Sharpening Garden Tools

A dull tool is always inefficient. Where a sharp axe bites into wood cleanly, a dull one can ricochet off the wood and cause a serious injury. A dull lawn mower crushes the blades of grass, causing the tops to quickly wither and turn brown. A dull hoe bounces off hard ground rather than sinking into it. Keeping your tools sharpened and using them carefully will make your work much easier and get the job done better and more cleanly

What makes a tool sharp? When its cutting side is beveled to form a keen edge, it is sharp. The lower the angle of the bevel (that is, the narrower it is), the sharper the tool will be. But the edge of an extremely sharp tool is more likely to get nicked and bent, since it has less metal behind the bevel. Thus, the degree of sharpness desired depends on what use the tool will be put to.

Since tools are manufactured with the ideal bevel angle already ground on the basis of intended use, the first rule in sharpening is to follow the existing bevel. The second rule is to remove as little metal as possible; this makes the tool last longer. Sharpening wears down tools much more than does normal use. So to make your tools last as long as possible, remove as little metal as you can each time you sharpen them.

To keep all your tools sharp, you need the following equipment: A vise, a bench grinder, an electrical drill, a few different types of files, and two or three different types of whetstones.

Bench Grinders are electrical motors that turn abrasive wheels. Many have an abrasive wheel mounted on one side of the motor and a wire brush mounted on the other. The wheel sharpens and the brush removes rust.

The grinder sharpens faster but less precisely than hand-held files or whetstones. It also removes metal the fastest and thus produces the most wear. Therefore, be selective when choosing tools to be sharpened by this method. The grinder can quickly shape up badly nicked or dulled tools, such as axes, mattocks, and rotary mower blades. Thereafter, keep them sharp via regular touchups with a file or whetstone. When you use a bench grinder, always wear goggles to protect your eyes from flying particles.

Sanders: If you have an electric drill with a grinding disc on it, you can also use it to quickly shape and sharpen a tool. Many hardware stores sell coarse grinding discs for drills, specifically for sharpening tools. These discs, impregnated with a 24-grit aluminum oxide, will sharpen nicked or dull tools, such as hoes, axes, and mattocks.

Files remove metal much more quickly than do whetstones. This makes them best on such tools as spades or hoes but not on finer tools such as jackknives or pruning shears. The cutting edges or serrations on files come in two basic patterns: single cut, known as a mill file, with parallel serrations, and double cut, with two serrations that run at opposite angles to form a checkerboard pattern.

Single-cut, or mill, files are the best for garden tools. Double-cut files are coarse, remove metal quickly, and remove burrs from the metal. Mill files remove less metal. Therefore, they do a much better job of sharpening. Since files are designed to be pushed, not pulled, be sure to release all pressure on the backward stroke. Also, never use a file without a handle. The tang (the pointed end of the file)is designed to fit into a wooden handle. Serious injury could result from using the file minus the handle.

Files are graded according to their coarseness. Coarse is the roughest grade, followed by bastard, second, and smooth grades. The coarseness also has to do with the length of the file. A 14-inch bastard file is coarser than an 8-inch bastard file because its serrations are more widely spaced.

Since files are inexpensive, you may want one of each grade in several different types and lengths. However, a flat 8-to-10-inch bastard file and a flat 8-to-10-inch second file will handle most of your work.

For sharpening saws, however, the files must be fit to the size of the saw’s teeth. For sharpening pruning saws, you need a knife file. For sharpening chainsaws, you need a round file. Because saw teeth vary so widely in size and number per inch, it’s hard to determine which file best suits your saw. The best method is to take your saw to a saw-sharpening shop or a good hardware store and ask someone there to help you select the proper file.

Files themselves should not be sharpened. However, they do need to be kept clean by periodic scrubbing with a wire brush to remove metal particles between the serrations.

Whetstones are used to hone fine edges or metal that is too hard for the file, particularly on knives, shears, scythes, and axes. Whetstones come in three categories:

  • Diamond whetstones (also called diamond files)
  • Stones that are oiled (oilstones)
  • Stones that are not (drystones)

Whetstones usually come in any of three shapes: flat, round, or long and tapered. Each has a specific use.

Diamond whetstones use diamond dust to cut. The dust is imbedded in a matrix that may be continuous or in the form of dots imbedded in metal or plastic. Diamond whetstones wear very slowly, so they last a long time. They don’t require oiling because the diamond dust is too fine to plug with metal filings. They usually come in three different grits.

You cut faster by applying more pressure, and apply a fine finish by stroking lightly. Because the matrix is lighter and stronger than stone, they are often made in pocket or folding formats to be carried around.

Drystones have a surface that crumbles away as you use it; thus they constantly renew themselves, but also wear out much faster than oilstones. Generally, the drystone is carried around for on-the-spot sharpening of tools like jackknives.

Oilstones, which are used more commonly, must be kept oiled while in use. Otherwise the metal particles that accumulate from the grinding of the tool will clog the stone’s surface, covering it with a glaze that keeps the stone from cutting. When the stone is properly oiled, however, the film of oil floats away the metal particles, thus preventing the stone from clogging.

When you buy a new oilstone, put it in a shallow pan of lightweight household oil for a day or so and let it soak up as much oil as it can. This treatment will ensure that when a few drops of oil are placed on the surface, they will stay there rather than soaking into the stone right away.

Before each use, put a few drops of oil on the stone. After each use, wipe the oil off. Because the stone is oily, it gathers dust easily, so keep it in a covered case in your workshop.

The flat whetstone (often called a bench stone because it is kept handy on the work bench) is the first choice for general use. It is usually an oilstone. Most often it has a coarse side for sharpening an edge quickly and a smooth side for fine honing. Normally, the stone is kept stationary, and the item to be sharpened is passed back and forth over it.

The round whetstone, which also has coarse and smooth sides, is held in the hand and passed over the item to be sharpened. Its most common use is for sharpening axes and hatchets.

The long, tapered abrasive sticks or rods, which come in a variety of sizes, can be used to sharpen sickles, scythes, scissors, and shears. These sticks or rods generally are drystones or diamond files.