Give me 6 hours to chop down a tree and I'll spend the first 4 sharpening the ax.
U.S. Forest Service's manual, One Moving Part: The Forest Service Axe Manual notes that an ax must do three things to cut efficiently:
Guidelines shown below are for Included Angles (α). Notes are also available on a different web page for Micro / Secondary Bevels.
Sharpening axes on the Tormek uses the Tormek SVA-170 Ax Jig. Alternatively, an angle grinder can be used with a 120 grit flap disc.
|Ax Type||α||Secondary Bevel||Notes||
|Soft Wood||Hard Wood|
|General||20°||25°||2° - 5°||This is a guideline. Exact angles are not required.||
|Carpenter||20°||25°||Grind the edge so there is a longer side facing the wood.|
U.S. Forest Service
The U.S. Forest Service's manual, One Moving Part: The Forest Service Axe Manual, recommends these angles. This manual also recommends a convex grind.
For double-bit axes, this manual also recommends
The Forest Service's preferred method is to leave one edge thinner and sharper and the other edge thicker so that it doesn't have as sharp a cutting angle. Ax nomenclature refers to the thinner, sharper edge as the "keen" edge and the thicker edge as the "stunt" edge. The difference in cutting edges allows axmen to use the proper edge for the type of wood they cut. The keen edge sinks deeper into wood that is free of knots and allows the axman to remove bigger chips. The stunt edge is better in harder, dense wood, such as tree limbs or knots, and allows the axman to work without bending, chipping, or otherwise damaging the cutting edge of the ax. (pg. 15)
There are some who recommend that the overall grind be convex (see also, An Ax to Grind: A Practical Ax Manual from the U.S. Forest Service). I have found that using a secondary bevel removes that need.
High speed bench grinders are NOT recommended. The U.S. Forest Services says to not use them at all.
It is too easy to take the temper out of the blade, and the user will get very poor service from the ax. If the sharpener does not have access to a wet grinding system, then a file or stone approach should be used (as outlined in the manual noted below). Angle grinders with flap discs don't cause such a build-up of heat if used in a limited fashion (e.g., for sharpening and not shaping the angle).
When sharpening axes, use the vertical position with the grindstone rotating towards the blade. This keeps the SVA-170 properly aligned to the grindstone. (If you use the horizontal position, the grindstone will tend to pull the axe away from the jig.) Also, this position sharpens faster.
Be sure to remove all caked-on dirt. A wire brush or putty knife can be useful for this. A well-kept tool will last your lifetime, and will still be usable by your children (and maybe your grandkids).
Sap can be removed using a solvent. Acetone works well, but be sure to wear protective clothing as this is not kind to your body, and be sure the area is well ventilated. After using any solvent, be sure to apply a thin coat of camellia oil to the axe.
If the axe was exposed to any diseased plants or soil which is infected with pests, give it a quick wash in diluted bleach (1 part bleach to 8 parts water), and then rinse with plain water. Be sure to dry afterwards, and apply a thin coat of camellia oil.
If the axe's poll has gotten mushroomed out, it needs to be cleaned up. Leaving the mushroomed surface will make for danger when using the axe, just as with cold chisels.
Axes often get stored for a while after sharpening, so it is recommended to oil the sharpened surface with camellia oil. (Indeed, all unpainted surfaces would benefit from this.)
I like the spray bottle of camellia oil sold by Tools for Working Wood. Some advocate using boiled linseed oil (BLO), but BLO often has heavy metals or other bad chemicals added for drying agents, and these are not good for you to handle, nor would they be good for the plants on which you'll use this tool.
Petroleum jelly is another option for coating the surfaces for long-term storage.
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