tusk tenon table — synchronized simplicity · 2019. 4. 9. · synchronized simplicity harness the...

• Step by Step constructioninstruction.

• A complete bill of materials.

• Exploded view and elevationdrawings.

• How-to photos with instructivecaptions.

• Tips to help you complete theproject and become a betterwoodworker.

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WJ090

“America’s leading woodworking authority”™

Tusk Tenon Table —Synchronized Simplicity

Published in Woodworker’s Journal “Practical Woodworking:Proven Projects, Tips and Tricks from Fellow Woodworkers”

WOODWORKER'S JOURNAL ©2007 ALL RIGHTS RESERVED

Inside leg

Leg block

Foldingwedge

Foldingwedge

Mortiseblock

Leg block

Outside leg

Short shoulder rail

Stretcher rail

Shoulder rails

Rail extensionstrips

Folding Wedges Joint

138 HOME PROJECTS

Wedge—how big?What angle of slope?

Tusk tenon

“Pull-up” space aswedge is tightened.

How long?

Lines ofsheer stress

Shoulder thatresists the wedge

Traditional Tusk Tenon Joint

Parts and design considerations for making a traditional tusktenon joint with vertical wedge.


Elegant to the eye, this table’s joinery isbuilt up to create a knockdown capability.Folding wedges in built-up mortises arejust one of the factors that make it so.

TUSK TENON TABLE 139

Tusk Tenon Table —Synchronized SimplicityHarness the power of folding wedges by building this elegant tusk tenon table. You’ll

use ordinary thickness stock and joinery done by adding pieces rather than cutting

out material. Master woodworker Ian Kirby shows you everything you need to know.

A tusk tenon is a through tenon made so that it projects way beyondthe mortise. A wedge is fitted into theprojection which, when driven hard,pulls the shoulder of the tenon tightlyand firmly to the mortised piece. Here’sIan Kirby’s thorough analysis of this jointand the elegant table it produces.

This joint can be designed in a vari-ety of ways, but no matter the variation, a successful joint requires several char-

acteristics common to all:The Shoulders— I’ll begin with

the shoulders on the tenon piece thatform the dead stop that the wedge ispulling against.

You could make the shoulders onthe sides and edges of the tenon asyou would for a normal glued-up tenon.However, the resistance to stresscomes largely from the two outer edges(top and bottom) of the rail and less

from the shoulders on the sides of therail that would normally form the jointline. Indeed, on many tusk tenons youwill find that there are no shoulders onthe sides of the tenon. And there is novirtue in the tenon being a tight fit in its mortise as you would expect in aglued-up joint. In fact, the fit can bequite sloppy and still work well. Aim fora comfortable sliding fit.

The ratio/relationship between the


Table Exploded View

123/4"

289/16"

12"12"

56"

1

10

2

3

4

5

6

7

8

9

11

12

13

14

15

3/4"

15/16"

43/4"

33/16"

22.5°

1

1

2

2

3

4

5

6

31/4"

11/16"

11/16"

31/4"

289/16"

103/8"

CL

11/2"

3/8"

47/16"

3"

1/4"

163/8"

3/4"15

13

11/16"

25/8"

21/16"

1

10

2

3

4

5

6

7

8

9

11

12

13

14

15

17

16

17

13/4"

5/8"

Tusk Tenon Table (Front View)

Folding Wedge(Top and Front Views)

End Frame Assembly(Front View)

Top Board Layout (Top View)

The author selected the mostbeautiful stock to compose his tabletop. Balancing thegrain and figure and steppingeach board out was the keyto its composition.

Rail Subassembly(Front and End Views)

Glue and Screw BlockAssembly(Top and Side Views)

