Sharpening garden tools and safety might seem to be at odds with each other, as a sharp edge can do a lot of damage to flesh. But in fact the opposite is true: a blunt blade will need more force to make it cut and is more likely to slip and hurt someone, whereas a sharp blade will slice more easily through plant material.
Here, we focus on the smaller hand tools used in the garden and avoid larger tools like saws and motorised tools. In any case, saws and the cutting surface of other larger tools are being designed to be disposable these days. In consequence the places where you used to be able to take them for sharpening are disappearing.
Getting Ready to Sharpen
Small hand held tools like knives, secateurs and cutters can be sharpened on a sharpening stone, also known as a whetstone, available from hardware stores, DIY shops and garden centres. With small tools place the stone on a bench at a comfortable working height and if necessary knock a couple of small bits of wood into the bench to help keep the whetstone in place.
The blade should be cleaned first, removing muck with a cloth and then taking off any rust with wire wool. The basic idea is to pass the blade over the stone again and again, pressing down and lubricating the stone with oil to help the blade move more easily. The critical point is to get the blade at the right angle and keep it at that angle throughout the process.
Check Your Blades Out First
A blade will usually have a flat side and a tapered side. Sharpen the tapered side first, at the same angle, as far as you can tell, as the original taper. Then turn it over onto the flat side and pass that over the stone as close to flat and parallel with the stone as you can. This will remove any burrs from the first sharpening pass.
With secateurs and other cutting tools, closely inspect the cutting edges before you begin. Many of them rely on the tapered edge passing a blunt blade rather than having two cutting edges and if this is the case, only the tapered side of the blade should be honed. If you taper the straight side of the cutting blade the two blades will be more likely to separate and pass each other with the plant material between them rather than being cut.
Many whetstones are flat and can be used for knives and shears but might be tricky on curved blades like secateurs. It is possible to buy curved whetstones but these are harder to use and require a lot of practice. With curved whetstones it is more usual to hold the tool and pass the sharpening stone across the face of the blade, always sweeping away from the body. A curved whetstone like this can be used for larger curved blades like scythes and cylinder lawnmower blades (but be VERY careful with those).
Digging tools like hoes and spades can benefit from sharpening as well as cutting tools. Hold them upside down and sweep the whetstone across the face of these tools and with hoes make sure you only hone the upper surface.
After sharpening make sure the tools are given a final wipe over with an oily cloth to prevent rust build up and store them well away from any inquisitive fingers. Larger tools like shears, scythes, hoes and spades should be hung up, with the blades uppermost if at all possible.