With prices ranging from about$35 up to $280, you’re probablyasking yourself why you should

buy a four-jaw chuck for your lathe. Hereare some of the best reasons:� Chucks provide quick, accurate, and pos-itive centering of bowl blanks and standardturning squares.� There’s no need to glue a waste block toyour turning blank or give up bowl-blankthickness to accommodate the screws need-ed to fasten it to a faceplate.

� When using a chuck to turn a bowl fromgreen stock, you can rough it out, remove itfrom the lathe, and then later remount itwith greater ease and convenience thanwith faceplate mounting.� Accessory chuck jaws are available tohold work as small as a ‹"-diameter tenonon a miniature vessel and as large as the rimof an 18"-diameter platter.� You can turn a bowl and finish it insideand out with little or no trace of how it washeld on the lathe.

84 DS-061a WOOD magazine June/July 2004

getting a grip on

Teknatool of New Zealand started the woodturning chuck revolution in 1988. Shown above is the business end of its Nova Titan chuck.

When first introduced, four-

jaw chucks were viewed by

many as a luxury just for

professional turners. But

they offer so many advan-

tages that anyone from

novice level on up would

benefit from owning one.

four-jaw lathe chucks

How a chuck worksA chuck consists of a body, jaw slides, andjaws, as shown above. Internal spiral gear-ing moves all four jaws simultaneously,keeping them equidistant from the center ofthe chuck body. The jaws operate with twinlevers or a single key. Lever action requireseither the simultaneous use of both hands,or temporarily locking the lathe spindle toadjust the chuck with one lever. Single-keychucks offer the advantage of one-handoperation without the necessity of lockingthe lathe spindle. One-hand tightening orloosening leaves the other hand free to con-trol stock when mounting it or a finishedpiece when removing it from the chuck.

Jaw designThere are two basic jaw designs, dovetailand serrated, as shown below. Most jawsfor Vicmarc and Axminster chucks are ofthe dovetail design. The flanged SuperNovajaws are a variation of this design. Serratedjaws are most common on Oneway chucks.

How a chuck gripsChuck jaws either contract around a turnedspigot (round tenon) or expand into a hol-lowed-out recess. In contracting mode, thejaws commonly supplied with chucks gripspigots from 1fi" to 3" in diameter. Thesesame jaws expand into turned recesses from2" to 3fi" in diameter.

Because chuck jaws form a circle whencompletely closed, they make continuouscontact when contracting around a spigot orexpanding into a recess that is just slightlylarger than the diameter of the circle, asshown above. This provides the greatest

85woodmagazine.com

Bowl withdovetail recess

Dovetailspigot Bowl with

d ilBowl with

dovetail recessBowl with

dovetail recessDovetailspigot

The chuck jaws attach to the jaw slides withmachine screws, allowing the use of a widevariety of specialized accessory jaws.

Dovetail jaws usually leave minimal or no marking on the finished ves-sel, reducing the need to remount it to remove any marks.

holding power and safest operation. As thejaws approach their maximum open posi-tion they make only point contact with theworkpiece, as shown above. Gripping onlyat these points (eight in contracting mode,or four in expanding mode) is less secureand risks marring the wood. Manufacturersoffer accessory jaws to cover a wide rangeof gripping diameters.

When turning, be careful of chuck jawsadjusted near their maximum diameter. Thefarther open the jaws, the more they extendbeyond the chuck body, and if touched, themore likely they are to cause injury.

Serrated jaws have great holding power, particularly when grip-ping end-grain stock, but leave marks that must be removed.

Machine screw

Body

Jaw slide

Hex wrench

Jaw

Expanding into a recess

Expanding into a recess

(Chuck viewed straight on looking toward the headstock)

Contractingaround a spigot

Contractingaround a spigot

KEY CHUCK PARTS

TWO JAW TYPES GIVE YOU DIFFERENT ADVANTAGES

HOW FAR YOU OPEN A CHUCK AFFECTS ITS GRIPPING POWER

Dovetail

jaw

Serrated

jaw

Two jaws

removed

for clarity

Two jaws

removed

for clarity

Jaw motion Workpiece point of contact

JAWS NEAR MINIMUM OPENINGPROVIDE MAXIMUM GRIP

JAWS NEAR MAXIMUM OPENINGPROVIDE LESS GRIP

Dovetail jaws contracting around a spigot: When forming aspigot at the bottom of a bowl, match the angle of the outsideedge of the spigot to the angle of the jaws.

the screw. Engage the lathe tail center foradditional support while turning the roughshape of the bowl. Now turn the outside ofthe bowl, shaping its bottom to be held bythe chuck jaws, as shown in the photo atleft. Screw-center mounting allows for easyremoval and remounting of the blank whilemaintaining its centered position.

Shape the bottomWhen shaping the outside of a bowl, formits bottom to fit your chuck jaws so you canreverse the blank, grip it with the chuck,and form the inside. For contracting dove-tail jaws, form a dovetail spigot as shownbelow left. Cut the inside corner where thespigot meets the bowl body crisp and cleanto provide a positive gripping corner for thechuck jaws. Leave a flat bearing surface forthe jaw ends. Because the jaws pull in onthe spigot as well as squeezing it, make thespigot slightly shorter than the jaw depth, soit does not bottom out. Sand and finish asmuch of the outside of the bowl as possible.