140 HOME PROJECTS WOODWORKER'S JOURNAL ©2007 ALL RIGHTS RESERVED

1

1

1

10

2

23

3

33

4

5

6

6

7

8

8

9

11

11

12

13

13

13

14

15

15

16

17

4


MATERIAL LIST – Table

END FRAMES T x W x L

1 Cap Rails (4) 11/16" x 21⁄16" x 157⁄8"

2 Shoulder Rails (4) 11/16" x 21⁄16" x 10 3⁄8"

3 Inside Legs (4) 11/16" x 21⁄16" x 261⁄2"

4 Leg Blocks (16) 11/16" x 21⁄16" x 21⁄16"

5 Outside Legs (4) 11/16" x 21⁄16" x 261⁄2"

6 Foot Pieces (4) 41⁄4" x 11⁄16" x 21⁄16"

RAILS T x W x L

7 Stretcher Rails (2) 11/16" x 21⁄16" x 313⁄4"

8 Shoulder Rails (4) 11/16" x 13⁄16" x 273⁄4"

9 Rail Extension Strips (8) 9/16" x 11/16" x 43⁄4"

10 Mortise Blocks (4) 11/16" x 21⁄16" x 2"

11 Short Shoulder Rails1 (8) 11/16" x 7/8" x 41⁄2"

12 Dowels (16) 1/4" Dia. x 11⁄2"

WEDGES T x W x L

13 Wedge Blocks2 (8) 11/16" x 21⁄16" x 25⁄8"

TOP BOARDS T x W x L

14 Top Boards (5) 11/16" x varies x 60"

15 Thickener Rails (2) 11/16" x 21⁄16" x 273⁄4"

16 Glue Blocks (6) 11/16" x 21⁄16" x 21⁄16"

17 Screw Blocks (6) 11/16" x 13⁄8" x 21⁄2"

SPACER BLOCKS T x W x L

18 Leg Block Spacer3 (1) 11/16" x 21⁄16" x 31⁄4"

19 Mortise Block Spacer4 (1) 15/16" x 15/16" x 2"

1End angle is 22.5° 3 To position leg blocks2Cut in wedge jig 4 To position mortise block


Technical Drawings

142 HOME PROJECTS

Figure 1: To accurately position the shoulderrails on the cap rails, mark their centers witha marking gauge.

Figure 2: Clamp, drill, and screw the partstogether dry to assist with positioning themonce the glue is applied.

1.Assemblethe cap

andshoulder

rails.

1. Attach shoulder rails to the stretcher rail.

2. Add the rail extension strips. 3. Use dowels to join the mortise blocks to the subassembly.

2.Addthe

insidelegs.

3.Add

the legblocks.

4.Apply finish

to inside legsand blocksand to innerfaces of theoutside legs.

5.Attach

theoutside

legs.

6.Completethe task

byadding

the feet.

Six Steps to Making the End Frames

Four Steps to Making the Rail Assembly

tenon and rail width is something youhave to design, but the wedge and itsmortise play a part in your decision.

The Wedge—The wedge is gener-ally made straight on one edge andtapered on the other edge. The slope ofthe taper is critical. If it’s too steep, thewedge will drive okay but will pop outwhen the assembly is racked—that is,unless it’s been crushed by being driventoo hard. If the slope is too slight, it willpull up the shoulders very tightly, but ittakes too long a wedge to close them.I’ve found that a slope of 12˚ works well.

The Mortise for the Wedge—The outer end wall of the mortise musthave exactly the same slope as thewedge. The inner end wall of the mor-tise must be inboard of the face of theupright leg or stile. Unless the mortise is“oversized,” the wedge cannot bearagainst the upright and pull the shoul-ders tight. (See the Traditional TuskTenon Joint Drawing, page 138.) Thisalso means that the wedge must be

sufficiently beefy to withstand bendingas it crosses the void. And it must besufficiently long so there is plenty ofwedge above and below the void.

The Sheer Load on the Tusk—As the wedge is driven, the shoulderspull up tight. The counter stress istransferred to the extra length of thetenon, the tusk. If the tusk is too short,the wood that is buttressing the wedgewill break out. So another part of yourdesign consideration is how long tomake the tenon to prevent such a col-lapse. Factors include the species ofwood and whether you orient thewedge up-and-down or side-to-side.For example, what would be good forelm, a resistant splitter, would not begood for quartersawn oak.

This joint design was common onearly furniture. It’s probably the moredifficult design to make and the biggerthe parts, the greater the difficulty ontwo counts. First, you have to chop outthe narrow tenon for the wedge and,


Like most woodworking joints, the ancestry of the tusktenon spans millennia and cultures around the world. Wefind it used to hold frames together to make beds andtables, and we find it used to hold boards together to makestorage boxes. There is nothing standard about the dimen-sions of the tenon nor the dimensions of the wedge—theycome in all manner of shapes and sizes. Because it can bemade in so many different ways and can be used on sucha variety of items, it’s probably the most versatile of ourjoint repertoire. As well, it can be used as a temporary jointor a permanent one, and all without the use of glue.

