Introduction
Although I am sure that you all understand the concept of friction, many of you are probably not familiar with the term “lubricity”. Lubrication is defined in the Merriam-Webster dictionary as: ability to reduce friction. You can also think of it as a lubrication ability (for example, oil, water, Teflon, etc.) to reduce friction between two objects. Just for your information, the study of lubricity is part of the broader science of tribology — the study of interacting surfaces in relative motion. Although this information can be very interesting for some and boring for others, it is important for anyone who wants to truly understand the sharpening and polishing of the blades. Therefore, if you belong to this particular group or want to read it.
Lubrication and pursuit of the perfect edge
Since the pursuit of a perfect blade is our agenda here, let's apply the principles of lubricity for honing and gouging thin blades. Suppose we have a flat surface covered with a liquid containing particles that are harder than steel. Suppose further that we move a steel blade along this surface, using only the weight of the blade itself for the downward pressure. As the lubricity of the fluid increases, the friction between the abrasive surface and the steel in contact with this surface decreases. This reduction in friction reduces the ability of the abrasive to remove metal. The extent to which material for removing abrasives is often referred to as the “cutting force” of an abrasive.
Since cutting power is what we all want from our abrasive surfaces, we should always maintain minimal lubricity, right? Well, it depends. Have you ever tried to sharpen a blade on a dry water stone? How about a dry DMT diamond plate? If you have, you have already experienced the effects of very low lubricity - some metal is removed (not always where you want), and the stone or slab is soon clogged with worn metal fragments. This makes the abrasive surface unmatched cutter - leaving some spots that cut sharply, and others, where the cutting force essentially does not exist. In addition, this lack of lubricity also makes a very rough edge - something that you can see under a microscope and, of course, feel against your skin.
The role of lubricants in creating better edges
It is for these reasons that we usually use a lubricant (which increases lubricity) when honing. Lubricants reduce friction between the abrasive and the blade, reducing cutting power, but producing a more consistent cut and a smoother edge. The lubricant also helps to remove the metal (and “waste” abrasive particles) removed by the abrasive material, which helps prevent the “clogging” of the honing or trimming surface that occurs when the surface is too dry. Finally, the use of grease prolongs the life of the abrasive surface.
Proper lubrication is important when you use an abrasive, which is significantly more difficult than a piece that you are trying to sharpen or polish - and they do not bring more effort than a diamond. Diamonds, natural or synthetic, are the hardest substance on earth. Hardness is not the same as strength - you can take a hammer and easily break a wedding ring (PLEASE do not try this at home); it simply means that when moved with a softer material (which is everything else on earth, except for another diamond) with sufficient pressure, the diamond is cut into this material and removes part of it. The depth and shape of this cut and the amount of material removed is imputed to the shape of the diamond, the pressure applied to the workpiece against the diamond, and last but not least, the lubricity of the solution standing between it and the softer material.
Water is the most common and inexpensive lubricant. It also has an extremely low lubricity and viscosity (a measure of the resistance of a fluid under load, often called “thickness”), which is one of the reasons why it is not used to lubricate moving parts in a car and trucks. However, he has qualities that are very desirable when honing a razor, thin knife or tool. It is abundant and inexpensive, easy to clean and performs a fair job of transferring worn metal and abrasive material, providing a more consistent cut and extending the life of abrasive materials. It also helps produce a less jagged edge than you could produce using a dry surface, although not as smooth as you would get with excellent lubrication.
The princess and the pea - like something very small can be very annoying
Despite the fact that this is the main topic of this article, I'm going to talk a little about lubricity in order to talk about micron-free abrasive particles and especially sub-micron levels. You will have to trust me that this short leak is important and that I will return to this topic in a few paragraphs. First, let's quickly try to wrap the brain around the concept of a micron-sized particle. To put microns in perspective, you might think that the period at the end of this sentence is about 400 microns in diameter; and that one micron is equal to about 1/300 of the diameter of a strand of a human hair. The particles of the submicron level are obviously even smaller — they are so small that electron microscopes must see them.
Despite this tiny size, there is a general complaint about suspensions that use diamonds less than one micron in size - they leave too harsh or "toothed" edge. It seems somewhat counterintuitive when dealing with such small particles, but this is true. This effect leads to the fact that many mountain masters (experts in the field of creating perfect edges) use chromium oxide (a substance softer than diamond), glued with slings after using diamond slurry sprayers. There is something like this in the reasoning: “Diamonds are more solid and then they will cut deeper and rougher scratches than chromium oxide, therefore honing on chromium oxide is necessary for“ edges ”. This is only partially correct and is usually the result of improper use of a diamond of the wrong type.
Synthetic Single Crystal Diamonds (SMD)
Most diamond slurry formulas sold for sharpening small blades (including those sold by market leaders, HandAmerican) rely on synthetic single crystal diamonds (SMD) as an abrasive.
Popular because of its extremely low cost and high durability, SMD diamond suspensions are an excellent choice for removing material at an early stage, but have some inherent problems that make it a poor choice for final finishing. These problems include, above all, the shape of the particle itself. It is “blocky” with very sharp, but very small cutting edges. SMD suspensions also suffer from problems with the shape of particles, such as the presence of needle-like "chips" and long and flat "lamellar structures." These “strains”, which often pass by equipment and testing procedures of the highest quality in size (PSD), lead to a significantly high “scratch” of the SMD — tiny fragments of damage to the blade surface. These scratches are not visible when zoomed under a conventional microscope (you need an electron microscope to view them), but they can be perceived on the edge, which is used for shaving as “severe”.
