Table of Contents
The packaging all looks the same, but the bits inside are engineered for completely different jobs. A brad point bit bores clean holes in oak, a twist bit does the same job in steel, a Forstner bit excavates a flat-bottomed pocket, and an auger bit chews through a 2x4 in seconds. Choosing the wrong family gives you blown-out exits, burnt edges, wandering points, and bits that snap in the chuck.
Each bit’s shape solves a specific problem: keeping a hole on center, cutting a flat bottom, clearing chips, or surviving contact with metal. Name the problem, and choosing a bit takes seconds.
Start With the Hole, Not the Bit
Before reaching for a bit, describe the hole you need. Diameter and depth are obvious, but four other properties decide the family. Entry quality matters when the hole shows on a finished surface. Exit quality matters when the bit breaks through into a show face. Bottom geometry matters when a hinge, magnet, or plug must sit flat. Chip clearance matters when the hole runs deeper than three times its diameter.
Material decides the rest. Wood cuts cleanly at high surface speeds. Steel and aluminum need slower speeds, sharper edges, and flutes that manage stringy chips and heat. Masonry needs a hammering action that pulverizes rather than slices. No single bit does all three well.
Brad Point Bits: Clean Entry in Wood
A brad point bit, sometimes called a dowel bit, starts with a sharp center spur that pulls the bit straight into the wood instead of skating across the surface. Two raised spurs at the outside diameter score the circumference before the flutes lift chips, leaving a crisp rim with no torn fibers — exactly what visible joinery needs.
Brad points excel at dowel holes, shelf-pin holes, hinge pilots, and any operation where the surface shows. Sizes from 1/8 inch to 1/2 inch cover most furniture work. Run them at moderate speed with steady pressure and clear the flutes often. On through-holes, clamp a backing board behind the work to prevent blowout at the exit.
A brad point will not survive steel, and it dulls quickly on hardboard, so reserve a set for wood.
Twist Bits: The Multi-Material Standard
The twist bit is the generalist of the drawer. Spiral flutes clear chips, and the point comes in two common geometries. A 118-degree point is the traditional all-purpose grind and tends to skate on smooth metal until a center punch gives it a start. A 135-degree split point cuts at the tip, which reduces walking and makes the bit far friendlier in a hand drill.
Twist bits come in high-speed steel for general use and cobalt for harder metals and higher heat. Jobber length is standard; mechanics length is shorter and stiffer for tight spaces. In wood, a twist bit falls between a brad point and a spade bit — usable, but it tends to tear the entry rim and wander off center without a pilot.
Use twist bits for pilot holes, for drilling through mixed materials like a steel bracket into a stud, and for anything metal. Keep a dedicated set for metal and a beater set for wood and drywall; once a bit has drilled abrasive material, it will never cut steel cleanly again.
Forstner Bits: Flat Bottoms and Clean Rims
A Forstner bit cuts with a circular rim that severs the fibers around the hole, then a pair of cutting lips removes the interior. The result is a flat-bottomed hole with a clean edge, and the bit can bore overlapping holes, angled holes, and holes that stop at an exact depth. That makes it the standard for hinge recesses, magnet pockets, dowel plugs, and waste removal in mortises.
Modern versions come with a small center point or a sawtooth rim. Sawtooth designs start more easily on smooth stock; pointed versions track better on curved or angled surfaces. Because the rim does the cutting, Forstner bits demand low speeds — usually 500 to 1000 rpm above 1 inch — and light, steady feed pressure. Clear chips every quarter inch in deep cuts, or the rim clogs and heat builds fast.
On a drill press with a fence and depth stop, a Forstner bit can bore a pocket to within a few thousandths of an inch, which is why cabinetmakers reach for one whenever inset hardware must sit flush. In a hand drill they are harder to control, so peck at the cut rather than leaning on it.
Auger Bits: Deep Boring With Control
Auger bits have a screw point that pulls the bit into the wood, deep flutes for aggressive chip clearance, and a spur that scores the rim. They are made for deep holes in framing lumber: running cable, boring door lock sets, and drilling angle holes for deck railings.