This chest comes from the province of Noorestan inAfghanistan. It belongs to my friend and next-door neighbor,Prince Ali Seraj. It’s believed to be about five hundred years

This massive chestwith its lift-up lid ismade of six pieces ofwood held togetherby six tusk tenons.Despite the wear andtear of the ages, itremains a functioning,practical piece of furniture.

Honest, functional and portable. In less than a minute you couldremove the wedges, part the pieces and pack them on the four-legged transport of your choice.


old, and it’s a perfect example of a large slab structure heldtogether by six tusk tenons.

The ends are two inches thick. Their faces were refinedusing an adze, and the edges are chip-carved with an intri-cate cross ribbon pattern. The lift-up lid has a hinge pivotthat gets trapped in its hole as the ends are wedged inplace. To make the pivot, about two inches of the ends havebeen cut away on the top board to leave a peg, which ismodeled into a cylinder. The four slabs that make up thecase are decorated with fine line carving on every show face.

What I find most interesting are the wedges. They gothrough the thickness of the tenon—the simplest solution—but for the job they have to do, to my mind, they are very thin.

Made to look a bit like a metal spike, the visible wearattests to their having been driven in and removed on manyoccasions. They all appear to be original, and their survivalis a good example of how little we know and respond tothe engineering qualities of this material that we fool our-selves into thinking we have mastered.

The artisans of Noorestan are believed to be some ofthe remnants of the army of Alexander the Great that trekkedthrough that region. Until about 1890, their land was calledKafistan—land of the unbeliever. At that time, they were converted to Islam and had a name change. They remainmakers of furniture and other domestic goods to the nation.

SHORT HISTORY OF A TUSK TENON


144 HOME PROJECTS

Figure 3: Clamp the shoulders tight to thecap and shoulder rail assembly with theinside legs in place.

Figure 5: Glue leg blocks, avoiding squeeze-out, then screw or staple into place. Positioncenter leg blocks using the 31⁄4" spacer.

Figure 6: Glue and clamp the outer leg tothe leg blocks.

Figure 7: Glue and clamp outer legs to theleg blocks, then screw them through the cap rail.

Figure 4: Screw through the cap rail into theend grain of the inside leg. Screws are angledtowards one another for extra strength.

second, you have to get the slope of theend of the narrow tenon to be exactlythe same as the slope on the wedge.

A simpler tusk tenon variation usedto assemble the table featured here, isto make a rectangular hole and use twoidentical wedges, called foldingwedges, as shown in the FoldingWedges Joint Drawing on page 138.

Designed for SimplicityThe underframe of this table is

designed so that it will be very simple tomake while looking like a sophisticatedpiece of joinery.

Two characteristics make it differ-ent from more traditional structures.First, most of the parts are made frommaterial that is the same width andthickness. So you begin with about 50 feet of wood, all milled to dimension,which you then cut up into preciselengths. Second, the cut-up pieces are glued together aided by screws orstaples. Even the holes for the wedgesare made by surrounding a rectangularspace with wood instead of startingwith a solid piece of wood and chop-ping out the square space. In summary,the “joinery” is done by cutting parts tolength and putting them together.

I designed the legs to be squareonce all three elements are put togeth-er, so if you decide to use 3/4"-thick

materials, then the width will be threetimes that—21⁄4". For this side table,which could serve very well as a sofa table, I wanted a slimmer look,so I milled the stock to 11/16" thick and 21⁄16" wide. I’ve no doubt that 1/2" x 11⁄2" material would look mostelegant on the right piece. In otherwords, the dimensions of the stock give you a lot of design flexibility.

Choosing a Wood SpeciesThe species you choose also

plays a big role in the feel that the fin-ished piece projects. For instance, youcould use 3/4"-thick pine with its fairshare of knots and bruises to produce arustic-looking piece. I chose to use flat-sawn sassafras that looks a lot likechestnut and has a very basic woodcolor and appearance. No matter whatyour wood or dimension, begin withenough of it milled to the same thick-ness and width. Overall, you will needabout 55' to 60' max. You’ll have verylittle waste if you cut the long piecesfirst and pick the best-looking stuff forthese parts.

