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M any years back, I hada commission to buildlockset displays. Thejob called for 18,000 holes withsmooth bores and crisp edgesin blocks of -in.-thick oak. Ata flat rate of 9 cents a hole, Icouldn't afford to let the wrong

drill bits slow me down.Before beginning, I experi-mented with a variety of meth-ods. I settled on Multispur bitschucked in a drill press. Theyproduced precise, tearout-freeholes and allowed me to workfast enough that I finished the

job in a little over a week. D epending on the project, otherlarge-hole boring tools mightbe worth considering. The most

common tools include Forstnerbits, spur bits, spade bits, holesaws and wing cutters.

Furniture, craft projects,architectural work and homerepairs often call for boringlarge holes. Large in my bookis anything more than in.dia., bigger than most com-monly ava ilable twist drill bits.Big holes demand special bits,and the variety on the marketincludes everything from in-expensive high-carbon-steelspade bits to costly Forstners.

Before spending a wad ofcash on a set of bits, considerhow often you need to drilllarge holes, the precision of cutrequired and how quickly youneed to get the job done.

For precision holes, picka Forstner or Multispur bitLike life forms, tools evolve

over time, only much faster.Forstners were developed morethan 100 years ago for use inhand braces. They were an im-provement over the other bitsof the time, such as brace bits,because Forstners could drilloverlapping and flat-bottomedholes. Forstners cut on twofronts: A sharp outer rim contin-uously scores the wood, anda pair of horizontal cutting

wedges removes most of the

Boring Big HolesWhen to use Forstners, Multispurs, spades,

hole saws and wing cutters

BY R O B E R T M. V A U G H A N

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waste inside the hole andshaves the bottom flat.

If brace bits were life forms,they'd be the fish of boringtools. Forstners are the amphib-ians. The 20th century sawyet another major evolution:Forstners emerged from the

swamp with teeth along theirrims. Although it would seemthat this would give the bit a big-ger bite, something more signif-icant happened. Like mammals,these sawtooth Forstners weremore efficient at heat regulation.Getting rid of the solid "rimmeant less metal-to-wood con-tact, which creates heat-produc-ing friction. With the adventof power tools, a cooler-run-ning bit was needed. Smooth-rimmed Forstners, especiallythose 1 in. and greater in diame-ter, tend to scorch wood whenused in an electric drill.

Today, we can choose amongtraditional Forstners, sawtoothForstners, Multispurs and spurbits. All do the same thing: Theydrill flat-bottomed holes withclean rims and smooth sides.(Although a traditional Multi-spur has only one cutting

wedge, the term multispurhasbecome synonymous with thesawtooth Forstner, which has apair of cutting wedges.) Thesebits are good for boring holesfor dowels or hardware, archi-tectural detailing or craft pro-jec ts, such as clock making,where you need a precise hole.

True Forstners have a stubbycenter point that just barely pro-trudes beyond the edge of the

rim. When centering the pointon a mark, you have to peekunder the bit to see if it's in theright place. Sawtooth Forstnersand Multispurs have slightlylonger center points, whichmake them easier to align.The se bits range from in. toas big as 4 in. dia., and pricesvary widely (see the box onp. 46). Spur bits have a pair ofcutting wedges and two small

spurs. They're made for boring

F O R S T N E R S A N D M U L T I S P U R S

at 90 to the surface. Many35mm bits for installing cup

hinges are of this style (see thetop right photo).

Because the outer rim of aForstner is smooth, it won'tcatch when drilling overlappingholes (see the bottom right pho-to) or when boring at an angle.Sawtooth Forstners and Multi-spurs can also be used to drilloverlapping holes, but be awarethat the teeth on these bitscan catch and hurl a workpiece

that isn't clamped down. When

drilling overlapping holes withthese bits, use a drill press and

firmly clamp the workpiece.

For fast drilling,use a spade bit

A spade bit is one of the sim-plest drill bits. It's nothing morethan a rod of steel with one endforged flat. The flat section isground away, leaving a sharppoint and a pair of cutting

wings. Spade bits are mostlyused in construction with

portable drills. These bits bore

Specialty spur bits.Spur bits

have a pair of small spurs ontheir rim, and they're made for

boring at90 to the surface. This

one is m ade for installing 35mmcup hinges.

