A Beginner's Guide to Knife Sharpening
Posted by Kristie French on
This is intended to help you get started sharpening knives on a 1X30 belt sander, such as the popular Harbor Freight 1X30 Belt Sander. Most of the information below can also be applied to other belt sanding machines.
Setting Up Your Machine:
Before you begin sharpening it’s important that you equip yourself with appropriate ANSI safety goggles, tie back long hair, and make sure any dangling jewelry or loose clothing will not come into contact with the machine. It’s also important to familiarize yourself with your 1X30 inch sander’s instructions to ensure you are using it correctly and safely. Always keep the top and side safety guards on when operating your machine. You will also want to make sure your machine is on a sturdy surface. Bolting the feet in place to prevent movement is advised. When you fit your first abrasive belt, you may find that you need to adjust the belt tracking/tensioner located toward the back of your machine. If the tensioner seems tight or immobile, it may need to be loosened. In some cases the tensioner may need to be removed so the paint underneath can be sanded down to increase mobility. We recommend not attaching the table feature that comes with the sander, it can get in the way while sharpening. We also advise removing the platen or moving it back to where it is not touching the abrasive belt.
Analyzing Your Knife & Picking Your Abrasive Belt:
Here is a representation of a basic kitchen style knife with different parts identified:
After you are confident with the setup of your machine and have adhered to all safety protocols, it’s time to take a look at your knife. Analyzing your knife metal quality, the thickness, if it has a broken tip, if it’s chipped, has a heavily worn edge, or needs to be reshaped are all factors in what abrasive belt to begin with. Most knives are made from a type of steel. Most commonly carbon steel, stainless steel, tool steel, or alloy steel. You will notice that some of the lesser quality steels are softer and wear away faster. If your knife is a softer metal or is thin and has no major damages or reshaping required you can start with a high abrasive belt such as an 600 or 800 grit. That being said, if your knife will require a substantial amount of metal to be removed (for large chips, missing tips, or for dramatic reshaping) you may want to lower the abrasive you start with to a 320 or 400 grit. Reference the chart below for starting abrasive advice.
Choosing Your Sharpening Angle:
The next step is to decide what angle to sharpen with. Before we explain finding your angle, it’s important to know that the sharpening technique we will be explaining is called Edge Trailing, meaning the edge of the blade is pointed in the direction the belt is moving. You can read up on the differences between Edge Trailing and Edge Leading here. Now, there are a few ways to find your knife’s angle. If you want to maintain the angle already established on your knife you can find and follow that angle using a sharpie scratch test. How you do this is simple. Along the bevel of your knife use an indelible marker to make about an inch long mark. Then with the machine turned off, line up the bevel edge as though you are about to sharpen it. Try to remain consistent with your motions and rub the edge back and forth a few times to remove the marker. Examine the edge, if the marker is evenly removed along the edge without going over, you have your angle! If you want to correct an angle but don’t know what the best angle for your knife is refer to the chart below for common angles. Or you can read more about finding angles here.
Having a hard time envisioning an angle without the use of a protractor or a special knife angle calculator? You can estimate an angle by holding the blade perpendicular to the belt. Then tilt the blade to split the distance between the blade and the belt. This is a 45 degree angle, split the difference once more and you have a 22.5 degree angle. 22 is a very common and functional angle for a number of applications and blade types. Alternatively, we do offer an angle guide that will help you set and keep a constant angle. Keep in mind this guide is for sharpening edge leading. If you would like to use the angle guide, start on a low grit since sharpening this way will remove metal more quickly than sharpening edge trailing. It’s also important to know that even when you are sharpening edge leading, you need to strop edge trailing at the end. When using the angle guide, you also need to remove the guide before stropping.
