A Common Thread
The Right Auger
Attachment Should
Help You Put Holes
in the Ground — Not in Your Pockets

By Nick Zubko

When you’re young, it doesn’t get much better than digging holes in the backyard — the bigger the better. But once you grow up and you have a business to run, what might once have been your favorite activity loses its novelty pretty fast. All of a sudden, digging holes starts to look more like what it really is — a whole lot of hard work.

The bulk of landscaping, construction and even agricultural applications involves digging rows and rows of holes in the ground on a regular basis. As such an important part of their daily operations, contractors long ago began
looking for easier and quicker ways to get the holes in the ground — without doing what used to be the best part.

For years now, operators have found that fitting an auger attachment to their favorite piece of compact equipment is often the best solution. These auger implements can do wonders for a crew’s productivity in a variety of environments — from confined construction and landscaping work to agricultural and nursery situations. The tools provide a perfect solution to digging the right sized holes in rapid succession, whether it’s a series of small, precise postholes to set fence posts or larger holes to plant trees, bushes and shrubs.

Auger attachments range in price from $900 to about $2,600 and are relatively straightforward in design. But there are still a few key points that potential customers should be familiar with before they start digging on their next job — and maybe more importantly, before they start digging into their pockets.

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Digging In
Depending on the market, auger attachments are linked to a piece of compact equipment in one of two ways — via the hydraulic system of a skid steer, mini excavator, compact backhoe loader or compact utility loader, or through the PTO (power take-off) shaft on a compact tractor. This is determined by the inner working of the auger drive — the gearbox that holds the bit, also called the “power head.”
A variety of auger power heads are designed with different methods of reduction to accommodate wide ranges of applications and ground conditions. The three main types of power heads include direct drive, chain reduction drive and planetary drive. The most basic and inexpensive types of power heads are called direct drives or PTO-driven units, which use hydraulic drives with no external reduction.

“A direct drive [power head] is essentially a three-point unit designed to run on a 540-rpm PTO shaft located at the back of a standard tractor,” explains Ron Grimstad, product manager for CEAttachments Inc., an attachment distributor out of Cedarburg, Wis. “A PTO driveline connects the tractor PTO shaft to a gearbox and the auger hangs from the output shaft. Those drives are catered to agricultural applications, or some landscaping — where you don’t really have a lot of holes to drill.”

Hydraulic auger drives (chain drives and planetary drives) are used more by customers who dig holes as a business, using them much more frequently to drill a variety of different hole sizes. Chain reduction drives incorporate a simple sprocket and chain leading into the output shaft. While they are the most economic option for a hydraulic attachment carrier, chain drives also have their drawbacks. They are typically more prone to stretching and since the drives run dry, the chain and sprockets are subject to substantial wear. Typically, these factors lead to increased maintenance down the road.

Planetary auger drives, on the other hand, are smaller, more compact units, with the hydraulic motor operating through hydraulic oil contained in the gearbox. Also, the gears on a planetary drive typically last longer than a chain and sprocket. And in contrast to the rectangular design of a chain drive, planetary drives are made with a cylindrical case that usually fits inside the hole being bored, providing a slight advantage in digging depth. Planetary drives are seen as the more durable of the two auger drives, but they are also more expensive — so manufacturers say there is a legitimate market for both designs.

“Chain drives are really made for the less-frequent user,” Grimstad says. “They are a little lower cost and it’s also a good option for rental houses, because maintenance on them is not as exacting. If you break a chain, it’s easy to fix, whereas if you break a planetary gearbox, it’s more expensive and more difficult to fix.”

But according to manufacturers, which type of auger drive you choose really depends on what type of customer you are. “If you’re a contractor who makes your living with it, then you probably are going to want a heavy-service planetary drive,” notes Alan Jones, sales manager for Belltec Industries Inc., an auger drive manufacturer based in Belton, Texas. “But if you just need to pop a few holes every now and then — and it’s not something you are going to use on a daily basis — cost will typically become more of a factor and you might start looking at a chain-driven auger.”

Customers are also faced with balancing the amount of torque they need with the speed at which the bit turns, which is measured in rpm. Both torque and speed depend on the amount of reduction, which differs slightly with every manufacturer. Inherently, augers require a tradeoff between torque and bit speed — which comes down to what type of work you are doing and how fast you need to do it.

“If you are in hard, rocky soils conditions, the slower you can spin that bit with more power and pressure, the better and easier it is going to be to get through those harder, rockier conditions,” notes Mike Amerman, attachment product specialist for Bobcat Co. “If you have a fast bit and you are just trying to spin it real fast with low torque, that drive is going to stall out instantly in those types of situations. Then it’s the responsibility of the [dealer] to recommend the appropriate attachment for each type of situation.”

