Sharpening and Caring for Garden Tools: The Bevel Rule, Tool by Tool

A blunt tool is a slow, tiring, slightly dangerous thing. It skids off the wood, makes you push harder, and when it finally gives way it tends to give way suddenly, which is exactly when fingers get hurt. As the RHS puts it plainly, "sharp tools are safer and more efficient to use than blunt ones". A sharp secateur slices a clean cut that heals well; a blunt one bruises and tears the stem, leaving a ragged wound for disease to walk into. Clean, keen tools are kinder to your plants and they last far longer too, so twenty minutes at the bench is some of the best-value time a grower spends all year.

The good news is that most sharpening comes down to one idea, repeated. Learn the bevel rule once and you can apply it to almost everything in the shed. This is a practical guide, so read the safety note, then work through whichever tool you have in your hand.

The bevel rule: the one thing to learn

Pick up almost any cutting tool and look closely at the edge. On one side the metal is ground back at an angle to form the cutting edge: that is the bevel. The other side is flat. The whole of sharpening rests on a single rule: you work the bevel side, and you leave the flat side alone. The RHS is blunt about it: "do not sharpen the flat side", because doing so "will affect the cutting bite" and can ruin the tool.

As you draw the sharpener along the bevel, it pushes a fine lip of metal over to the flat side. That lip is the burr, and it is actually a good sign, because it tells you the edge is now keen all the way along. Once you feel it, you finish the job by laying the sharpener flat against the back and passing it across once or twice, just enough to shear the burr away and leave a clean edge. Bevel side to sharpen, flat side to deburr. That is the whole song.

Secateurs

Secateurs come in two types, and it matters which you have. Bypass secateurs work like scissors: one sharp blade slides past a flat, unsharpened jaw. Anvil secateurs cut by pressing a single blade down onto a flat plate. Bypass are the ones to reach for on live, green wood, because they cut cleanly without crushing; anvil suit dead, dry stems.

Type	How it cuts	Best for	Sharpen
Bypass	Sharp blade slides past a flat jaw	Live green growth, clean cuts	The one cutting blade only, never the bypass jaw
Anvil	Blade presses onto a flat plate	Dead, dry, woody stems	The cutting blade, following its existing bevel

On a pair of bypass secateurs you sharpen the single cutting blade and never the flat jaw it passes. Niwaki give the angle as about 15 degrees, the one sourced figure in this guide, with roughly 10 to 20 light sweeps of a fine stone or sharpener. Work away from you, keep that shallow angle, then flip the blade and pass the flat back once or twice to lift off the burr.

Sharpening bypass secateurs

1. 1

   Wipe the blades clean of sap and dirt.

2. 2

   If they come apart easily, undo the pivot, spray everything with WD-40 and separate the blade.

3. 3

   Colour the bevel with a marker pen: as you sharpen, the bare metal shows exactly where you have and have not touched.

4. 4

   Sharpen the angled side only, working away from you at about 15 degrees, 10 to 20 passes.

5. 5

   Flip the blade and make one or two light passes flat across the back to remove the burr.

6. 6

   Reassemble, set the pivot so the blades meet cleanly, and add a drop of oil to the pivot.

7. 7

   Test on paper: a clean slice means done, a fold and crush means keep going.

Knives and the hori-hori

Garden knives are the tool where you really must look before you sharpen, because they come both ways. Many garden and pocket knives, and one edge of a hori-hori digging knife, are single-bevel, sharpened like a secateur blade: work the bevel, deburr the flat. Pruning knives are often double-bevel, ground like a kitchen knife with two matching angles.

Use a whetstone, pushing the blade up and away from you while holding it at the angle the edge is already ground to. On a double-bevel knife you work both sides evenly, giving each the same number of strokes; on a single-bevel one you work the bevel and then take the burr off the flat. A hori-hori often has a serrated edge on one side too, which you can usually leave alone and simply keep clean. Test on paper when you think you are there.

Spades, hoes and other digging tools

Digging tools do not want a whetstone, they want a flat metal file. A sharp spade slides through soil and slices cleanly through roots with a fraction of the effort, and a sharp hoe skims weeds off at the surface instead of dragging them.

Follow the RHS method: fix the shaft in a vice with the front of the blade facing up, then file along the edge pushing away from you, following the existing bevel and keeping the file flat to it. Do not try to grind a fine, knife-like edge, because a thin edge on a digging tool just chips and folds on stones; a spade wants to stay tough. When the front is clean and bright, turn the tool over and run the file lightly along the back to remove the burr. Flat spades want the file kept flat; a hoe may have a slight slope to its edge, so again, match what is there. Once or twice a year keeps a working tool keen. Gardeners' World note that the humble half-moon edging iron is worth the same treatment, since a sharp one cuts a crisp lawn edge in a single push.

Axes and billhooks

These reward respect, and a light touch. An axe is usually ground with a convex bevel, a gentle curve rather than a flat facet, and that shape is deliberate: do not flatten it out. If it is only dull, skip straight to the finer stones. If it is chipped, start with a coarse stone or file to re-profile, keeping to the curve, then move through finer stones, finish on a strop, and protect the edge with a wipe of oil and a mask or sheath.