Now that you know what abrasive you want to start with and the angle you wish to achieve, it’s time to start the sharpening process. Let’s talk more about that. The idea of sharpening is to remove enough metal to create a new edge with an ideal shape free from chips, knicks, or dents. When you do this you will be creating a burr on the edge. This burr will then need to be weakened and removed throughout the sharpening process. This will occur when you do a grit progression and finish with a strop. Begin with your first and lowest grit abrasive belt on your sander. Remember we will be explaining how to sharpen edge trailing, so make sure the edge of your blade is pointed in the direction your belt is running. Begin by bringing the heel of your knife to the running abrasive belt. If there is an unsharpened section near the handle (the bolster) begin just before that point so as not to remove metal from it. It’s important that when the blade makes contact you immediately continue down the length of the blade. It’s tempting to hold it there for a few seconds, but to avoid removing more metal at this section than the rest of the blade, a consistent motion is important. When you reach the tip of the blade make sure you remove the blade before the tip completely clears the edge of the abrasive belt. When the tip is about halfway across the belt, simply pull the knife back toward you. After a couple passes on one side of the knife it’s time to check for a burr. The burr will be on the opposite side that was not in contact with the abrasive belt. You may or may not have seen a small burr appear along the edge. It will look like a thin white line when reflecting light. You can feel for the burr with your finger by gently passing your finger down the knife to the edge (not into the edge, we have to stay safe). You’ll be able to feel a slight ridge catch your finger. Feel in this same motion down the entire edge to make sure you created the burr evenly all the way across. You may need to do a few more passes. If you aren’t noticing a burr you may need to drop down to a lower abrasive or adjust your angle. When you have a good even burr, flip the knife to the other side and repeat using the same technique. This time you will want to feel both sides to see 1) that the burr has been completely removed from the side against the abrasive belt and 2) that the burr is even on the opposite side. You will want to make sure any imperfections are corrected at this Such as removing enough metal to get past knicks or chips. You will also need to correct the shape of your edge if it needs it (this is a bit more advanced, you may want to start with a simpler knife that hasn’t been misshapen.) When you have your new edge created it’s time to move to a higher abrasive belt. This is purely for the purpose of weakening the burr you created. You generally will only need to do a few passes on each side. If you started with a low abrasive, such as an 80 or 120 grit, you can jump to around 220 or 400. If you started with around a 400 to 600, you can jump to around 600 or 1000 grit. See the grit progression chart below.
As with most steps in the process, you will learn from experience what abrasives you tend to gravitate towards. After this grit, you may or may not need a third abrasive belt. It will depend on how weakened the burr is. For instance if you went from an 80 grit to a 220 grit you may want to follow up with a 600 then 1000 grit before continuing on. Once you have diminished the burr by following an abrasive belt progression, it’s time to bust out the premium leather Super Strop. This is the final step in sharpening and is how you completely remove your burr. There are some cases in which you may want to retain a slight burr, such as for Chefs who have a designated tomato cutting knife. However, for most practical applications an improperly removed burr (also called a wire edge), will fold over the edge dulling and damaging the edge of your knife. So let’s remove that burr! Load your strop onto your machine. With the machine running apply honing compound. All of our premium leather Super Strops come with either white or green honing compound (2 packs come with both!). The majority of your sharpening jobs will need the white honing compound. It’s more abrasive and is perfect for removing a burr. The green compound is less abrasive and is more ideally suited for honing in between sharpening. To open the compound, use a pair of pliers to remove the metal bottom then use your thumb to move the compound up through the tube. The compound is solid and the motion of the moving strop will melt the compound onto the belt. You only need to run the compound back and forth across the strop for about 3 seconds. It may be hard to see initially, but when you strop the blade you will notice black or grey streaks appear. There’s no need to put the compound on thick, the goal is to slowly build an even layer of compound over time. You will hone the same as you sharpened (unless you sharpened Edge Leading with the edge pointed into the motion of the belt). Honing must always be done Edge Trailing. Using the same angle or slightly lower angle than you used with the abrasive belts, follow the same motion across the stropping belt. Heel to tip, making sure not to drag to point completely across the belt. This can cut the belt. After only one or two passes you may see the burr be removed from the edge. Feel for it and if it’s gone, flip to the other side, apply a little more compound, and complete a few more passes. It’s important to not do too many passes, because you could start to round the edge. Pro tip, always remove your belts when not in use to help avoid stretching. Check for the burr again, and if it’s gone you did it! Your knife is sharpened. A great way to test out the new edge is on a standard sheet of 20 lbs paper. If the burr is removed, your knife should slice through the paper with ease.
Remember, sharpening takes practice. A great way to start out is on inexpensive knives, you could even pick up a few from a thrift store to start with. And if you are ever stumped, reach out. We are happy to help.
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