Why is my knife not getting sharp?
Why Is My Knife Not Getting Sharp?
I’ve been sharpening for hours but my knife still isn’t getting sharp. What can I be doing wrong?
We often get this call or email from customers. It can be very frustrating and may even force you to give up sharpening. But as frustrating as spending time sharpening a knife can be without getting it sharp, we have found that most problems can be easily solved.
When we work with the customer to troubleshoot what is going on, we focus on three main factors:
Sharpening at the Correct Angle - An important note: by "correct" we mean matching the angle currently on the knife regardless of actual degree of that angle. Matching the existing angle will give you the best chance to get results. Sharpening at a higher angle will tend to give you a less sharp edge, sharpening at a lower angle will greatly increase the time it takes to sharpen the knife.
Maintaining a Consistent Angle - This is a fancy way of saying don't rock the edge when you sharpen. Once you have established that you are at the correct angle, you need to stay at that angle. A rocking motion creates a dull rounded edge.
Sharpening All the Way to the Edge - We could also call this, "Did You Start with a Coarse Enough Grit?" In order to create a sharp edge, both sides of the edges being sharpened must meet at a line. Removing material until that intersection is achieved is the only way to accomplish this. We find that in problem cases people often simply haven't created an edge with their first grit.
We've illustrated each of these main factors below.
Sharpen to the Correct Angle
Check that your sharpening angle matches the existing angle on the knife. To do this, use a marker to color the bevel of your knife. Then do 3 or 4 strokes on a stone. Look at the bevel to see where you have removed the marker. You should be able to quickly see if you are matching the angle or not. If you've removed the marked area above the edge, you're too low. If you've removed marked area only at the very edge, you're probably too high. If you've removed the marked area in the middle of the bevel, you're about right.
The question of what specific degree you should sharpen your knife to is a topic we cover elsewhere. For a deeper look at angles in specific degrees, see our article Detailed Discussion of Knife Angles.
You may find that you are at the correct angle. Or you may find that you are too low or too high. Each of these conditions has implications.
Sharpening Angle Too Low
When you sharpen at an angle lower than the existing angle, all of the material you remove is away from the cutting edge. You will have to continue working until you have recreated the bevel all the way to the cutting edge. This will increase the amount of time that it will take to sharpen. You can adjust your angle or continue at the lower angle, knowing that it will just take longer to sharpen.
Sharpening Angle Too High
Sharpening at too high of an angle concentrates all of your effort right at the cutting edge. It is possible to create a cutting angle that is impractically steep and feels dull. Essentially, if you are working at too high of an angle, you may be blunting your edge. In practice, an angle that is only slightly too steep will not dull the edge. Only very high angles will create edges that feel dull. Sharpening at a slightly higher angle will actually speed up sharpening, but at the expense of maximum sharpness.
Sharpening Angle Correct
If the sharpening angle matches the existing angle on the knife, you are in a good position to recreate the edge that was once sharp.
Maintain a Consistent Angle
Using the marker test, you may find that you are sharpening with a rocking motion, alternating between too low of an angle and too high of one.
Rocking Motion
Rocking rounds the edge. A rounded edge is a dull edge.
Keys to keeping your angle constant are to slow down and to simplify your motion. As with many things, rushing does not actually make things go faster. A slow, steady stroke is more efficient than a fast jerky one. In the same vein, a simpler motion is usually steadier than a complicated one. Find a technique that you can successfully repeat. Another option is to use an angle guide like the DMT Knife Sharpening Guide.
Sharpen All the Way to the Edge
The goal is to sharpen until you have created an edge. A burr is an indicator of whether or not you have achieved this. The presence of a burr indicates that you have created an edge. If you don't have a burr, you haven't sharpened all the way to the edge yet and will need to continue, preferably with a coarser grit stone, until you do have a burr.
The first grit used in any sharpening session provides the foundation for all the work that follows. If the metal hasn't been removed all the way to the edge with the first grit, any following grits stand little or no chance of creating a sharper edge. Remember that a 5000 grit stone will take exponentially longer than a 1000 grit to remove the same amount of material. And a 1000 grit will take exponentially longer than a 220 grit. So if you are spending time without getting an edge, you should try a coarser grit.
Unfamiliar with burrs and how to go about detecting them? See our article Feeling for a Burr for more information.
No Burr Yet
No burr indicates that the bevels do not meet in at the edge. They are coming together on the curve before the edge, and not meeting at the edge. You must continue to sharpen until both sides meet at the edge. A coarser grit is most often what is called for in this situation. If you have been sharpening for more then a couple of dozen strokes, and don't feel a burr indicating that you have sharpened all the way to the edge, switch to a coarser grit stone and try again. This one point alone can save more time than anything else you do.
Burr Present
The presence of a burr indicates that the bevels are coming together as an edge. Once you have created a burr, you are ready to repeat the process on the other side of the knife and then to proceed through your remaining grits.
Final Thoughts
These are the most common reasons why a knife isn't getting sharp. If you're having trouble, it pays to take a step back and evaluate the most common mistakes that we've discussed above. It is best to evaluate the steps in order to help diagnose your situation.
If you have followed these steps and are still having difficulty getting a sharp edge, get in touch with us. We'll be happy to help.