Why a sharp edge is the whole job

A blunt billhook is not simply slower to use. It is the tool most likely to hurt you. A keen edge bites into hazel, willow or ash and stops where you put it. A dull one skates across the surface, slips off a knot and carries on towards your shin. In a day spent coppicing a stool or laying a hedge, you might make two or three thousand cuts, and every one of them is a negotiation between the steel and the wood. Sharpen properly and the negotiation goes your way.

There is also the matter of fatigue. A billhook that needs three strokes where one would do will leave your forearm and shoulder aching by mid-afternoon, and tired hands make mistakes. Sharpening is not a chore bolted onto woodland work; it is part of the work, the same way mending a glove or re-handling a rake is part of it.

Know your bevels before you touch the steel

Almost every edge in the woods is a simple flat bevel, and your first job is to find the one already there rather than invent your own. A billhook usually carries a single bevel on the upper or outer face, with the underside left flat. That flat underside is what lets the hook slice cleanly through a rod without wedging, so do not go at it with a file and round it off. The bevel angle on a working billhook generally sits somewhere around 25 to 30 degrees, stouter on a Yorkshire pattern used for heavier hedging and finer on a lighter Kentish or Suffolk hook.

Axes vary more. A felling axe wants roughly 25 degrees at the bit, a splitting axe or maul nearer 30 because it is being driven into reluctant timber, and a small carving axe can safely go down to 20. A slightly convex edge, built up gradually by file and stone, is stronger than a perfectly flat one and resists chipping when you catch a knot or a hidden nail in a fence post.

Filing: restoring an edge that has dulled or rolled

When the edge has gone properly, a file does the heavy work. A 200mm double-cut flat file is the standard choice, though a mill bastard file cuts a little faster. Clamp the work so both hands are free and the blade cannot move. For a billhook, gripping the handle in a vice with the blade horizontal and the bevel facing up works well.

• Match the existing bevel angle and lock your wrists so the file stays at that angle throughout the stroke.
• Use a draw file stroke, pushing the file diagonally across the bevel rather than straight along it. This keeps the bevel flat and avoids digging in.
• Count your strokes on each section and repeat the same count on the other side. Consistency matters far more than force.
• Feel for the burr by drawing your thumb across the bevel, never along the edge. When a fine wire edge turns over along the whole length, the bevels have met.
• Do not use an angle grinder unless you are very experienced. It is far too easy to draw the temper out of the steel and ruin a good tool.

Whetstones and honing

The file leaves a coarse, toothy edge. That will cut, but it will not cut well for long, so follow it with a stone. A combination waterstone around 1000 and 6000 grit, or a fine India oilstone, will serve for everything from a billhook to a small axe. A diamond plate is useful for flattening a dished stone and for quick work on a badly damaged edge.

Keep the stone wet or oiled according to its type, and keep the angle identical to the one you filed. Work in overlapping passes along the bevel, alternating sides every few strokes, gradually reducing pressure as the edge refines. Finish with two or three light strokes flat on the underside to remove the burr, then a couple more on the bevel side. The edge should end up bright and uniform along its whole length, with no dull patches near the tip or the base of the blade.

Stropping through the day

A strop is the most underused tool in British woodland kit. A length of leather glued to a flat board and charged with a little fine polishing compound will realign an edge in twenty seconds and keep you cutting for hours. A piece of flat hardwood with compound works nearly as well. Take ten strokes a side, pulling the blade away from the edge so the leather does not slice.

The habit to build is little and often. Two or three strokes on the strop every half hour of steady cutting is worth more than an hour of filing on a Sunday evening. Carry a small puck stone or slipstone in your pocket for the axe, and a round file or fine slipstone for the inside curve of the billhook, which occasionally needs a light touch to keep the hook true.

Kit and habits worth keeping

• A 200mm flat file in a leather sheath, kept dry and lightly oiled.
• A combination stone or oilstone, and a small slipstone for curved edges.
• A strop board and compound, kept in the tool bag rather than the shed.
• A rag and a tin of light oil to wipe blades before they go back in the sheath.
• A sheath for every axe, and a rack or dry box at home so nothing sits on damp concrete.

Ten minutes of attention at the end of a working day keeps an edge keen for weeks rather than days, and a well-kept billhook or axe will outlast the person swinging it. Learn the bevel on your own tool, hold your angle, strop often, and the wood will tell you plainly that you have got it right.