Traditional auger bits with tapered square shanks were made for a brace, and that combination remains one of the most controlled ways to bore a large hole by hand. The brace-and-bit approach to boring mortises still has real advantages in quiet shops and in work that demands low-speed control. Power auger bits with hex shanks cut fast enough that you must watch for breakthrough.
The screw point is the auger’s weakness as well as its strength. It will pull the bit through the work with almost no warning, so set a depth stop or wrap tape on the bit as a marker. It will also split thin stock, so back the work and slow down near the exit.
Spade Bits: Fast and Rough
A spade bit is a flat paddle with a point and two cutting spurs, and it exists to remove a lot of wood quickly. Sizes run from 1/4 inch to 1-1/2 inches, and hex-shanked versions drop straight into an impact driver or quick-change holder. In softwood, a sharp spade bit will bore a 1-inch hole through a 2x4 in a few seconds.
The tradeoff is finish quality. The entry rim tears, the hole walls are rough, and the exit usually blows out unless you back the work or drill halfway from each side. That is acceptable for framing, fencing, and utility work, not cabinet joinery. Spades also cut slightly oversized at high speed, so do not use them where hardware must fit closely.
Self-Feed Bits and Hole Saws
Self-feed bits look like a cross between an auger and a hole saw: a central screw pulls the bit in while a ring of cutters removes the circumference. Electricians and plumbers use them to bore large holes — often 1-1/2 to 4 inches — through studs and joists in one pass. The screw feed demands a powerful drill with a side handle, because the tool will twist if the bit binds.
Hole saws cover the same diameter range differently: a pilot bit sets the center, and a cylindrical saw with replaceable teeth cuts the rim. Bi-metal versions handle nails; carbide-grit versions cut tile and fiber cement. All struggle with wander and heat, and the fixes are the same: start with a pilot hole, run at low speed, and back off as soon as the teeth load up. Deep holes are a two-stage job, cutting from one side until the pilot breaks through, then finishing from the other side to avoid a blowout. For tracking and breakout control, see these methods for keeping hole saws from wandering.
Shanks: Round, Hex, SDS, and Quick-Change
The shank is the part that enters the chuck, and it determines which tool can hold the bit and how much runout you will get.
Round Shanks
Round shanks are the traditional standard and work in keyed and keyless chucks alike. The downside is slip: a smooth round shank in a worn chuck can spin under load, especially with larger bits.
Hex Shanks
A 1/4-inch hex shank locks into quick-change holders, impact drivers, and many modern drill chucks, and it will not slip. The format covers spade bits, pilot drills, countersinks, and driver bits. Do not assume a hex-shank bit is impact-rated unless the packaging says so.
SDS and SDS-Plus
SDS shanks have grooves that lock into rotary hammers and allow the bit to hammer and rotate independently. They are for masonry only; never put one in a standard three-jaw chuck.
Chuck and Holder Runout
Wobble is the enemy of accurate holes. A cheap keyless chuck, a bent bit, or debris in the jaws pushes a bit off center. Clean the jaws, seat the bit fully, and tighten every opening. Compact 12-volt drivers with tight chucks make accurate work easier in confined spaces, one reason these 12-volt drills for tight spaces see so much use in cabinet installs.
Pilot Holes, Countersinks, and Plug Cutters
Three small products solve most drilling problems around screws. A pilot hole prevents splitting and lets the screw pull the joint tight. As a rule, use the screw’s root diameter — the solid core between the threads — for hardwoods, and one size smaller than the shank for softwoods. A clearance hole through the top piece should match the shank diameter so the parts cinch together instead of jacking apart.
Countersinks cut the angled seat for a flat-head screw. A single-piece countersink with a pilot drill is convenient in softwoods; an adjustable cage is more flexible in hardwoods and prevents chattering. Plug cutters cut face-grain or end-grain plugs to hide countersunk screws; tapered cutters wedge tight, straight cutters make a cleaner cylinder. Cut plugs from the same board, orient the grain to match, then pare them flush. Pocket-hole work leans on the same principles with a dedicated bit and stop collar, and the pocket hole jig and drill pairing guide explains how step drills and collars work together. If you mostly build with pocket screws, this overview of drills for pocket hole joinery covers what to look for in the tool itself.
