Things to know about axes

Q: Why is the axe the coolest tool in the world?

A: In the beginning, before early man, we did not make tools for future use. The first tool was probably a broken stone that someone picked up on a beach. Accidentally breaking the stone and later on intentionally chipping it got us a better cutting edge. We started making these very basic hand axes around 2,5 million years ago.

Many authorities agree that the making of the axe is the one event that separated the sub-man from true-man in early human history. The important factor was not the axe itself, but the thought process that went into the making of our own tools for future use.

The most important factor in our human evolution has been technology, and the most important technology has been the development of tools. Among these, the most important tool has been the axe.

It is probably quite few that is really aware of the importance of the axe. Axes and knifes, often being the only tools at hand, allowed us to turn forest into farm lands, build houses and shelter, harvest and split firewood, make other tools to hunt, gather and process foods, build furniture and household items and fix broken things. We literally could not live without them.

Q: How do I care for my axe?

A: When carving, care for the edge by not carving in dirty wood. Soil or dirt on the bark or in the chopping block can damage the edge. Do not lean your foot on the chopping block, as dirt from your shoe can get into it. We recommend to keep the wood and chopping block clean with a hard brush.

A good axe should always be kept sharp. It is easier to maintain the edge by honing it after each use compared to waiting until the edge is all worn and then needing to do a full resharpening.

After using the axe, clean it by wiping off moist and small wood chips with some cloth. Oil it to protect from rust. We recommend vegetable oils like jojoba oil or similar. For storage and transportation, always use the axe cover to protect the edge.

When not in use, store the axe in normal room temperature and in normal humidity. Storing the axe next to a radiator or stove might risk the handle to shrink and come loose. A damp basement might risk the head to rust and the handle to mould.

Q: How do alloy elements effect the steel?

A: Steel consist of iron mixed with small quantities of alloy elements. The elements are added to change the properties of the steel. The elements can make the steel harder, tougher, rust proof or other properties. Metallurgists look for the right mix for the intended use of the steel, similar to how a chef use spices to flavor different dishes.

For tool steel the most important element is carbon because the it allows the steel to be hardened. The more carbon the higher possible hardness. The carbon improves the wear resistance, but it can also make it more brittle. For carbon levels, the more the better is not true. Use the right amount of carbon to get desired hardness, but not more than that, to avoid brittleness.

Other common elements are Vanadium, Manganese, Chrome and Silicon. The molybdenum increases ability to harden, increases wear resistance and reduces brittleness. The vanadium helps to get a finer grain during forging. Silicon improves toughness.

Q: How does heat treatment work?

A: Heat treatment is a process in which metal is heated and cooled under tight controls to change the steels characteristics. It can soften metal to improve formability. It can make things harder to improve strength. It can put a hard surface on something soft to increase abrasion resistance. And, it can toughen brittle products. Different types of heat treatment is normalizing, hardening, tempering and annealing.

Each heat treating process requires three steps: first heating to a specified temperature, then holding at that temperature for the appropriate amount of time, and the last is cooling. Most common is cooling by quenching in oil or water. Each steel has recommendations on temperatures, holding times and cooling methods depending on its mix of alloys.

The attention to detail in each step and for each type of heat treatment makes a big difference for accuracy. First thing is to respect the holding times to make sure each transformation gets solid. Another thing is to measure and adjust that the oven temperature is the same in all areas to assure all get the same treatment. The carbon content in the hot air can be harmonized with the steel to minimize decarbonizing. The dipping into the quench and how the liquid flows around the piece will effect the solidity of the hardening. These details are examples that make a difference in how well the heat treatment turns out.

Q: What makes the edge hold longer?

A: How long the edge stay sharp depend on several things. The steel quality and alloy, the heat treatment, how narrow the edge is, your handling of the axe and what material you work in.

A good quality steel with proper alloys for an axe makes the edge last longer. The edge must be able to take and hold and edge for a long time, and at the same time the steel should allow for the axe head to take a lot of abuse. To satisfy these different demands, the steel needs alloys that makes the perfect balance of hardness and toughness.

Taking no shortcuts in heat treatment makes the edge last longer. An important factor is keeping right hold times on each temperature. The heat treatment should make the edge harder and the axe head tougher, so different zones of the axe needs different treatment. The edge is more sensitive than the head, so getting the edge exactly the treatment it needs is priority. After that, the eye zone is brought down to desired toughness in a quicker way. This is better than the other way around. 

A fatter bevel makes the edge last longer. It can take more abuse and still maintain sharpness. This is why we recommend not regrinding down the bevel to a narrower angle. The more polished it is the longer it lasts, since sharpening marks can indicate a damage.

Lastly, your way of handling the axe and what wood you work in matters. Keep that in mind that harder wood and dry knots in some wood can be tough on the edge. In addition, keep the chopping block and work piece clean from dirt, and always keep the leather cover on when not in use.

