Choosing the Right Bit for Your Billy Goat AGR1300H Auger

Billy Goat AGR1300H Auger partsThe new Billy Goat AGR1300H’s Z-Link drill mount makes it one of the easiest-to-use augers on the market at any price. This machine can handle 2-18 inch bits and works with 7/8 inch square, 1 ¼ inch square and 1 3/8 inch hex bits with the right adapter. With so many options, that leaves one question: which bit do you need to use? Here’s how you can break down your choice based on why and where you’re drilling.

How an Auger Works

An auger is made of four parts, with each one contributing to performance:

– The pilot bit creates a small hole to help line up the rest of the auger bit.
– The teeth shave off layers of soil, creating the hole.
– The flighting that wraps around the shaft lifts the dirt out of the hole.
– The top of the shaft has a hole that fits over the head of the auger’s drive system.

Auger Bit Types and Sizing

There are two ways to measure a bit’s width: strip width and total width. The strip width is the width of the flighting from the shaft to the outer edge. The outer diameter is the total width of the auger bit. This includes the shaft width and two times the strip width, once for each side of the bit.

The helix direction is the direction the flighting wraps around the bit. Think of it in terms of a bolt. If you need to turn the bit clockwise to screw it in, the bit has a right-hand helix. Most bits are right-hand, so spinning the bit clockwise cuts into the soil. If the bit needs to spin counter-clockwise, it’s a left-hand helix.

A 7/8 inch square bit adapter comes with the AGR1300H from the factory. It can be swapped out with a 1 3/8 hex adapter or a 1 ¼ inch square adapter to fit matching bits.

Choosing the Right Bit for Digging Post Holes

As a general rule of thumb, a post should be at least 1/3 as deep in the ground as its total height above the ground. For example, if you’re building a 6-foot high fence, each post hole needs to be at least two feet deep. Gate posts need to be deeper to handle the twisting forces of the gate. Height will vary depending on the gate design, but up to 50% is typical. If you live in an area that gets cold enough for the ground to freeze, the post needs to be below the frost line. Otherwise, frost heaving will gradually push the post out of the ground.

The hole width should be three times the post width. This lets you place the post in the ground and compact soil around it. Once you fill the hole, don’t be surprised if the post isn’t firm. It will take a while for the ground to settle and hold the post in place fully, even if you anchored it with concrete.

Choosing Bits for Other Uses

The AGR1300H can do more than just drill post holes. Here’s how you can match the right bit width to the job at hand.

2 inches wide: Boring under sidewalks, planting grass plugs, installing termite bait traps, soil moisture probes and stakes for trees
3 inches wide: Installing sand and snow fences. Mixing seeds, fertilizer, and other soil additions
4 to 5 inches wide: Planting three-inch potted plants, quart-size potted plants, shrubs, and large bulbs
7 to 9 inches wide: Planting one to two-gallon potted plants

In some situations, like boring under sidewalks, you may need to drill at an angle. This isn’t a problem for Billy Goat’s auger, but it does decreases efficiency. At 90 degrees, the bit will only drill 35-40% as fast as it would when drilling straight down.

Choosing the Right Pilot Bits and Teeth

The teeth and pilot bit do the cutting, so they wear out long before the flighting. That’s why these parts are made to be removable. Choosing the right material depends on the soil you’re working with.

Carbide is the hardest, most brittle material. It has no trouble breaking through rocks, but it also wears out the fastest.

Dirt bits and teeth use soft metal that is hard-wearing, but they blunt easily when striking rocks.

Hardface bits and teeth have hardened surfaces with a soft core. This balances the wear of dirt bits with the cutting ability of carbide bits.

We Have the OEM Billy Goat Parts and Accessories You Need

Do you need to get a new bit for your auger? Want an adapter to use 1 ¼ inch square or 1 3/8 inch hex bits with your AGR1300H? Billy Goat Parts has all that and more. We’re a certified Billy Goat and Honda dealer, which means we carry accessories for your machine as well as factory parts. Visit us at We ship across the United States and Canada.

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