Drill & Boring Bits Explained: Twist, Brad-Point, Spade, Forstner, Auger & More

Open a drawer of old bits at an estate sale — twist bits gone rusty, a flat spade paddle, something with a wicked screw tip, one wide flat-bottomed cutter that looks almost architectural — and the question is always the same: what is this thing, and what was it made to cut? Boring bits are among the most misidentified tools in a shop, because so many of them solve the same problem, a round hole in wood, by entirely different means.

At Viridian Eclection, we carry real, working antique and vintage tools alongside our furniture and decorative pieces, and the hand brace with its bits is one of the most asked-about groups in the shop. This guide covers every major boring bit — twist, brad-point, spade, Forstner, auger, plus the countersinks, counterbores, hole saws, and plug cutters that finish the job — so you can identify what is in your own drawer and use it correctly.

The Everyday Bits: Twist and Brad-Point

Twist (Jobber) Bits

The twist bit, or jobber bit, is the one everyone recognizes: a fluted, spiral shaft ending in an angled cutting point, made for wood, metal, and plastic alike. It is a generalist. In metal, that point centers itself reasonably well; in wood, it has no true guide, so it can wander or skate before it catches, especially on curved or end-grain surfaces. Reach for a twist bit when exact placement matters less than simply getting a hole there.

Brad-Point Bits

A brad-point bit solves the twist bit's wandering problem. Its tip shows a sharp center spur flanked by two raised side spurs: the center point locates the hole exactly where you set it, pressed into an awl-marked center, while the side spurs score the wood cleanly before the flutes clear the waste. The result is a precisely located, tear-free hole — the standard for doweling, hinge boring, and joinery that has to land exactly on the mark.

The Wide Cutters: Spade and Forstner Bits

This is where most of the confusion begins: two very different bits share the same basic idea — a wide cutting edge around a center point — and both turn up in almost any old tool chest.

Spade (Paddle) Bits

A spade bit, also called a paddle bit, is exactly what it looks like: a flat, wide steel blade with a sharp center point and two flat cutting wings that shave wood as the bit spins. There is no rim, no circular scoring edge — just that flat paddle shape, which is why it reads as almost razor-like. It is built for speed, clearing a wide hole fast at the cost of a rougher wall and a tendency to blow out the far side as the point breaks through — the right bit for rough carpentry and wiring holes.

Forstner Bits

A Forstner bit is built around that same wide, center-pointed idea but solves it differently. It has a short center spur for location and a sharp circular rim that scores a complete ring before flat interior cutters clean out the waste inside it. Because the rim — not the point — does the guiding, a Forstner bit produces a smooth-sided, genuinely flat-bottomed hole, with far less tear-out than a spade bit leaves behind. That rim guidance also lets it do what no spade or twist bit can: bore a hole that only partly overlaps an existing one, bore at a steep angle without skating, or cut flat-bottomed mortises and hardware recesses. The trade-off is speed.

Solving the Mystery: Which Bit Is Yours?

If you are picturing a wide, razor-edged cutter that bores something close to a half-inch hole around a center point, you are almost certainly picturing one of these two — and the tell is the shape of the edge. A single flat blade with two angled wings, and nothing that looks like a rim, is a spade bit. A short spur at the center surrounded by a distinct circular rim or toothed ring is a Forstner bit. Set the bit flat on a table: a spade bit rocks on its blade, while a Forstner bit sits flush on its rim — flat blade versus circular rim explains everything else about how each one cuts.

The Auger Bit: Deep Holes and a Brace to Turn Them

How an Auger Bit Works

An auger bit is built for depth. Its most recognizable feature is a threaded, screw-shaped lead point at the tip — a true self-feed mechanism, pulling the bit into the wood under its own thread rather than relying on hand pressure the way a twist or spade bit does. Behind it sit spurs that score the hole's rim, followed by wide cutting lips and a long spiral shaft that carries waste out of a deep hole — a clean, straight bore in thick stock, exactly what's needed for wiring runs through joists or deep mortises. Because the lead screw pulls on its own, an auger bit should never be run at high speed in a power drill: it can grab and pull through faster than expected, jolting tool and wood alike. Auger bits are made to be turned slowly and deliberately.

The Hand Brace — An Antique Tool Still at Work

That traditional partner is the hand brace: a U-shaped steel frame with a chuck at one end, a knob at the other, and a swept crank handle between them that lets a woodworker apply slow, steady, high-torque rotation by hand. Russell Jennings Manufacturing Company of Deep River, Connecticut, patented its extension-lip auger bit design in 1855 and remained the trade's benchmark for decades, prized for its extended spurs and finely threaded lead screw; Irwin, its longtime competitor, introduced a pivoting-drawer bit box in 1892. A ratcheting brace that still turns smoothly, holding a matched set of period auger bits, is a genuinely usable antique — not a display piece.

Countersinks, Counterbores, Hole Saws & Plug Cutters

Countersink vs. Counterbore

These two are frequently confused. A countersink cuts a short, cone-shaped recess matching the underside of a flathead screw, so its head sits flush with the surface. A counterbore is different: a wider, flat-bottomed cylindrical recess sized to sink a screw head below the surface, leaving room for a wooden plug. A countersink makes a screw disappear at the surface; a counterbore buries it and hides the evidence.

