There's no question, an earth auger can save you a huge amount of time during a large project that requires many post holes. Unless you're digging only a few holes, a power auger is the only way to go. An auger can move your daily post digging number from 15 to 40+, not to mention avoiding the brutal work of digging by hand. Keep in mind, however, that digging with an auger can still be difficult and in an ideal situation, you'll have at least two men doing the work to help manage the high torque these machines run with.
Before you begin digging with any power auger, remember to use safety gear and to check for power, phone, and water lines to ensure that digging is as safe as possible. Do a good job of measuring and lining out your holes, while you're checking for hazards, so there is no need to modify your plans during the middle of the project.
Generally, you'll be looking to use either a one-man power auger or a two-man earth auger, either way, check that the auger and auger bit are capable of matching the width and depth that you require for your project. Standard auger drills come in sizes ranging from 4 inches to 12 inches and anywhere from 36" to 48" in depth. Extension rods are also available if you need them; check to make sure the auger bit and extension rod you choose are compatible with the auger power unit. Larger diameter and length may be tougher to handle, consider the man-power you may need to work effectively throughout.
Operating an auger can be hard work, so prepare yourself for the amount of torque that will be running through this machine--Brace yourself! It's best to dig primer holes with a shovel or post hole digger to allow for proper alignment. Once you begin moving soil, you'll get a feel for the power of the machine. For best results and the most efficient work, dig a few inches at a time and then throttle back to remove dirt. An entirely submerged auger drill is hell to remove, so as much fun as it is to drill the depth of the entire bit all at once, restrain yourself; unless you plan on entering the World's Strongest Man competition! When using an extension rod to dig, dig first with the non-extended auger drill to ensure optimal control. Also, if all you need is a few more inches it's often easier to dig the final part of the hole by hand.
Final tips:
Dig a pilot Hole. This allows for an easier start with the power auger, by giving you somewhere to rest the unit while you start it.
Clear the hole often. Clearing the hole will prevent you from having to dig your auger out of a 3-foot pile of dirt.
Advance slowly. Advance the throttle slowly while you start to ensure your hole is straight.
Turn the engine off. Turning off the engine while you dig out dirt or move to the next hole will reduce the risk of accidental injury.
Never Start with extensions in place. Controlling a six-foot auger bit at head-level reduces your control, increases risk of injuring, and is just downright dumb. Start with your normal auger bit and ad the rod once the hole is beyond the drill's depth.
Remove powerhead to dislodge augers. If your bit gets stuck, be sure to remove the powerhead before attempting to dislodge your drill. Use a pipe wrench to turn the auger out of it's hole.
If you have specific questions or concerns about augers or digging post holes, feel free to leave your comment below!
