We all use knives around the kitchen. In addition, many of us carry a pocketknife regularly. What is often misunderstood is how to sharpen a knife properly to ensure a good cutting edge that won’t dull quickly with use. There are 5 reasons your knife won’t take a sharp edge or won’t hold a sharp edge.
Understanding how the edge of a sharp knife works is key to properly creating a blade edge for long-lasting sharpness. A sharp knife edge can be accomplished in several ways with several different tools. However, if the tools are not used properly, you may never get a sharp edge on your knife.
Technique is the Most Important Aspect of Knife Sharpening
In most instances, if you can’t get a sharp edge on your knife, the cause is related to improper sharpening techniques. Sharpening at the wrong angle can leave your knife dull or with an edge that won’t stand up to use. Inconsistency as you hone the blade can also cause problems. The steel of your knife may make it almost impossible to get a sharp edge.
More than likely, if you can’t get a sharp edge on your knife, the problem is related to your sharpening technique. There are three technical aspects of sharpening a knife that goes hand in hand with achieving a sharp edge. Two other mechanical issues can also make it impossible to put an edge on a blade.
It is easy to get a sharp edge on most knives if you follow some simple steps and practice to hone your technique. Sharpening a knife properly is all about angles—understanding how the angle of your knife works is a key element in getting a sharp edge.
You Must Sharpen at the Correct Angle
The correct sharpening angle for your knife is determined by the angle of the grind on the knife. . The original angle of the edge grind varies from knife to knife. The type of edge on your knife can also determine the angle you should use when sharpening.
Many people use tools or guides to sharpen their knives. These guides often have preset angles. These tools are great if the grind angle of your blade matches one of the preset angles on your tool. However, using a guide with angle presets can keep you from putting a sharp edge on your knife.
Sharpening at Too Low an Angle
Your knife blade is a complex set of angles that must work together for a sharp edge. If these angles don’t meet properly, you will never have a sharp knife that will hold an edge. A sharpening angle that is too low can keep your sharpening stone from addressing the right portion of the blade.
A low angle of attack on your sharpening stone raises the blade's cutting edge above the stone. The stone begins to remove metal from the angle where the bevel meets the flat of the blade. With time and effort, you can remove enough metal from the blade to lengthen the bevel to the shallower angle and create a sharp edge.
However, this will often result in a knife that may take a very sharp edge but won’t hold the edge during use because of the thinness of the metal at the cutting edge. You can remove enough metal to weaken the knife enough to cause flexing problems along the edge.
Sharpening at Too High an Angle
Keeping too high an angle on your knife as you sharpen risks creating a double bevel on the cutting edge. A double bevel on your knife is never a good idea. It is almost impossible to attain a sharp, cutting edge if you create a double bevel on the edge of your knife.
A high sharpening angle is, in effect, dulling your knife’s blade with each pass on your sharpening stone. The higher the angle difference, the more problems you can inflict on your knife blade. A double bevel cut deeply makes it difficult to resharpen your knife to the proper angles without serious grinding and sharpening work.
What is the Correct Angle for Sharpening a Knife?
The easiest way to judge the proper angle to sharpen your knife is to look at how the bevel meets your sharpening stone. In general, the bevel of your knife should rest flat on the surface of your sharpening stone. As you move the knife over the stone, the bevel should remain flat without lifting the edge or raising the blade's flat.
As you work the edge of your knife over your sharpening stone, check the marks on the bevel of the blade frequently. The sharpening marks should be consistent over the whole edge bevel to ensure that you are at the right angle of attack on the sharpening stone.
Failure to Maintain a Consistent Angle of Attack
When using a sharpening stone, consistency is a major problem preventing a sharp edge on your knife. The edge of your knife is a precise line where the two bevels meet. If your angle of attack is inconsistent as you sharpen, you will never achieve a fine line that means a sharp blade.
As you move your blade across the sharpening stone, it is easy for the blade to change angles in a rocking motion. Even the slightest change in angles while sharpening leads to a wavy line at the edge of the blade. A wavy line will never create a sharp edge.
Maintaining a consistent angle of attack when sharpening freehand takes skill and practice. Many knife owners resort to sharpening jigs or tools that help maintain a consistent angle of attack. Unfortunately, many of the jigs don’t allow you to fine-tune the angle of attack. You must sharpen using a preset angle that often doesn’t match the bevel grind of your knife.
There are sharpening guides on the market that allow the angle of attack to be fine-tuned to match the bevel grind of your knife. Most of these tools can be used with standard sharpening stones. Some come with sets of sharpening stones that work with the guide to give precise angles and offer a variety of stone coarseness.
