What determines the best sharpening angle? The answer is one that plagues knife neophytes and old hands alike.
“The best angle of sharpening is one of those very intriguing topics that many have explored but most have come up with different answers,” states Jake Broce, online marketing coordinator for A.G. Russell Knives. Agrees Kyle Crawford, brand manager for Work Sharp, “The answer is often different for everyone.”
He says the two keys are knife type/use and edge retention/maintenance. In fact, all of our story sources cited the intended use of the knife as a deciding factor. For tough chores such as chopping or batoning, a wider angle is best. “Generally, the wider the angle of edge, the more steel is behind it, which increases the edge’s toughness,” Broce observes. “For kitchen knives that see light-duty cutting food on cutting boards, or a task-specific hunting knife like a camping knife, a low angle is ideal,” counters Crawford. By “low” he means an edge angle between 15 and 20 degrees.
Edge angle also affects edge retention. “If you sharpen your heavy-use EDC knife to a low angle such as 15 degrees, it will be incredibly sharp,” Crawford says, “but the trade-off you are making is edge retention and durability.” Conversely, he adds, if you sharpen at a wider angle, such as 25 degrees, the edge will still be very sharp but you gain improved edge retention and, thus, eliminate the need for more frequent maintenance.
However, Kendra Tobler, marketing communications manager for Benchmade Knife Co., indicates grades of blade steel also factor in as well. “A harder steel with higher yield strength can be ground to a small included angle with less worry about rolling or deforming the edge,” she says. “Conventionally cast steels with large carbides are better suited to larger included angles.” This is done so for edge durability.
A prime example of Tobler’s point is Benchmade’s 15017-1 Hidden Canyon Hunter, a compact drop-point fixed blade in premium CPM S90V stainless steel well known for its extreme edge-holding ability. Benchmade uses its SelectEdge 14-degree included edge on the knife. It is ground thinner because S90V is a high-yield-strength steel that can retain its strength with a thinner edge without deforming or chipping. Blade thickness is a factor as well. “Thin blades are much easier to sharpen to low edge angles than thick knives,” Crawford states. “The thicker the blade, the more material you will have to remove to create a low edge angle.” And it usually takes time to thin down a thick blade. As he warns, “If you choose to sharpen a low edge angle onto a thick blade, be prepared to be patient.”
Sharpening To Steel Grade
“Modern super steels have really changed the game for low angles and edge retention,” Crawford says. By this he means
blades of lower quality steel are prone to low edge retention as well as edge deformation and damage incurred from use. Higher quality steels have the high yield strength that enables them to be sharpened with lower edge angles, resist deformation and damage, and have higher edge retention overall. Crawford specifically cites CPM S45VN and CPM 154 as types of high-yield stainless steels. For lesser grades of steel, opt for a wider angle to save you from having to deal with damaged edges and/or frequent edge maintenance. Any steel designated as CPM (manufactured by Crucible Industries) or any other high end/high-performance steel can be taken down to lower edge angles for enhanced performance. Such steels include M4, 20CV, S30V, S35VN, S45VN, S60V, S90V, S110V, CRU-WEAR® and the CPM version of D2.
Lesser grades of steel that should not be taken down to acute angles mostly are found on entry-level to mid-grade factory knives, and some higher-end non-CPM steels found in high-end factory knives. Such stainless steels would include 440A, AUS-8, 8Cr13MoV, 1.4116 and VG-10. The high-end non-CPM stainless steels would be 154CM, ATS-34 and 440C. Also, any grade of carbon (non-stainless) steel should be treated like this as well. Examples would be 1095, 5160, D2, O1, A2 and so forth. If the steel’s specs do not state that it is a CPM steel, avoid applying acute edge angles and stick with wider ones to be safe.
Consequently, it is very important to educate yourself on the different grades of steel and their performance characteristics and edge retention qualities. Such information will further help you understand how the steel type will perform and how maintenance should be handled.