Q: What sharpening equipment should I use?

A: There is a variety of sharpening equipment out there. Powered equipment is faster, but if not cooled, it comes with a big risk to overheat the edge. At 200 degrees Celsius the edge looses hardness and gets soft. This is why we recommend water cooled grinding wheels, bench stones or hand held stones.

Hand held stones or bench stones are good because they do not overheat the edge, they require no power and can be quite cheap. Water cooled grinding wheels are also good but can be a bigger investment. Both options are used with water, which keeps the stone clean and sharp, washes off sharpening dust, and protects the edge from getting hot. For a beginner, it is cheaper to get a sharpening set with a few whetstones in different grits than getting a water cooled grinding wheel.

For honing, we recommend a wooden strop with polish paste, diamond sharpening steel or a very fine whetstone.

Q: What about bevel geometry?

A: For a quick touch up to get the axe sharp, a slight concave bevel is good. If sharpening horisontal on a grinding wheel, the bevel gets concave from the stone radius. A too deep concave bevel from a small radius stone makes the edge too thin, which is less durable and sucks into the wood.

The whetstone is flat and will make a flat bevel, and you can also grind a flat bevel on a grinding wheel if you grind diagonal or vertical. A flat bevel will last longer because there is more material near the very tip of the edge, making it slightly tougher. A flat bevel picks up the fibers in the strike without sucking in or bouncing off the wood.

A strongly convex bevel is not desirable for carving axes because it makes the axe bounce off the wood. If the bevel is strongly convex you need to chop in a bigger angle for the bevel to pick up the fibers, making it unsteady. But, a slight convex can be good if you want to make a finish pattern with round marks from the axe bouncing off the wood. Some people like it slightly convex so that the strike “carves outwards”.

A mini bevel from honing is ok to have no matter if you have a concave, flat och convex bevel. If the mini bevel gets too big, making it more of a secondary bevel, if does not work well for carving, so avoid that.

Q: How do I sharpen my axe?

A: A good axe should always be sharp. Sharpening is done in three steps: grinding, sharpening and honing. If the edge is damaged or is very dull, start with grinding. If it's just normally worn, sharpening and honing is enough. To quickly touch up the edge, just hone it.

When grinding you want to remove edge wounds, keep the edge line as it was, and get the right angle. We recommend to not grind the bevel narrower than 30 degrees for best edge retention. A good trick is to use a felt pen to mark where to remove material. Another trick is to use an angle guide to get the right angle. Alternate from side to side for an even result.

Next is sharpening. Sharpen with finer grit in one or several steps. Alternate from side to side until a burr appears. Burr is steel fragments hanging from the edge after reaching its very tip. The sharpening is done when the coarse sharpening marks are gone. You have sharpened all the way to the tip when you feel the burr along one side and when alternating, you feel it along the other side.

Hone off the burr to get the axe sharp. Work in the same angle as the bevel to not break the sharp edge. If the burr not come off despite a lot of honing, a trick is to make a mini bevel by carefully honing in a slightly fatter bevel. When facing the edge line you should not see any reflections in it, since there shouldn't be a surface there to reflect anything at all. This means the axe is sharp.

For more details about sharpening procedure we recommend looking for instruction videos online.

Here is one exaple, a video by the lovely Andy Spoons. He explains how he uses a Tormek to fully restore a damaged axe edge.

Q: How do different types of axes work?

A: Broadly speaking there are three different types of axes, divided by function. They are splitting axes, chopping axes and carving axes. There are different sizes, weights and variants within each type to suit different types of work and given circumstances. The edge and blade shapes vary to fit for different tasks. 

The splitting axe splits the wood fibers along the grain. Edge line and striking face is small to drive the power into the wood instead of spreading it out. The axe hits the wood from above and the edge makes a small grove in the end grain. When the wedge shaped blade drive into the wood, it splits. The blade is slightly concave to first drive fast into the wood and then explode. 

The chopping axe chops the wood fibers diagonal with the grain. Edge line and striking face is medium long to both cut and drive into the wood. The axe hits the wood diagonally and the edge cuts off the grain. When the blades arch just above the edge drive into the wood, it breaks off a big chunk. 

The carving axe cuts the wood fibers along with the grain. Edge line and cutting face is long and curved to slice into the wood. The axe works along with the wood and the edge carves off the grain. When the blades arch just above the edge drive into the wood, it breaks off a shaving. The bevel is flat or slightly concave to allow for working along the grain. 

A carving axe will not work well for splitting big logs or felling big trees but is ok for small things like making kindling and felling a very small tree. A splitting axe will not work well for carving or felling trees. A chopping axe works ok for both carving and splitting, but not near as good as a carving axe or splitting axe.