Sharpening a knife can be a therapeutic and relaxing experience, but it’s also an absolute necessity. Using a dull knife in the field can lead to all sorts of harmful situations, which I outlined in a previous knife safety article. In this entry I would like to discuss some basic knife sharpening and repair methods, with the understanding that my way is A way, not THE way.
Knife sharpening is a learned skill that must be honed just like your knives.
There are several ways to sharpen a knife. Stones, rods, stropping, carbide, manually, mechanically, pull sharpeners, and many others. With as many methods of sharpening your blade, there are even more ways to do it wrong. Learning some basic angles and their intended use is imperative to getting the right edge on your knife. With the knowledge you will receive in this article, you will be well on your way to getting that razor sharp edge you want.
There are 3 basic edge profiles that you are likely to want to consider. While there are thousands of folks out there that have some personal preference that they believe is the only edge profile you will ever need, you must take any information you receive on the matter with a grain of salt. In my experience, the 3 edge profiles are as follows:
12-15 degrees- This angle is typical of edges on razors and other blades like X-Acto or fillet knives. While the edge is very sharp, it will not be very strong no matter the metallurgy of the blade. This angle is typical of knives that are not subject to very heavy use so having the weaker edge is not a deal breaker. I would recommend against this for field knives.
22.5-30 degrees- Typical for field knives and things of the like. This particular angle provides a very sharp blade, without the thinness and bend-ability of edges at lower angles. I use a 22.5-25 degree angle on my field knives for more than one reason. One being the durability of the edge, and another being the ease of sharpening due to the easily found sweet spot for the angle, which I will go over shortly.
35-40 degrees- Usually seen on machetes, axes, and heavier blades, this angle is also easy to find when working on your edge. With a very broad profile and a very strong edge, the 40 degree angle is best served for chopping, and not carving. The angle grants the edge more of a chisel-type profile that splits wide and is not well served for finer cutting tasks.
With these three profiles in mind you can determine the best angle to use for your knives based on their intended use. Regardless of your chosen bevel angle, be sure to maintain the angle for the full draw across the stone. The draw should be in a steady, sweeping arc from heel to tip. I use 10 draw strokes for each side on each grit. Finding the right angles when sharpening your blade is easier than you might think. Below are a few methods I have used over the years:
Quarters- Using quarters is a pretty easy way to get an idea of the angle in which you will want to hold your blade when drawing the knife across the stone. The idea being that you stack a certain number of quarters depending on the height of your blade and the angle in which you wish to bevel the edge. Stacking the quarters on the stone and resting the spine on the edge of the top quarter will give you a pretty good idea of how the angle should feel and look like when you are drawing the knife across the stone. There are varying opinions on the math behind the use of quarters, but I did a little bit of testing and came up with 8 quarters for the 1.5” tall blade on my primary field knife when sharpening to 22.5 degrees. The Leatherman pocket tool I carry has a ½” tall blade which necessitates 3 quarters for the same angle. Experiment a bit with your knives to determine the right stack height for your blade. Once you get a good feel for the bevel angle, you can get to work.
Wood wedge- While not everyone has a spare miter saw in the garage, making your own blade guide can be pretty easy. Find a square piece of scrap wood around 2”x 2”. Using a good 90 degree corner of the piece, draw a diagonal line from one corner to the other. That will be (roughly) 45 degrees. Draw another line from the bottom tip to the vertical halfway point off the base and that should be around 22.5 degrees. Cut along the second line and voila! You’ve got your very own blade guide. Place your handy dandy new tool on the stone and rest your blade on it, with the edge of the blade on the stone itself. You can use the block while drawing the blade across the stone, but I would recommend just using it as a reference guide. You can add or remove more angle on the wood to create guides for the desired angles for all of your tools.
Folded paper- You can easily make your own paper guide by folding a square piece of paper diagonally, thus creating a 45 degree angle. Fold the paper again to create a 22.5 degree angle. Use the paper as a reference guide for your bevel angle.
Now that you know how to find the right angle, let’s discuss stone selection. If you choose to use a stone as your primary sharpening method, you may feel a bit overwhelmed when you start shopping for them. A good education can usually be found at your local knife shop, but I will try to break it down for you here:
Arkansas stones- My preferred stones, these are a natural stone that is processed from bigger Novaculite rocks in Arkansas. With varying grits, these stones can be used to restore a very dull blade into a razor sharp tool. While these stones will give you years of service, they do wear and require flattening from time to time. It is strongly recommended to use oil with these stones, but I have used water with them for many years with no negative effects. Maybe I will have to use oil for a while to see how it works out, but only if I can use my trusty veggie oil!