Hole Saws and Plug Cutters

A hole saw is a toothed steel cylinder on an arbor with a small pilot bit at its center — the pilot locates the cut while the ring of teeth removes only the perimeter of a large hole, rather than boring solid material the way a Forstner bit does. It is the tool for door-lock installations and any hole too large for a standard boring bit. A plug cutter works the opposite way, cutting small cylindrical plugs from scrap to conceal a screw in a counterbored hole — the traditional finishing move for fine furniture repair.

Tips for Clean, Accurate Holes

Whichever bit is in your hand, a few habits separate a clean hole from a ruined workpiece:

• Mark your center with an awl. A small punched dimple gives any center point somewhere exact to seat.
• Reach for brad-point or Forstner when placement matters. A true center point outperforms a plain twist bit.
• Back the work with scrap. Sacrificial wood behind the workpiece prevents blow-out on breakthrough.
• Match speed to bit size. Large bits — spade, Forstner, hole saw — want slow rotation; small twist bits can run faster.
• Let the bit clear its own chips. Backing an auger or Forstner bit out periodically keeps the flutes from packing.
• Clamp the work. A hand-held board can spin the moment a bit catches.

Vintage Bits Worth Collecting — and How to Care for Them

Named Makers to Know

Boring bits are one of the few tool categories where the maker's name is stamped directly onto the working steel, satisfying to research and date. Beyond Russell Jennings and Irwin auger bits, look for the name Forstner itself — the bit takes its name from Benjamin Forstner, a gunsmith and inventor in Salem, Oregon, who patented the design in 1886. His innovation was really a subtraction: he eliminated the lead screw and cutting lips every earlier boring bit relied on, guiding the cut instead with that now-familiar rim. A complete boxed set of period auger bits, or an early Forstner-pattern bit still stamped and legible, is a genuine piece of tool history.

Sharpening and Caring for Old Bits

A vintage bit that has lost its edge is not necessarily lost. Light surface rust generally responds well to fine steel wool and oil rather than aggressive abrasives that erase original markings and value — our guide to restoring antique tools without destroying their value covers the gentler methods we use in the shop. For the edges, a light touch-up with a fine slip stone, following the bit's original bevel, restores a working edge without erasing its history. The goal is always the same: keep it usable, not make it new.

At a Glance

• Twist bits are generalists for wood and metal but have no center point, so they can wander in wood.
• Brad-point bits add a center spur and two side spurs for clean, precisely located holes with no wander.
• Spade bits are a flat, wide blade with a center point — fast, but rougher-edged holes.
• Forstner bits use a center spur plus a circular scoring rim — slower, but clean, flat-bottomed, and able to bore partial, angled, or overlapping holes.
• Auger bits self-feed on a threaded lead screw for deep, clean holes — the classic bit for a hand brace, never run fast in a power drill.
• Countersinks seat a screw head flush; counterbores sink it below the surface, often under a wooden plug.

Frequently Asked Questions

I have a wide, razor-edged bit that cuts about a half-inch hole around a center point — what is it?

Almost certainly a spade bit or a Forstner bit. Lay it flat: a single flat paddle with two angled wings that rocks when set down is a spade bit. A short center spur surrounded by a distinct circular rim that sits flush is a Forstner bit. The spade cuts faster and rougher; the Forstner cuts slower and leaves a clean, flat-bottomed hole.

Can I use an antique auger bit in a modern power drill?

Yes, but run it slowly. The threaded lead screw self-feeds into the wood, and at high speed that same action can grab and pull the bit through faster than expected. Auger bits were designed for the slow, high-torque turning of a hand brace, so a power drill should run at low speed with a firm two-handed grip.

How do I keep an antique brace and its bits usable, not just decorative?

Keep surface rust in check with fine steel wool and a light oil rather than harsh abrasives, and touch up a dulled edge with a fine slip stone following the bit's existing bevel. A period Russell Jennings or Irwin bit, kept lightly oiled and sharp, still bores as cleanly today as it did a century ago.

Conclusion

Every one of these bits solves the same problem — a round hole in wood — in a slightly different way: a wandering point, a rough edge, a hole too deep to reach, a screw that needs to vanish beneath the surface. Learning to read a bit's cutting edge is learning that history: the lead screw on an auger, the rim on a Forstner, the flat blade on a spade. A drawer of old bits stops being a mystery once you know what each one was built to do — and a well-made vintage set, brace and all, is still entirely capable of doing it.

Explore our curated collection of antique and vintage tools at The Eclection, or read further in our guide to identifying collectible antique woodworking tools.

Resources & Further Reading

For deeper study, these museums and collector organizations are reliable, non-commercial starting points:

• Smithsonian National Museum of American History — American tools, trades, and industry.
• Early American Industries Association — preserving the history of early tools and trades.
• Mid-West Tool Collectors Association — a leading antique-tool collectors' organization.