower height, around 34 inches, than my regular bookbinding workbench. Many hundreds of knives have been sharpened here!
The microfiber rag is perfect for cleaning larger grit 3M micro-finishing film, from 80 to around 15 microns. This rag was white when I purchased it, a testament to how well it picks up and retains small metal particles. I also use it to clean off the knife between grits in order to examine the scratch patterns.
For 5 micron and smaller grits, a white vinyl eraser works wonders. Pictured above is the neon lime green 1 micron film, which glazes quite easily. Using the eraser on coarser grits eats it up too quickly.
Of course, over time, the abrasive will wear to the point nothing much happens, and you will need to replace it. I can usually sharpen ten knives or so on one piece of 2 x 11 inch film.
By using plenty of water as a lubricant, and cleaning the film after each use, the effective working life of finishing film will be prolonged.
A meter was originally intended to be one ten-millionth of the distance from the North Pole to the South Pole where it passed through Paris. The Measure of All Things is a facinating book by Ken Adler which documents this feat of triangulation — in the middle of the French revolution, no less — and also explores how the defined length of a meter has since changed. A millionth of a meter is a micron. As a point of reference, a hair on your head is about 40 microns wide. A thousandth of a micron is a nanometer. Yes, I’ve been thinking small!
Typically, I hand sharpen following a grit progression of 80, 40, 15, 5, micron on 3M microfinishng films with water as a lubricant, strop with a .5 micron Chromium Oxide (CrO2), honing compound on the flesh side of a horse butt strop, then finish stropping on naked flesh side kangaroo. Don’t get me wrong, this works quite well. And there are many other ways to sharpen a knife.
Inspired by some other sharpening approaches, two aspects of my routine seemed to need a little tweaking. First, I eliminated the large jump between 5 and .5 micron, and found some finer grits for a final stropping. Adding a 1 and .3 micron 3M PSA finishing film filled in the gap nicely during sharpening. And a final stropping with a .1 micron Poly Crystalline Diamond (PCD) diamond on polyester leather has dialed up the sharpness to eleven.
PCD or Cubic Boron Nitride (CBN) compounds smaller than .25 micron don’t work well on real leather for two reasons: the expensive spray soaks into the leather and disappears alarmingly fast, and the natural abrasiveness of the leather itself is sometimes coarser than the spray.
One solution is to use a polyester leather, which is similar to “nanocloth”, a term Ken Swartz has coined and a great product he sells. Polyester leather is made from an ultra micro fiber that holds sub-micron sprays incredibly well, is very thin so the cutting edge does not become rounded, and is extraordinarily durable. Human hair is roughly 20 denier, but this ultra micro fiber is .04 denier. Denier is the mass in grams of 9000 meters of a given fiber. It is difficult to imagine how small and light this fiber is: 9 kilometers (over 5.5 miles) of it only weights .04 grams! All of these tiny little fibers hold the diamond particles loosely while allowing them to move around a bit, exposing new sharp edges. I think this is why they last so long.
In other words, this polyester leather is a perfect substrate for .25 micron and smaller sized sprays. I’ve experimented with the .25 micron (~64,000 grit, 250 nanometer), .1 micron ( ~160,000 grit, 100 nanometer), and .025 micron ( ~640,000 grit, 25 nanometer). These are available in PCD and CBN. The diamond seems to stay sharp longer (because of the shape and hardness?), cuts a bit faster, though is more expensive. The .25 micron is pretty close to the .5 micron CrO2 I usually use, and though it does cut quicker and lasts longer, it seems an unnecessary expense. Waxy pastes don’t apply or stick well to polyester leather.
In terms of initial cutting performance and cutting edge longevity, I can’t really tell much, if any, difference between blades stropped with the .1 micron or .025 micron. Even so, the idea of a one fortieth of a micron edge does have an almost irrational appeal, but is it just a placebo effect? Also theoretically, the smaller the grit progression in your sharpening sequence, the finer the cutting edge, and the faster you get there. But everyone has to decide for themselves if the trade off in time spent sharpening is worth the final result.
Diamond compounds are expensive, but once they are loaded onto the polyester leather they last for a long time. In my experiments, I’ve used a single polyester leather strop loaded with .1 micron for over 100 knives without recharging, and it isn’t dead yet.
I’m a convert to this new sequence. It really doesn’t take much additional time, and the resulting edge is better. All the knives I make now follow a 80, 40, 15, 5, 1, .3 micron sharpening sequence, and a .1 micron stropping. When I am paring leather for my own projects, I do a two stage stropping sequence to keep the knife sharp. First, a .5 micron CrO2 on horse butt followed by .1 micron PCD on polyester leather. Once the edge becomes too obtuse, then it is time to resharpen.
Choose your poison and treat yourself to a sharpest knife you’ve ever experienced for this Christmas!
The Superstrop has a half inch thick cast acrylic core, which is the flattest plastic available, as well as being very dimensionally stable. Flesh side horse butt is mounted on one side and flesh side polyester ultra-microfiber leather on the other. The strop has a nice heft, about 14 ounces, so it doesn’t move around on the bench while stropping. The polyester leather comes loaded with .1 micron Poly Crystalline Diamond (PCD) compound, which should last a very long time. Sub-micron diamond replacement sprays are readily available. Replacement PSA horse butt and PSA Polyester leather is also available. When working, I like to use the .5 micron Chromium Oxide (CrO2) honing compound on the horse butt, wipe off the knife to prevent grit contamination, then finish with the .1 micron PCD. Also available with polyester leather on both sides, loaded with .1 and .025 micron PCD.