The same jaws that contract onto a spigotalso will expand into a recess hollowed outin the bottom of a bowl, as shown below.When planning the shape of your bowl,leave extra thickness in its bottom toaccommodate this recess. Make it about¤–‹" deep, cleanly cut, and with its edgefollowing the shape of thejaws. Leave sufficient

Start on the outsideFor mounting side-grain bowl blanks, manychucks come with a screw center. To usethis center, install it in the chuck by grip-

ping it with the jaws. Drill a hole equal indiameter to the root of the screw and slight-ly deeper than its length, centered on the topface of the blank. Then thread the blank onto

86 WOOD magazine June/July 2004

With its exterior shaped, this partially formed bowl was cut in half to show how the screwcenter secures it to the chuck.

Turning a bowl with a four-jaw chuck

Dovetail jaws expanding into a recess: When form-ing a recess in the bottom of a bowl, match the angle of the inside rim of the recess to the angle of the jaws.

FIRST, MOUNT THE BLANK ON A SCREW CENTER, AND SHAPE THE OUTSIDE

Tail center

Two chuck jaws

removed for clarity

Screw center

Jaw

Dovetail spigot

Flat bearing surface

Dovetail

recess

THEN, GRIP THE BOWL BOTTOM IN ONE OF TWO WAYS, AND FORM THE INSIDE

Two chuck jaws

removed for clarityTwo chuck jaws

removed for clarity

87woodmagazine.com

wood around the recess to sup-port the outward force exerted bythe expanding jaws. Gripping thebowl in this manner allows youto completely form the outside,including its bottom. With theoutside of the bowl formed, sandit and apply a finish.

Generally speaking, contract-ing onto a spigot providesthe greatest holding power.However, for turnings of largediameter but shallow depth, suchas a large platter, expanding intoa recess gives better results.Regardless of how the chuckholds the workpiece, be sure toperiodically check its tightness.

Now form the insideWith the outside of the bowlcomplete, remove it from thescrew center, and remove thescrew center from the chuck. Tohollow the inside of the bowl, remount it asshown, opposite page, bottom. When turn-ing the inside, take care not to catch thetool. Chucks do not hold turning stock assecurely as a standard faceplate where sev-eral screws secure the blank. A bad catchcan dislodge the bowl from the chuck. Oncethe final inside shape and wall thickness ofthe bowl have been achieved, sand it andapply the finish. For a bowl gripped in arecess, simply remove it from the chuck.

Back to the bottomFor a bowl gripped by a spigot, reverse-chuck it, gripping the rim with a shop-madejam chuck or accessory adjustable bowljaws, as shown above. Then turn away thespigot, and form a slight recess in the bot-tom of the bowl. Whether using a jamchuck or a four-jaw chuck fitted with bowljaws, support the workpiece with the tailcenter for as long as possible. Finish-sandthe turned area, and apply a finish. ¿

This article wasproduced with thehelp of KipChristensen andRex Burningham.Kip teaches furniture designand prototyping at Brigham YoungUniversity inProvo, Utah. Hefrequently demon-strates turningtechniques atnational symposiaand workshops.Rex teaches turning at Craft Supplies USA, also inProvo. He exhibits his work in galleriesand craft shows, and has assisted suchlegendary turners as Richard Raffin,Rude Osolnik, Dale Nish, and Ray Key.

Kip Christensen

Rex Burningham

Although each manufacturer has a different name for this chuck accessory, adjustable bowl jaws allwork the same. Resilient grippers hold the bowl rim to the chuck jaws. Sets cost from $50 to $140.

Chucks also can gripmost common sizes ofturning squares.Because square stockcannot be held assecurely as roundstock, hold it with thechuck and support itwith a tail center, asshown at right. Thenturn a round spigot onthe tailstock end. Nowflip the square end forend, and grip the spigotin the chuck, onceagain supporting it withthe tail center. Whenyou cut square stockfor mounting in achuck, make accuracya priority; out-of-square stock is difficult to grip securely. The slightly roundedjaw corners of Oneway chucks offer the best design for gripping square stock.

Illustrations: Roxanne LeMoine

Meet the authors

BOWL JAWS MAKE IT EASY TO REMOVE A SPIGOT

One

jaw

Resilient

gripper

Tail center

Christe

nsen/B

urn

ing

ham

SourcesWoodturning chucks.

Packard Woodworks. Call 800/683-8876, or go topackardwoodworks.com.

Grizzly Industrial. Call 800/523-4777, or go to grizzly.com.

Penn State Industries. Call 800/377-7297, or go topennstateind.com.

Craft Supplies, USA. Call 800/551-8876, or go to wood-turnerscatalog.com.

Coming in issue 159. See Wise Buys in thisupcoming issue for reviews of four chucks priced fromabout $35 to $235.

A chuck also grips square stock

©Copyright Meredith Corporation 2004