Shaping and sharpening an axe requires knowledge and practice. Nothing could be more important to using an axe effectively and safely. A properly sharpened axe will cut more quickly and cleanly, and the edge will be more likely to bite into the wood than glance off and strike nearby objects.
Shaping is done infrequently, usually to restore an old tool, and requires the removal of a significant amount of metal.
Sharpening is done regularly, prior to a day of axe-work or in the field, and is more of a retouching of the edge.
If you have an unsharpened, corroded, or damaged axe, the edge will need to be shaped before it can be sharpened and used.
The workhorse tool for shaping edge tools such as axes is the mill file. Mill files remove metal relatively quickly without producing too much heat, and with the long flat surface it is easier to maintain a consistent edge angle. Hand shaping your axe with a metal file can be rewarding and practical, but it can take time to get it right.
To speed up the process, many people use bench grinders. Aggressive grinding devices such as bench grinders (pictured) are generally frowned upon, for legitimate reasons, as they can overheat and destroy the temper of the axe head, rendering the metal too soft to be an effective tool. Although water-cooled wheel grinders can prevent overheating, the nature of the wheel tends to give a hollow grind which is not as strong as a flat or convex grind.
If grinding an axe, most experts recommend using a pedal-driven grindstone which is continually kept wet by the application of water during the rotation of the wheel. These old-fashioned grindstones are hard to find and expensive, and thus not practical for most people.
To prepare an axe for shaping, first check that the head is securely fastened to the handle. It is preferable to remove any visible rust with steel wool, a rust eraser, or fine grit sandpaper before commencing the shaping of the head itself.
We strongly recommend the use of leather gloves when shaping or sharpening any cutting tool.
Once inspected and cleaned, place the axe in a vice to secure it tightly, making sure that the cutting edge is parallel with the floor and level. Use a mill file to shape the edge, pushing the file toward the edge you are sharpening as opposed to filing from behind the edge.
Most professional axe-men place both a primary and secondary bevel on their axes. To effectively reshape an axe, one must not focus wholly on the edge alone, as this sharpened edge quickly widens to a much thicker head that resists further penetration. Thus, a primary bevel is established well up the axe head to facilitate deep cuts, while the secondary or edge bevel is slightly blunter to prevent the edge from folding, chipping, or dulling quickly.
A sharpening gauge, which is used to check the angle and shape of the cutting edge, can be fashioned from carboard or other materials and used as a template.
When shaping the axe, start with the secondary edge, which is the cutting bevel of the axe. By starting with the secondary bevel, the primary bevel can be filed down to it later. The bevel angle of the secondary bevel usually ranges from 15-20 degrees per side depending on the hardness of the material being cut (Harder wood, blunter edge angle). Use the file to remove all irregularities from the cutting surface and take pains to maintain an even width to the bevel along the entire cutting surface.
File for multiple strokes on one side until a burr, or raised ridge, of metal appears on the backside, then flip and file the other side, continually checking the general shape with the gauge. If your axe has a double-bit, many professionals leave one side more blunt for rough work. Once the shape corresponds with your gauge template, and the secondary bevel is consistent in width and angle on both sides, mark the bevel edge with a magic marker.
Once the secondary bevel has been marked, the primary bevel can be formed. Proper shaping involves creating a fan shape with the file emanating from the center of the edge to a distance back from the edge of 2 to 3 inches, thus thinning the entire profile of the axe head. Most primary bevels are set around 10 degrees on each side, tapering them so as to leave the metal about 1/8th of an inch thick where the prmary bevel meets the secondary bevel.
Once the general shaping of the primary and secondary bevels is complete, or if the axe head is in good condition and just needs to be retouched, the edge can now be honed and polished to a working edge.
The easiest method of putting a polished, professional finish on an axe edge is by using a belt grinder (pictured below-right). Belt grinders will remove the file marks and sharpen the edge without overheating the metal unnecessarily. Inexpensive belt grinders can be found at Harbor Freight, among other locations. Unfortunately, the belt grinder is not transportable, so touching up the edge while working in the field must be accomplished with a stone.
Once in the field, sharpening is done with a stone or diamond hone. We carry a number of sharpening tools here. Repeated passes of the sharpener will further refine the edge. Applying oil helps to float the small metal particles removed during sharpening, keeping them out of the holes in the stone that create the friction needed to continue to refine the edge. Other stones work "dry," such as the below canoe file, and can be carried in the pocket and do not need oil.
Stropping with a leather belt after using the whetstone is an effective way to remove the wire edge or burr that develops, and puts a fine finish on the axe.
A properly sharpened edge should not reflect light and should not have a burr of metal along the edge, which will fold or crumple when the axe is used. If the edge is pressed to your thumbnail, it should bite into the nail and stay in place, not slide.
Test the new edge out by lightly striking the axe on some soft wood, then inspect the edge to make sure that no major folding or crumpling has occurred. If major imperfections have formed, the bevel angle may need to be made more blunt for the material you are chopping. A diamond hone or field stone should be kept on hand for touching up the edge while out working in the field.
To prevent the axe from sticking in wood, waxes or oils such as Waxilit, Boeshield, or linseed oil may be applied to the head. Some experts suggest gun oil, which forms a seal on the axehead.
Besides reducing friction when chopping, oiling or waxing your axe protects it from rusting, especially when not in use. Make sure to wipe away all excess moisture after each use, and be sure to store your axe out of the sheath to prevent moisture being trapped inside the sheath and rusting the metal.