Speeds, Feeds, and Pressure by Material
Speed is where most hand-drilling problems start. A useful rule of thumb is rpm equals surface feet per minute times four, divided by the bit diameter in inches. Wood wants roughly 300 to 400 surface feet per minute, which puts a 1/4-inch bit near 5,000 rpm in theory and a 1-inch Forstner at 1,200 to 1,600. Cordless drills top out around 1,500 to 2,000 rpm, so most wood holes are happy at full trigger while large-diameter bits need the low gear.
Mild steel wants about 100 surface feet per minute and constant pressure to keep the edge cutting instead of rubbing. If the bit stops making a chip and starts squealing, you are work-hardening the metal and the bit will dull fast. Brushless drills hold speed under load better than brushed motors, which matters on hardwood and metal alike; the difference is covered in this comparison of brushless drills for hardwood.
Feed pressure should be firm and steady, not a hammer blow. Let the flutes clear chips; if the bit stops advancing, back it out and resume. For deep holes, peck in increments of one diameter. Heat is the enemy of every bit, and heat comes from spinning without cutting.
Preventing Tear-Out and Wander
Tear-out at the entry happens because the cutting edges lift fibers before they sever them. Put blue tape over the mark, or score the circumference with a knife before drilling, and the fibers stay put. Clamp a backer board behind through-holes, and drill from the show face whenever possible so any roughness ends up hidden.
Wander has three common causes: a smooth point on a smooth surface, an uneven surface like a knot or a curve, and too much speed with too little pressure. Fix it by center-punching, using a brad point or split-point bit, starting at low speed, and piloting anything larger than 3/8 inch. On angled or curved surfaces, drill a small pilot first, or set the bit in a V-block. Simple drilling guides and stop blocks are a natural shop jig project from scrap and pay for themselves the first time a shelf-pin hole lands where it belongs.
Sharpening and Caring for Bits
Every bit in the drawer cuts better and lasts longer with a little maintenance. Twist bits can be resharpened on a bench grinder with a light touch, or with a dedicated drill sharpener that indexes the point angle for you. Brad points are best touched up with a fine diamond paddle on the inside of the flutes and the two spurs, keeping the center point crisp. Forstner rims respond to a light diamond file. Spade bits are soft enough to file.
Rust is the other slow killer. Wipe bits with a light oil after use, keep them in a dry drawer, and never store them loose with other steel. If a bit has turned blue from heat or has a chipped cutting edge, it belongs in the scrap bin. The sharpening discipline that keeps chisels working applies here, and the range of sharpening stones available for edge tools is a useful reference if you want a maintenance station that covers bits as well as blades.
Frequently Asked Questions
Can I use brad point bits in metal? No. The center spur and scoring spurs are designed for wood and will dull or snap on steel, aluminum, or hardboard. Use a split-point twist bit for metal and keep the brad point set reserved for wood.
What is the difference between a Forstner bit and a spade bit? A Forstner bit cuts a clean, flat-bottomed hole with a smooth rim. A spade bit cuts a fast, rough hole with a torn rim and a blowout at the exit. Forstners are for joinery and hardware; spades are for framing and utility work.
Why does my drill bit wander on hardwood? Hardwood grain deflects a smooth point, especially at high speed. Center-punch or use a brad point, start at low rpm with firm pressure, and pilot anything larger than 3/8 inch. A drill guide or drill press removes the problem entirely.
Do I need a pilot hole for every screw? In hardwood, near board ends, and anywhere a screw sits within an inch of an edge, yes. In softwood and plywood, small screws often go in without one, but the joint pulls tighter and splits less when you drill a pilot.
How do I sharpen brad point and Forstner bits? Touch up brad points with a fine diamond paddle on the inside of the flutes and the spurs, keeping the center point sharp. Forstners respond to a light diamond file. Replace chipped or heat-blued bits.
What shank fits a standard cordless drill chuck? Round shanks and 1/4-inch hex shanks fit standard three-jaw chucks. Hex shanks also lock into quick-change holders and impact drivers. SDS shanks are for rotary hammers only and will not fit a standard chuck.