Failure to Sharpen to the Edge of your Knife Blade
Many knife owners fail to achieve a sharp edge because they stop sharpening their blades too early. Failing to start with a coarse enough stone to remove any damage or unevenness is another problem. Sharpening until you have created a burr on the edge is the key to a sharp knife.
As you sharpen your knife, you are removing metal from the blade. There are several aspects of this process that need to be on your mind.
- You must remove metal equally from both sides of the knife blade. Use your sharpening stone for the same number of strokes on each side of the blade. This ensures that you are removing metal at the same rate on both sides of the bevel.
- Use the right coarseness of stone depending on how much metal you need to remove. If your blade has been poorly sharpened or is damaged from heavy use, start with a coarse stone, and then use finer stones to get the final edge.
- Watch for the burr on the edge of the blade. A burr will form on the edge when the blade is at its sharpest. Learn to feel for the burr on your knife edge and how to remove the burr properly. You can remove the burr with your sharpening stone. However, many people prefer to use a leather strop or other methods to remove the burr easily.
If you don’t create a burr on the cutting edge of your knife blade, you are not sharpening to the edge of the blade, or your angles are inconsistent. A burr is the best indication that you have sharpened to the blade's edge and have created a consistent edge line along the blade.
Damaged Knives Can Make It Impossible to Get a Sharp Edge
Like any tool, knives are expected to suffer wear and tear. Normal use should not create damage that prevents achieving a sharp edge. Knives can be dropped or bent, preventing them from being sharpened properly. If you have trouble getting a sharp edge, inspect your knife carefully for damage.
Any knife that is clearly damaged should not be used. A professional knifemaker may restore expensive knives. A bent knife is dangerous to use and may fail catastrophically. Straightening a bent knife takes skill and the proper equipment. In most cases, the best course of action is to dispose of the knife.
The cutting edge of a knife may suffer from being dropped against hard objects. The edge may chip or ding significantly, rendering the knife unusable. It may be impossible to sharpen a dinged or chipped edge. In most cases, the blade of the damaged knife must be reground to remove this kind of damage. A knifemaker can often perform this type of repair.
Knife blades may also crack. Often this is a problem with knives made of inferior steel, but it can happen on the most expensive knives. Metal can suffer from fatigue or irregularities in the structure. A cracked knife blade should be taken out of use immediately.
Poor Quality Steel May Not Take or Hold and Edge
A knife blade depends on the quality of the steel in the blade to take and keep a sharp edge. Steel that is too soft won’t sharpen easily and will dull quickly. Steel that is too brittle can be almost impossible to sharpen to an edge and sometimes break or chip when used.
All in all, the best gauge of the steel in your knife is the reputation of the knifemaker. Most reputable knifemakers not only stamp their names on the blade, but they also put the steel alloy number on as well. It may take a bit of due diligence as thousands of steel alloys are used to make knives.
Any knives coming from overseas often use inferior or low-quality steel for the blades. Often these blades use mild steel or are brittle due to the manufacturing processes used. It is hard to tell from a visual examination the quality of steel used to make a knife.
Unfortunately, knives with a high level of craftsmanship and quality steel are pricey at best. Finding the right blend of price, quality, and craftsmanship is the challenge for anyone shopping for a long-lasting knife.
Using the Right Tools is a Must
The right tools will make putting and keeping a sharp edge on your knife much easier and safer. In general, you will need a set of whetstones, lubricant, a blade guide, and a soft cloth to clean your knife as you sharpen. Some people prefer a sharpening kit or machine.
The basic tool for sharpening knives is a set of good whetstones. You need at least three grits of stone to care for your knives properly. Your whetstone kit should include a holder to keep the whetstone flat and secure as your work. In addition, the whetstone should be large enough to accommodate your biggest blade easily.
Some stones require oil, while others can be used with water. It is a matter of personal preference in our opinion. Either one will work if used with the proper whetstone. The lubricants help carry the metal shavings and stone particles away from the sharpening surface.
Sharpening machines can be very efficient. They can also destroy a good knife blade in seconds if not used correctly. A good whetstone keeps you under control and focused on the knife. Machines tend to work fast, removing a lot of metal with each pass.
A good blade guide can be a wise investment, especially if you have trouble maintaining a constant angle of attach when you are sharpening. You should find a blade guide that lets you adjust the angle of attack so that the bevel edge of your knife lays flat on the whetstone. Avoid sharpening kits that force you to use a preset angle that may not match the grind of your knife.
Putting an Edge on your Knife
Learning to sharpen your knife to that razor edge is both art and science. Understanding bevels, grinds, and angles can teach how your sharpening tools should be used. Learning to apply those tools and what to look for as you sharpen your knife is more art than science. Using the tools improperly or inconsistently will leave you frustrated and with a knife that never gets sharp.