If you have a lot of fences to build and maintain, you can make the job easier by buying or renting a posthole digger. In selecting a posthole digger, consider these factors: Your type of ground, the depth of hole you’ll need, how often you’ll use the digger, and the extent of your own strength.
If you need holes up to 2 feet deep, the clamshell digger is the best general-purpose tool. Auger-type diggers work for holes of any depth, but because they are less strong than the clamshell, they are less effective in hard, rocky soil. If you will need to dig many holes, think about renting a gasoline-powered auger. Whichever type you select, look for good steel blades and good-quality handles of straight-grained ash or hickory.
A crowbar is a good companion tool for a posthole digger. It breaks or loosens rocks and soil that are too tough for a posthole digger. The loosened soil can then be lifted from the hole with the posthole digger.
Among home gardeners, the clamshell digger is the most common type. It works with a scissor action. The two handles are about 4 feet long, and the blades add another 9 to 12 inches. When you push the handles together, the two curved blades open. Jam the digger into the soil; then pull the handles apart. This closes the blades around the earth so that you can lift it out.
Another type of posthole digger—essentially an earth auger—has two stationary blades on the end of a steel rod. The tips of the blades are bent inward at right angles and slightly offset from each other. The rod is twisted by the handle on top and the blades screw themselves into the ground. When they are filled with earth, lift out the digger, remove the soil, and repeat the process. This type of digger is effective in soft soil only, not in hard or rocky soil.
Powered augers are also available. A two-man version is gasoline powered. Another type attaches to a jeep or tractor.
A posthole digger made in Canada combines a fixed blade and a movable blade. The fixed blade digs into the soil; the movable blade, operated by a lever on the handle, closes on the fixed blade to seize the soil.
Before storing any posthole digger, clean and oil its blades (particularly the scissor mechanism on a clamshell digger). This will keep the tool in good working condition.
Extensive use will make the blades of a clamshell digger become dulled, bent, or chipped. When working far from the workshop, it’s wise to keep an 8-inch bastard file in your pocket; you can use it to periodically touch up the blade ends. File only the inside of the blades, and keep the bevel at between 60 and 80 degrees—this will keep lots of steel behind the edge to help prevent it from bending or breaking. Regularly check the bolts and nuts holding the blades to the handle.