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Auger Bits
Just as important as choosing the appropriate type of power head to fit your needs, there is also a wide variety of auger bits available on the market today. Auger bits range in size from 4 to 36 in. and in price from $170 up to $900 for a standard auger bit, while prices can range higher for heavy-duty carbide teeth, rock bits, etc.

“A standard auger bit will be a dual-flighted bit and will have essentially flat cutting teeth with what is called a fishtail center point, which are primarily used for removing soils,” explains Grimstad. “Then if you have stratified rock — whether it’s shale or limestone — you move to a rock and frost bit, which actually has carbide rock teeth. The other obvious bit selection would be the tree and shrub — which is usually a tapered, cone-shaped bit used for making sink holes for plants.”

In tougher ground conditions, most auger manufacturers supply two or three earth-style bits, depending on the type of soil conditions. Rock bits are essentially the same, but the teeth and the thickness of the flighting vary. A standard rock bit has flighting that is 3/16- or 1/4-in. thick, whereas heavier bits use flighting up to 3/8- to 1/2-in. Like anything else, making sure you use the right tool for your application is critical for success.

“The flighting is really the main difference between auger bits, referring to how the angle or pitch of the flight changes to help drive the auger into the earth,” explains Amerman. “For the most part, the type of material and the thickness of the metal stays the same, whether you have a light-duty bit or a rock bit. In addition, rock bits will typically have carbide teeth on the bottom on the auger bit, which allows them to get through different fragmented rock, softer asphalts or harder soils.”

Manufacturers suggest you get a good idea of the ground conditions you will be digging in, then ask your equipment dealer what types of bits work best in those conditions. Oftentimes, an experienced dealer should be able to match up the right bit specifications just by their knowledge of the ground in your area.

“When a customer calls up from Louisiana, he’s not going to need the heaviest-duty unit in the line,” notes Jones. “Bit-wise, you’re always going to direct that
customer to a dirt auger, because a rock auger is not what he needs. Now if someone calls in from west Texas, Kansas or somewhere else that has a lot of rock, you immediately know they are going to need the heavier-duty bit, because a light-duty unit is not going to do the job or might not hold up.”

In addition to flighting, auger shoppers also need to know what kind of shaft their auger drive unit accepts — round, hex or both. They also need to determine the
output shaft diameter, because there are a multitude of diameters available on the market. Some manufacturers offer 2- or 2 1/2-in. round or 2-in. hex. Hex bits make the auger ride on the output shaft, rather than just the bolt. Round bolts place all the torque directly onto the bolt, so some manufacturers say hex bits can withstand more arduous use than a round-shafted bit.

“Typically, round drive bits tend to be less expensive” notes Grimstad. “The hex drive tends to be for the guy who is going to be sinking a lot more holes and is willing to pay a 10 or 15 percent premium for the bits. The only thing keeping the bit from spinning on the shaft of a round drive is a cross bolt. A hex drive functions like an Allen head wrench stuck in a socket head screw, so it’s the hex that is making the drive — not the cross bolt. The cross bolt is there just to hold the bit onto the shaft, as opposed to transferring torque.”

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Know Your Needs
When it comes down to it, choosing the right auger attachment is no different than picking out any other tool for your business. “Determine what areas you are going to be using the auger attachment — your possible environments and surroundings,” suggests Amerman. “Today, you might need a standard-duty bit, but down the road you might need more torque, more speed or a completely different style of bit. So, just knowing your potential uses and ground conditions can really pay off.”

And just as with any work tool, the most important part is matching the auger attachment to the intended carrier machine and to the job conditions. Manufacturers cannot stress enough the importance of matching the hydraulic flow of your auger attachment with the intended tool carrier. On the outside, many auger drives are essentially identical. And it doesn’t matter whether you want to use a skid steer, backhoe loader, excavator, compact track loader or tractor — the volume of the motor must match up with the available flow of the machine.

Auger attachments are grouped by flow range to correspond to the appropriate carrier — from 15 up to 35 or 40 gallons per minute (gpm). According to manufacturers, operators should never try to get more out of a 10-gpm power head, for example, by hooking it up to a skid steer that produces a 35-gpm flow. While this might be an exaggerated hypothetical, it does demonstrate the importance of knowing your equipment, your application and your environment.
“In certain instances, customers are going to need high torque and low speed — especially if they are going to have a large auger in very hard digging applications,” says Jones. “But if you are looking at smaller diameter holes in easy-digging dirt, then speed becomes a more valuable tool than torque. Overall, the best advice you can give a customer is to get the right tool for the job. If a guy is only going to dig five postholes, then he really doesn’t need to buy anything too heavy-duty.”

Nick Zubko is associate editor of Compact Equipment.

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