Boring overlapping holes.

Forstner bits are good for rough-

ing out mortises.

holes quickly but tend to wob-ble and vibrate, causing a

raggedy rim on the entry sideand tearout and splintering onthe exit side. But when you'redrilling holes for wire or pipe instuds and joists, speed mattersmore than looks. For deepholes, withdraw the bit fre-quently to clear the chips, sothe bit won't bog down.When sharp and used at slow

speeds in a drill press, a spadebit can cut a fairly clean hole.

Spades are inexpensive and

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What's the difference between cheap bits and pricey bits?

The prices of Forstners, sawtooth Forstners and Multispur

bits vary widely depending on where you buy them, where

they're made and how long and thick their shanks are. I tried

four 2-in. bits from three continents, priced f rom $15 to $58,

and drilled a bunch of holes in hardwood (see the top photoon the facing page). Used in a drill press, all were capable of

boring holes with acceptably clean rims and fairly smooth

walls, although the cheapest bit cut the slowest.

So why the big price difference? The size of a bit's shank

plays some part: more steel means greater cost. Lower-cost

bits have -in. or -in. shanks about in. long. Higher-

priced bits have -in. or -in. shanks about 5 in. long. A

hefty shank provides additional stiffness, and the extra

length lets you bore deeper holes.

I ordered a $15 sawtooth Forstner bit, made in China, from

Woodcraft (800-225-1153), a retail chain and mail-order

company. This economy bit was slow-cutting. The rim of the

hole had som e minor tearout, but overall, it was acceptable.

The spurs and cutting wedge weren't ground as sharp as the

other bits. For occasional use, this bit would be a good value.A $3 5 Forstner bit from Austria, ordered through

Wood craft, came w ith a sharply ground outer rim. This

Forstner cuts faster than the Chinese bit, leaving a clean

hole. A $46 Multispur from Forest City Tool, made in

Hickory, N.C., cut faster tha n the other bits. The Multispur

produced some minor tearout at the edge of the hole and on

the wall. The most expensive bit, a $58 sawtooth Forstner

from Austria ordered from Woo dcraft, cut as fast as the

U.S.-made bit but left a tearout-free rim and a clean wall.

Anatole Burkin, associate editor

For speed, choose a

spadebit.Holes for

threading pipe or conduitin framing lumber don't

have to be pretty.

Spades are easy to

customize.Just file away

equal amounts on each side

of the blade to create a

narrower or tapered bit.

simply designed, which makesthem a good choice if you needto reshape one for a special job.If you need to drill a hole to ac-cept a 1-in. dowel that's sized ahair under 1 in., just file away anequal amount on both outside

wings of a 1-in. spade bit tomatch the dowel's diameter(see the bottom left photo), Or,if you want a slightly taperedhole, you can file a taper ontothe outside wings. Spade bitsrange from in. to in. dia.and cost about $2 apiece.

Hole saws are goodfor installing locksets

A hole saw, like a spade bit, haslimited use in furnituremaking,but it can be handy around the

house. Hole saws come in dif-ferent styles, but they generallyhave an arbor that holds both apilot twist drill (usually in.)and a larger cutting cylinder,

in. or larger (see the photo atright). More expensive holesaws come in kits with an arborthat accepts hardened steelcylinders of various sizes. Costsare based on the size of cylin-ders; for a good arbor and a 2-in.

bit, expect to pay about $20.

The cutting cylinder has fineteeth, like those found on ahacksaw. Inexpensive holesaws have thin-walled cylindersthat flex like a hacksaw blade,and these sometimes pop offthe arbor. They cost about $10.

Hole saws are commonly usedin portable drills by plumbersand electricians for boring pipeand conduit holes. They're goodfor drilling holes for locksets indoors. When using a hole saw,

Holesaws haveself-centering

pilot bits.They make quick work

of dr i l ling out do ors for locksets.

You can use them in a portable

drill or drill press.

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