It's concert night. Tchaikovsky looms before you. As curtain time approaches you feel the urge for just a little more security. A little work on the reeds might do it. A few quick scrapes and... your reed lies lifeless in your hand. Camel fodder. Your murderous glare falls on the prime suspect... the reed knife!
Yesterday the knife worked fine but now it feels like a saw even after using your finest stones. In the drawer sit two new knives for which you paid a week's grocery money. Neither one works. The situation has become so desperate you have even tried making your own knives. But the best steels, recommended by top knife makers, just don't work. Is there no hope?
Well, no there isn't. At least not for tonight. However, the future may be a little brighter. For the past two years reed knife research has been underway and some significant results have surfaced.
I am a horn player, recently transformed into a mechanical engineer. After several years of acquaintance with jean Landa, principal oboe with the Calgary Philharmonic, we decided to join forces and pursue a research project at the University of Calgary which would focus on the metallurgy of reed knives. The project has produced a wealth of information and the success has been such that we are able to begin the production of reed knives. The combination of musician and engineer has resulted in the development of metallurgical theory specific to reed knives which goes beyond the standard knowledge of most metallurgists and heat treaters.
Let me address some specific issues: Why is it that so many reed knives are inconsistent from week to week, or even from day to day? Why do the finest stones sometimes fail to produce a correspondingly fine burr? And for those who are lost in their own search for the perfect knife, why do the best steels money can buy often result in terrible reed knives?
These three questions can be answered in one word... microstructure. For the double reed virtuoso who is not also a metallurgist this term requires some explanation.
Microstructure is the microscopic fabric of a material, in this case, steel. A picture of the microstructure of a high quality steel is shown in Figure #1. This is a very good machine steel, with a hardness of Rockwell C 59, polished to a mirror finish, etched with acid and magnified one thousand times. This is the type of steel used to make stamping dies for the production of hundreds of thousands of pieces before replacement is necessary. This is also a steel which makes very poor, in fact, unusable reed knives.
Note the large angular particles appearing throughout the photograph. These are called precipitates or carbides. It is the size, shape, chemical composition and distribution of these carbides which will determine how or even if, a reed knife will function.
In order to understand these carbides from a purely physical point of view, imagine them to be blocks of wood. If you were to hold onto a wooden croquet ball with one hand while I attempted to pull the ball out of your hand by means of a string attached to the ball, it would be difficult to remove the ball from your grasp. However, if we do the same thing with a wooden cube, I will have no trouble extracting it. This is because the force of my pulling is concentrated on the corners of the cube rather than spread evenly, as with the ball. Similarly, if we have one of the angular carbides shown in Figure #1 on the scraping edge of the knife, the act of scraping will easily knock the carbide out of the burr. This will leave a hole in the burr as in Figure #2. Shown here is a picture taken with an electron microscope of the burr of a knife made from the same material as Figure #1. You are looking down onto the edge of the knife with the burr edge running from lower left to upper right as shown by the arrows.
Now, suppose this hole is larger than the grain size of your finest honing stone. The fineness of the edge will then be determined by the size of the carbides falling out rather than by the stone. Your finest stone will have no effect!
Unfortunately, many high quality steels have this undesirable component of large angular carbides. This is acceptable and even desirable for uses which do not require such delicate and abrasive work as reed making. In fact, it is often impossible to achieve a microstructure other than that shown in Figure #1. As a result, randomly searching through expensive high quality steels can be a costly waste of time without the necessary theoretical background.
So much for the physical considerations of carbide size and shape. What about chemical composition? In a good knife most of the carbides are harder than the surrounding material. They can help to scrape away the abrasive reed material if they don't fall out. But some carbide-like particles will be softer than the surrounding material. It is important to have these softer particles to keep the steel from becoming so brittle that it won't take a burr. Commercial heat treaters will often suggest that a knife be immersed in liquid nitrogen to harden all of these softer particles. This is not appropriate for a reed knife, although it is a useful technique for other applications.
Finally, let's look at the distribution of the carbides throughout the knife. Carbides form while the steel is being tempered. The way in which steel is tempered commercially usually results in clusters of carbides forming unevenly throughout the steel. Should you get a cluster of large angular carbides on the edge of your knife, it won't work until you have honed that section away. This may take a few strokes, or for a large cluster, it may not be possible at all. The result is inconsistent performance of the knife.
Now put this all together and look again at that piece of steel lying in your hand. Probably the reason it feels like a saw is that the carbides are too large to permit the fineness of burr you desire. The inconsistency from day to day is often due to the uneven distribution of the carbides throughout the steel. Lack of control of the microstructure formation can easily lead to entire batches of knives that just don't work. And finally, beware of random searches through the myriad of available steels. Armed with the best steels and the most well-meaning advice from your neighborhood treater, you will probably have very limited success, if any at all, due to the very special and precise treatments required for something as unique as a reed knife.
As for the knives which we are now putting into production, Figure number 3 is a picture of the microstructure resulting from the steel selection and heat treatment developed to the present time. The carbides are small, round and evenly distributed giving a knife which will take on a very fine and consistent burr. This means the knife will behave consistently throughout its life and will respond to the finest sharpening stones.
An interesting aspect of gaining control of the microstructure as we have done, is that it allows a range of knives to be produced which offer a selection of performance characteristics. Therefore, we are able to offer a knife tailored to the specific preferences of the individual.
We are now producing these reed knives under the name of "LANDWELL." Should you wish to try one of our three available models (stiff, medium and flexible, all double hollow ground) or if you have any questions concerning knives in general, please contact me at the address given below.
Meanwhile, as curtain time approaches, grab your stone, remove a good bit of metal, and hope for a good spot. Good luck.
For more information contact:
Daryl Caswell
c/o Landwell Reed Knives
3120 Breen Cr. N.W.
Calgary, Alberta, Canada T2L 1S7
Phone 403-282-7093
About the writer...
Daryl Caswell is a mechanical engineering graduate specializing in material science. His strong interest in developing engineering solutions to arts related problems has most recently resulted in a prize winning entry at the 1986 International Metallographic Exhibit held in Boston, Mass. A past member of the Calgary Philharmonic horn section, Daryl continues to play and teach as well as pursuing the many opportunities for combining art and engineering.