Billhooks vary enormously. Some are single-bevel, some double, and the pattern is often regional, so there is no one angle to give. The safe, reliable rule is the same as everywhere else: follow the bevel that is already on the tool. If an axe or billhook is badly out of shape, this is a job many people sensibly hand to a professional rather than risk ruining a good edge.

Shears

Shears are the tool most likely to defeat home sharpening, and there is no shame in admitting it. If they are very blunt, or they do not come apart, sending them for professional sharpening is often the best move. If you are keeping a decent edge topped up, Niwaki's guidance is to lay the flat of the stone against the outside faces only, following the existing bevel, and then give each inside face a single pass to take off the burr. Keep the pivot bolt properly tensioned, because a loose one makes even sharp shears chew rather than cut.

Scythes: honing and peening

A scythe is sharpened in two very different ways, and it helps to keep them straight.

Honing is the frequent one, done with a wet whetstone as you mow. In soft growth you might hone "every 5 minutes or less". The stone is a canoe shape, kept wet in a water-filled sheath on your belt. You hone the narrow top edge first, using the back rib of the blade as your angle guide, with short overlapping strokes along the edge, then give the back a pass to remove the burr. It becomes a quiet rhythm: mow a little, hone a little.

Peening is the occasional, deeper job. Instead of grinding metal away, you cold-forge the very edge with light hammer blows, either freehand on a small anvil or, for beginners, using a jig that controls the angle. Repeated honing gradually rounds the edge over, or "bull-noses" it; peening re-thins and re-forms that edge, and work-hardens it at the same time. Done well, it is what keeps a scythe blade keen for years.

The kit, and grit numbers

You do not need a bench full of stones. A flat metal file covers cultivation tools. For blades, a whetstone or a diamond sharpener does almost everything else. Whetstones come as oilstones, used with a film of oil, and waterstones, soaked in water for a few minutes first; the golden rule is to use the correct lubricant for the stone you own, never oil on a waterstone. Diamond blocks, files and pocket sharpeners cut quickly, last a long time and generally need no oil, and diamond files are especially handy on spades and hoes.

If you buy a whetstone you will meet grit numbers, and the logic is simply that lower means coarser. Niwaki suggest a #1000 stone as the everyday all-rounder, dropping to around #220 to work out nicks and going up to #3000 for a fine finishing edge. A #1000/#3000 combination stone, coarse on one face and fine on the other, is a sensible first and only stone for most gardeners. That final fine pass is what "honing" means: it is the polish that turns a sharp edge into a keen one.

Cleaning and beating rust

Sharpening is only half the story, because a clean, dry, oiled tool stays sharp far longer than a neglected one. The RHS routine is easy to remember.

The RHS cleaning routine

1. 1

   Cultivation tools

   Brush off soil, and hose it if it is really muddy. Then dry the metal with an old towel, which stops rust and keeps wooden handles from swelling. Finish with a thin film of oil wiped over the metal.

2. 2

   Cutting tools

   Clean off sap with a nylon scourer or wire wool and a little WD-40, wipe dry, tighten any pivot, put a drop of oil on the pivot, and store dry.

Rust is really just the result of moisture left sitting on bare steel, so the drying step is the one people skip and then regret. A minute with a towel and an oily rag after each session saves hours of scouring later.

Storage, and the sand-oil bucket

Store tools clean, dry and under cover, hung up on a rack rather than stood point-down in the earth or leaned in a damp corner. At the end of the growing season, give everything a deeper clean, a sharpen and a re-oil before it goes into winter storage.

Disease hygiene

Dirty blades spread plant disease, and some are serious: the RHS specifically flags things like Phytophthora root rots, bacterial canker and box blight as problems that spread on unclean tools. Good hygiene is genuinely part of keeping a garden healthy.

For a general clean, brush cultivation tools free of soil at the spot where you used them, so you are not carrying soil-borne trouble around the plot. To disinfect blades, the RHS suggest a proprietary disinfectant such as Jeyes fluid, Citrox or Propellar: apply it, leave it the stated 15 to 20 minutes to work, then wipe it off, dry the tool and oil it. Disinfect the brush, the cloth and even your boot soles as well, since they carry spores too. When you are pruning diseased material, wipe or dip secateurs and knives between plants, and certainly between cutting out disease and touching healthy growth.

Wooden handle care

A neglected wooden handle goes grey, rough and splintery, and eventually snaps. It is easily prevented. Gardeners' World advise sanding a rough or splintering handle smooth, then treating it with boiled linseed oil: brush it on thinly rather than sloshing it about, let it soak in, ideally overnight, and it will bring up the grain and keep the timber supple. The end of the season is the natural time to do it. Tung oil does much the same job if you prefer it.

Sharpen little and often

The single best habit is to sharpen little and often, rather than waiting until a tool is hopeless. A quick touch-up on a keen edge takes seconds and keeps it keen; rescuing a badly blunt one is a proper job. Learn the bevel rule, keep a file and a combination stone within reach, wipe and oil your tools before they go away, and they will serve you cleanly for decades. And when something is genuinely past a home touch-up, badly chipped, bent or worn out of shape, a professional sharpener is cheap next to a new tool.