Written by the great folks at Gransfors Bruks ‘How to sharpen an Axe’.
The sharpening of an axe is done in several steps depending on how worn down the axe head is.
1. Major nicks and damage can be filed down with an emery wheel but do not overheat the steel or it will lose its temper. Cool often! However the easiest method is to use a fine-toothed flat file. Make sure that the edge retains its original shape file the same amount on each side and along the whole edge. The whole bevel face should be in contact with the wheel/file if it is a straight bevel face.
2. Minor damage and normal wear can be tackled on a wet bench grinder or with a coarse handheld whetstone to re-establish the sharpness of the edge. Remember to always keep the original shape of the edge. If you have an axe with a straight bevel face: place the whole bevel face against the grindstone. When grinding on a rotating bench grinder first place the rear part of the bevel face on the grindstone and then angle the edge until the whole bevel face is against the stone. The choice of grinding with or against the rotation of the grindstone is a matter of taste: Going against it produces less of a burr. Going with it avoids the risk of digging into the grindstone.
Stand steady with one foot placed beside the grinder and support yourself with the axe against a supporting stay on the grinder or with your elbow against your hip. Move the axe slowly back and forth during grinding so that the whole edge is evenly ground. Also grind evenly over the breadth of the grindstone otherwise it will soon become warped and difficult to use. Do not leave water in the grinders drip cup as this reduces the quality of the stone. An alternative to the rotating grinder is a coarse handheld whetstone (axe stone).
3. Finally you need to hone the edge to remove the burr or feather edge. The feather edge occurs when the very tip of the edge has become so thin that it bends up. The feather edge is only a few tenths of a mm long but can clearly be felt if you slide your fingertips carefully down to the edge. The honing requires first a coarse then a finer whetstone. Moisten the whetstone with water (mainly for clay and sandstone whetstones) or oil (mainly for carborundum or Arkansas whetstones) e.g. honing oil or sewing machine oil.
Move the whetstone along the edge in a rotating motion. Hone along the edges of the whetstone rather than in the middle to avoid gradual cupping of the stone. Turn the axe frequently and hone both sides to remove the feather edge. Wipe off the whetstone occasionally so that the burrs do not damage the edge. Also give the whetstone a thorough wipe down before putting it away.
4. To make the cutting edge even keener it can be stropped against a length of leather after honing. Run each stroke away from the cutting edge.
The design of the axe head is adapted to its area of use: hardwood demands axes with a fairly thick bit and a rounded bevel face while axes with a more pointed edge are good for cutting softwood. Axes with a thin straight edge are good for carving with while axes with rounded edges are good for chopping in the forest. Broad axes and carving axes have many different edge designs depending on their use and whether the user is right- or left-handed.
1: For cutting hardwood or frozen wood
2: For cutting softwood
3: For carving. Angle 25º 30º
4: Wrong grind
A: Curved edge.
Stronger than straight edge. E.g. Forest Axe and Wildlife Hatchet.
B: Straight edge.
For carving. E.g. Carpenters Axe
C: Wrong grind and dangerous.
Always keep the original shape of the edge even after grinding and sharpening. A wrongly ground axe slips more easily. Grind equally over the whole edge and on both sides!