For these reasons, SMD diamond suspensions are not the first choice of manufacturers who need to produce the best finishes. That is why I do not recommend the use of SMD diamonds in submicron-level suspensions used for final finishing / polishing. Although it is beyond the scope of this article to delve into the subject of the morphology of diamonds, I felt I should mention this because on the website of the current market leader HandAmerican there is a claim that single crystal diamonds are more suitable because they will leave less “toothed” edge ”than polycrystalline diamonds (http://www.handamerican.com/compoundnotes.html#Particle%20Shape). It is not true. In fact, there are many studies that reach exactly the opposite conclusion.
Synthetic Polycrystalline Diamonds (SPD)
Synthetic polycrystalline diamonds (SPDs) possess many attributes of their single-crystal cousins (especially hardness), but their structure, which is formed by controlled detonation of explosives, is very different. Each tiny SPD particle contains even smaller “microcrystallites” that numerous planets are sharpened in different crystallographic directions every 10–50 nm (the measure is much less than microns) - regardless of the particle size distribution of the original particle. The hardness of each individual microcrystallite can be compared with the hardness of synthetic single-crystal diamond. Due to the larger number of cutting edges and a larger surface area that are simultaneously in contact with the workpiece, SPD-based suspensions remove more metal than SMD suspensions, and are much less likely to cause underground metal damage. But all these good quantities come at a price - polycrystalline diamonds cost much more than single-crystal preparations.
Re-lubrication
Earlier in this article I described the characteristic problems of using abrasives with little lubrication or lack of lubrication - uncoordinated cutting, sharp cutting and clogging of the abrasive surface. Considering what we learned about “wandering” particles in SMD suspensions, it is not surprising that these problems will be exacerbated by using a solution with very low lubricity, especially when you use particles with an inherent tender for “gouge”? Is there a scratch in the absence of lubricant deterioration?
Most diamond suspension dispensers, such as products manufactured by HandAmerican (I received a 4 ounce 25.5 µm single crystal suspension spray bottle for $ 34.95 from chefsknivestogo.com), use media (solution in which abrasive particles are suspended) with very low lubricity - mainly depends on deionized water to reduce friction. You can see it the way the product is sprayed (sprays), creating an extremely thin mist very similar to tap water (in my opinion, too thin, at a distance of 5 "from the stem it produces a rough circle 8" in diameter - leaving more on the table slurry than on the strand. Spraying closer, the suspension is too “concentrated” in one place.). It also dries quickly with 100% solid wool from the melt, which also indicates a primary dependence on water as a lubricant. You can also feel almost complete lack of viscosity when “drawing out” or friction, perceived when applying the blade to hard wool treated with HandAmerican. And since it is often used in dry form (which may or may not be intended to be used - no instructions are not attached), friction increases - at least measure until the abrasive metal starts to clog the surface.
Therefore, after I put the razor on the hard wool sprayed with this product, used in a wet or dry condition, I found that it was necessary to use roasting on chromium oxide before use - since the blade dropped by spraying does not tend to leave a harsh edge. If you work with knives, you probably need a sharper edge — especially at submicron levels, since microscopic scratches can provide better cutting action — you can just pay less for it.
How to get the maximum edge for less money
We have customers around the world who hope to place the very best edges on razors, knives and fine tools. In response to these needs, Little StropperTM has developed products that use less expensive synthetic single-crystal diamonds in our 1 and 2 micron suspensions (where a higher scratching speed is less and may even be desirable), and more expensive synthetic polycrystalline diamonds (SPD) in our suspensions .50 microns and 25 microns. Since submicron-level suspensions are usually used for finishing and polishing, we thought that using synthetic polycrystalline diamonds with their much lower scratch speeds was worth the extra cost. In addition, in all our formulas, we use significantly higher levels of water-soluble lubricants than you will find in leading brands. This way you will feel less friction when using our products, but you will get a better and smoother advantage. You will also use less product as we add special ingredients designed to keep the lesion surface moist for long periods of time.
One more thing you appreciate is our prices. Even our SPD formulas, which use a much more expensive diamond than our SMD products, are rated lower than those of leading brands. Depending on the formulation used, our products per ounce per ounce cost 35% less than competitive products. We announce the following products that will be available for sale in January 2011:
- · 2 microns Premium Synthetic Monocrystalline Diamond Slurry Spray (size 2 ounces)
- · 1 micron Premium Synthetic Monocrystalline Diamond Slurry Spray (size 2 ounces)
- · 50 microns Premium Synthetic Polycrystalline Diamond Slurry Spray (size 2 ounces)
- · 25 microns premium synthetic polycrystalline diamond syringe (2 oz)
- · SlurryLube Tm - extender and lubricant for diamond suspension with an economical cost (size 2 ounces)
Beware of competitors carrying carriages
A word to the wise - be careful with the diamond suspension manufacturers who tried to distract you from the price of their product, focusing on the number of carats of diamonds in a bottle. “Packing” more and more diamond powder into a slurry bottle, while, of course, provides ratione for charging a high price, is unlikely to improve product performance. Additional diamond particles are simply lost. Our products are formulated with an emphasis on performance and results, not on carat weight. So you end up paying for efficiency, not from powdered diamond.
Conclusion
In this article I used quite a bit of science and jargon - I apologize for this and try to minimize it. But most of you reading this (and thank you for coming so far behind me) are not tribologists. You are people who, like me, need a smooth shave every day. You want knives that are cut clean, without slipping. You want chisels and other tools that will safely remove material without “skipping” surfaces or damaging your creations. You also want to spend less time and money there.
Recommendations:
Tumavitch, Nicholas J., Evolution of Diamond for finishing optical components. Recent developments in the production of synthetic diamond abrasives have responded with a variety of varieties suitable for optical finishing.