Sharpening To Blade Grind
The many different types of blade grinds are largely influenced by the knife’s intended use. As Tobler notes, “The bevel grind and the sharpening angle should complement each other.” For instance, hollow-ground blades have thinner edges. “This complements a small included angle,” she states. “A convex edge provides plenty of material behind the edge for strength and support and works well with a larger included angle.” Adds Broce, “The blade grind determines how much steel is behind the edge. More steel behind the edge improves edge stability, whereas less material behind the edge can improve the pass-through” of the material being cut.
Crawford takes a different tack. “The edge angle is seldom impacted by the blade grind,” he says. “Be mindful the sharpener you are using may not be able to replicate the blade grind. [Author’s note: Hollow grinds are converted to flat grinds when using a stone, or too convex grinds when sharpening on a flexible abrasive belt.] But for most of us, sharpness is the goal, not maintaining the exact factory grind type.”
Know The Use
“The required cutting task affects the angle,” Broce says. “Chopping requires good edge stability, so an increased edge angle is necessary.” He also explains that finer chores such as slicing and dicing work better with more acute angles due to the precision cutting. “Whittling introduces more variables than normal knife use,” he states. In other words, whittling exerts a lateral force on the blade and, therefore, the cutting edge. “Generally, you want a thicker blade stock with a thin edge [on a whittling knife],” he sums up. Agrees Tobler, “Smaller angles, like our SelectEdge, work best for finer, delicate slicing cuts.” The primary goal for Benchmade’s 14-degree SelectEdge is for field dressing, and the acute-angle edge slices through thicker hide and meat almost effortlessly.
Knives come with a standard edge from the factory, around 22 degrees inclusive. The edge is sharp and durable, and a good middle-of-the-road angle that is a good balance between durability and cutting ease. Some users are harder on a knife and require the larger edge angle. Nonetheless, with task-specific knives of high-yield-strength steels for hunting/field dressing, you may opt for a more acute edge angle, anywhere between 15 and 20 degrees.
Establishing The Sharpening Angle
How should you go about establishing the edge angle when you sharpen? A safe bet is to invest in a sharpener that sets and maintains the edge angle for you—all you have to do is set the sharpener to the desired angle.
“Angle guides are tried and true and solve one of the biggest sharpening challenges—establish the angle and be consistent,” Crawford says. Cautions Broce, “The first time you use [a guide kit] on your knife will usually take the longest, as your edge angle adjusts to the way you use the sharpener.” The angle guide kits subtract the science of maintaining a consistent angle, so all you need do is concentrate on getting the edge sharp. The kits have been a game-changer for consumers who struggle with freehand sharpening on a bench stone.
Another good tip, regardless of which sharpener you use, is the tried-and-true black marker trick. Using a permanent black marker with a wider chisel tip, color the edge bevel on both sides of the blade. The goal is to sharpen the blade,
removing the black marker ink from both sides. When you accomplish this, your edge angle is correct and you should have a sharp blade.
“The goal is to remove all of the ink in one swipe,” Crawford says. “If you are removing the marker at the cutting edge, your edge angle is too high and you are micro-beveling.” From there adjust your edge angle to a lower degree and take a few more passes to see how the ink is being removed. “It is a process of trial and error,” Crawford notes.
Tobler is another proponent of the marker method. “It helps for matching the edge angle already on the blade when resharpening,” she observes. You can use the method in conjunction with one of the guide kits even if the kit holds the angle constant for you. The method enables you to see how much more you must sharpen off in order for the edge bevel to be reestablished. In this regard, you’re using it to determine how much more you have to go as opposed to if you’re holding the angle correctly.
Another tip is to sharpen in a well-lighted area. Good visibility is very important and key to doing a thorough, well-executed sharpening job. And if you use the marker method a lot, abundant lighting helps you see clearer without eye strain.
Finally is sharpener selection. You can use any quality sharpener as long as it fits the steel type. The key here is to select a sharpener you feel very comfortable in using.
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