Tool Test: Wood-Boring Bits
The best bits pull through the material without too much effort and leave a clean hole in their wake.
Synopsis: In this tool test, we put twelve 1/2-in. and 3/4-in. bits to the text, drilling through framing lumber and PT 4x4s, as well as intentionally striking a nail to see how the bit reacts to the damage and performs afterward. Some standout bits leave particularly clean holes or chew through nails with ease, and we identify a best value bit as well as a best overall performer.
F or nearly everyone who works in residential construction, wood-boring bits are the preferred way to make medium-sized holes. They’re easy to find in stores, they’re not too expensive, and they generally last a long time even with almost everyday use. During framing, wood-boring bits are used to drill sill plates for anchor bolts, and sometimes to recess their washers and nuts. You’ll see them used during the mechanical rough-in phase when they’re used for most of the drilling through framing for electrical wires and small-diameter pipes. Toward the finish stage, wood-boring bits are used for things like drilling cabinets for pipes and wires, and for drilling mounting blocks and siding for exterior lights and outdoor receptacles .
The wood-boring bits in this test are meant for fast drilling, and as a consequence, many leave a ragged, splintery hole. If you’re looking for a nice, clean hole presentable for finished work, you’ll probably want to use a Forstner bit. On the occasion that you need to drill a hole for larger pipes or ductwork, you’ll need to use a hole saw, because wood-boring bits like the ones I tested max out at around 1-1⁄4 in. to 1-1⁄2 in. in diameter.
How we tested
To test the bits, I laid all the material flat on sawhorses at standard working height. After drilling all the 1⁄2-in. and 3⁄4-in. holes of the same bit brand and type, I installed a fresh battery on the drill to judge the next pair of bits. The test process was as follows:
1. Drill eight holes in 2×6 framing lumber. This simulates drilling into a stud, joist, or plate.
2. Drill three holes in a pressure-treated 4×4. This simulates drilling into a deck post, perhaps for hardware such as a carriage bolt.
3. Intentionally nail-strike a 3-in. framing nail embedded in the 2×4. This simulates an unintentional nail strike while drilling near a connecting point in framing material.
4. Return to the original 2×6 and drill two holes. This judges how the newly damaged drill bit performs in the original work.
Spade bits vs. auger bits
Wood-boring bits can be grouped into two main categories: spade and auger. Historically, spade and auger bits were considered commodity-type consumables. Modern versions are notably more complex in shape, and sometimes combine aspects of both spade- and auger-bit geometry. The manufacturers claim that the hybrid shapes are “fastest” or “cleanest,” or that they make drilling “effortless,” which is not always the case. Hybrid features include auger tips, sharpened curved flutes, coated flutes, and curved paddles.
Sometimes called paddle bits, spade bits are the least expensive of the group. These bits have a pointed or auger tip, followed by sharp, pronounced shoulders that do the cutting. Spade bits are widely available at nearly all box stores, hardware stores, and lumberyards. They can be purchased individually or in larger sets, ranging in size from 1⁄4 in. to 1-1⁄2 in., often in 1⁄16-in. increments. All of these bits are impact-ready and have a 1⁄4-in. hex shaft. Standard spade bits are usually 6 in. long, but you can get stubby versions that are 4 in. and “installer” versions commonly available in 12-in. and 16-in. lengths.
In comparison, auger bits generally look like traditional twist bits, but larger in diameter. The flutes that wind in a spiral make these bits better at chip extraction. Auger bits, sometimes called “ship augers,” usually have two flutes along the shaft of the bit, but sometimes one or three flutes. Auger bits are available in sizes similar to spade bits and have several sizes of shafts for securing in a drill chuck. These bits are also more expensive than spade bits. Manufacturers don’t always use the word “auger” to describe these bits. Instead, popular brands use terms such as self-feeding bits, power bits, tri-flute bits, or utility bits.
Put to the test
For testing the bits, we chose the two most commonly used bit sizes: 1⁄2 in. and 3⁄4 in. Half-inch holes are common for running nonmetallic electric cable, while 3⁄4-in. holes are frequently used for running 1⁄2-in. PEX and copper tubing for domestic water lines. I used an 18v cordless drill with a keyless chuck for testing, because that’s what I see plumbers and electricians using for drilling holes this size. Right-angle and other large drills are generally reserved for holes 1-1⁄2 in. and up.
All testing with the drill/driver was done on the “low” setting. This translates to higher torque, but lower rpm. This levels the playing field, as some bits are not meant to spin faster than 600 rpm, and the highest possible rpm on the “low” setting is 400. A standard 1⁄2-in. keyless chuck in a cordless drill allowed me to use of all of the bits, as some bits have larger shanks than others. A 1⁄4-in. hex head on an impact driver couldn’t accommodate some of the larger bits.
I drilled holes in 2×6 SPF framing lumber, 4×4 pressure-treated post material, and nail-embedded 2×4 SPF framing lumber. I judged the speed of drilling, the effort required, and hole cleanliness. I also intentionally ran the bits into nails and judged their performance afterward.
What makes a winner?
Of the spade bits, there was no clear standout that performed better than others. Nearly all of the spade bits achieved the same results in the same manner. The Spyder Stinger spade bits pulled notably well through the testing material, but still only marginally better than the rest of the group. For boring holes in wood, spade bits will suit the majority of your needs just fine, especially given their availability and price point. They have no problem drilling through pressure-treated 4x material and generally leave clean holes.
The results of the auger bit testing were more interesting than their spade bit competitors. Auger bits are better for drilling through big timbers and built-up beams, as they pull through the material more easily than their spade bit counterparts. If your work makes it likely you’ll strike a nail on occasion, you’ll be pleased to know most bits came through my intentional strikes largely unscathed and were able to drill new holes after hitting a nail. Some auger bits made a clean entry but drilled slowly. Others drilled quickly, but left a messy hole, while one (the Milwaukee Speed Feed auger bit) couldn’t drill through the material at all due to the tip getting clogged.
Some of the 3⁄4-in. auger bit holes were tough to keep clean inside the lumber. The cutting edges on the bits really dig into the material, shearing the wood in larger chunks, but not pushing material out of the hole in the same way that a spade bit does.
Do clean holes really matter? I think it depends. For ledger bolts and other bolted connections, it probably doesn’t matter, but I think a strong argument can be made that a cleaner hole will make it easier to run wires and piping through them. Additionally, a clean hole means less likelihood of damaging a cable as it’s pulled. One thing that surprised me is that the 3⁄4-in. spade bits had a tough time striking through the embedded nail. On the other hand, the 1⁄2-in. bits were able to either go through or wiggle around the nail. So if you think you might hit a nail or screw, use a smaller-diameter bit if you can.
Jeremy Kassel ( @kasselconstruction ) owns Kassel Construction in Glenmont, N.Y. Photos by Rodney Diaz, except where noted.
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From Fine Homebuilding #314