Diamond stones- Using very small (<60 microns) industrial diamonds on a flat surface, you get a very quick and easy edge using diamond stones. They use water for removing material from the sharpening surface, making cleanup much easier and faster. While the initial cost of diamond stones can be high, you will get many years out of your stone and no wear on the profile, which means no need to re-flatten as with other stones.
India stones- Made of Aluminum Oxide, these stones are typically the least expensive but do have the drawback of not being able to hone to a very fine edge. They will be fine for field work and you may never need a sharper edge than they can provide so they may be perfect for you. These also require oil to remove material. I recently ordered a set of India stones and will report back with my results after some use.
Water stones- Made of the same Aluminum Oxide as the India stones, the material is held together with a different bonding agent that allows you to quickly and easily hone your edge, but at the cost of durability. The compound in the stone wears much faster than India stones and requires flattening more often. While you can hone a very fine edge, you will not get that polished look you can get with a hard Arkansas stone.
With that education on stones out of the way we can talk about alternative methods like pull sharpeners, pocket sharpeners, and rods. Each having their own pros and cons, you will see why each may have a place in your tool bag:
*NOTE: As this article is intended to discuss sharpening in the field, I will not address electric sharpeners and clamp kits.
Pull sharpeners- Pull sharpeners have gained popularity over the last decade or so due to their inherent ease of use and speed. Typically found in a kitchen, pull sharpeners use carbide edges to cut off blade material which has a tendency to wear a knife faster than stones, but is safer to use.
Pocket sharpeners- For my pocket sharpener, I use a Smith’s Pocket Pal. The Pocket Pal has both carbide and ceramic sharpeners and works very well. With the addition of a serrated blade sharpener, the Pocket Pal will also sharpen gut hooks and can be used for minor edge repairs. Many pocket sharpeners rely solely on carbide to remove material like a pull sharpener, but I recommend something a bit more feature packed to increase its usefulness and reduce the number of individual tools and weight you will need to carry. There are a lot of options for pocket sharpeners out there, so choose wisely, and put it to the test before you head out.
Rods- I have used sharpening rods for many years, and find them to work fine, so long as you replace the rods regularly. I tend to sharpen a lot, and rods have less material than stones and require replacement more often than I prefer. With varying materials and grits, rods can be a handy tool that takes up little space, and usually store in their own base. Their bases typically have holes pre-drilled into the wood or plastic at an angle that allows you to sharpen with a downward stroke while keeping the blade itself at a 90 degree angle.
Once you are finished, you can use a few methods to test the edge. I typically use paper when I am in the garage. Hold the paper vertically at the top of the page and place the heel of the blade onto the paper and pull back in a drawing motion without pushing down and allowing the weight of the knife to move the blade through the paper. If the blade pushes or tears the paper, you are not done. If the blade cuts a clean line through the entire stroke, crack open a cold one and bask in your greatness. Another method is to try to shave the hair off of your arm. A dull blade will push the hair down instead of cut through it. Only the finest edges will cut all the hairs in one pass, but if the blade cuts though a good amount of the hair in one pass, you are probably fine for field work. These methods allow you to test the entire blade edge instead of a small portion like the thumb drag or fingernail tests do.
Let’s talk about edge repairs for a moment. Most basic edge damage can easily be fixed by simply sharpening your knife, starting with a very coarse stone to reshape your blade. Draw the blade as if you were simply trying to sharpen the edge, and the damage should be remedied. If the edge damage is too great to realistically repair using this method, then it may very well be time to replace the knife. I know that sounds like a terrible solution, but no matter what method you use, you will need to remove material until the blade edge is flat again. Once you have achieved this, move up in the grit to your desired sharpness. It is up to you to determine how much material you are willing to sacrifice before the blade is simply too far gone. In the field, replacement is not an option and you will need to continue with the coarse stone until the edge is flat. An uneven edge can be dangerous to use, so grind away. This may necessitate the removal of an obnoxious amount of steel from your knife, but if it is all you’ve got then you do what you have to do.
Be sure to keep a rag handy to wipe material away from the stone and blade. I use the same rag to clean that I use to apply the veggie oil to my blade. It comes in handy for storing my stones as well. Some prefer using wooden or plastic boxes, but I see these as unnecessary bulk. When I need a base for the stones, I simply find a branch about 3” wide and split it in half, creating a flat bottom. I cut the branch to about 2” longer than my stones, and baton out a flat chunk of the branch to place my stone inside, giving me a base that I did not have to carry with me. You can use wet or dry wood for this task.
Knife sharpening is a learned skill that must be honed just like your knives. With practice and experimentation, you will learn to sharpen just about any blade in any angle needed. I have been doing it for almost 30 years and I am still learning new ways to make sharpening my knives easier and safer. Having a sharp knife will make your life in the field easier and safer. Don’t Die Dumb.