Cutting to Length and PlaningStep 1: Chop the parts to length.

Whether you use a miter saw or a table saw, you must use an end stopin order to produce equal-length parts.


Figure 8: Position the overhang of the footpiece using a sliding head square, thenscrew into place.

Figure 9: Position, glue and clamp rail exten-sion strips with the aid of an alignment block.

Figure 10: Position, clamp and glue themortise block between the rail extensionstrips with the aid of an alignment block (atrear) and a wedge spacer strip.


Figure 11: Position thefirst shoulder rail on thestretcher rail with a screwat each end, then glue andclamp in place.

Figure 12: (right) Position thesecond shoulder rail with the aidof a block clamped tight andsquare to the first shoulder rail.

Step 2: Remove the mill marks byplaning. You can’t do this after assem-bly, so do it now. Use a sharp plane,set fine, and count the same number ofpasses on each piece—it takes aboutthree. Don’t plane the leg spacerblocks, because their slight extra thick-ness lets the rail enter between them.

Step 3: Machine some form ofedge treatment. The square edge is toosharp, and the slightest misalignment ofthe parts looks bad. A chamfer or a

radius solves the problem. I chose a45° chamfer done on a router table. It’s less than 1/16" across the flat, andit’s on all exposed edges.

Joining the End FramesStep 4: Join the cap rail to the

shoulder rail. The shoulder rail is cen-tered in both length and width. Markthe center on both pieces with a mark-ing gauge (see Figure 1 on page 142).Mark the cross grain line on the cap rail

from the end of the rail using a sliding-head try square set to 23⁄4" (21⁄16" leg and11/16" overhang). Clamp the two partstogether dry, then drill and countersinkthe holes for two 15⁄8" screws. Drive thescrews dry and remove them (seeFigure 2). Roll glue onto the edge of theshoulder rail. Limit the glue so there ispractically no squeeze-out. Put theparts back together using the alreadylocated screw holes and they will centerin the correct place. Clean up any glue


146 HOME PROJECTS

A TALE ABOUT THE INSPIRED POWER OF FOLDING WEDGES

Folding wedgesare nothing new in theworld of woodworking, espe-cially to kitchen and architecturalinstallers for raising and levelling cabinets.

I well remember a colleague during my stu-dent years who was making a writing table that wasa solid case about 45" long, 18" wide and 4" deep,joined by secret mitered dovetails at all corners. The casewas to be mounted on a typical four-legged base with stretcher rails.

In his enthusiasm to check the fit of the dovetails, he hammered them all home.They were perfect—and tight! How to disassemble the case now became a nightmare,because it was impossible to get into a 4" space with a hammer and block to part the joints. We pondered the problemto no avail. The ever-present tutor, after chuckling over the dilemma and our inability to solve it, provided the “obvious”solution: folding wedges. A few hearty taps with the wedges installed provided just the right force to separate the parts.

squeeze-out from here on as you go. Step 5: Attach the inside legs.

Clamp the frame of the leg and cap rail assembly together so the shouldersare tight (see Figure 3). Screw throughthe cap rail into the end grain of the leg.I used two 15⁄8" screws angled together.(see Figure 4). Remove the clamps andscrew through the inside leg into theend grain of the shoulder rail.

Step 6: Glue in the leg blocks.There are four blocks to each leg. Twogo tight to the corners and two arepositioned 31⁄4" apart by the leg block

spacer (see Figure 5). Aim to have noglue squeeze-out. Paddle a small circleof glue onto each surface, then pressthe leg block in place—you can lift it offto assess the spread. Align the legblock with a straightedge, then screwor staple it in place. Screws will hold theleg block in place and clamp it as well.A staple will hold the leg block in posi-tion but give marginal clamping. If youuse staples, clamp the corner legblocks using a bar clamp and the center leg blocks with a C-clamp.

Step 7: Apply finish to the inside of

the legs. I used a sealer coat of a dryingoil followed by beeswax. Mark the out-side leg at the glue areas and keep finishoff all faces that will be glued.

Step 8: Attach the outer legs asshown in Figure 6. Glue the blocks andthe legs and clamp them like Step 6.Clamp the end blocks with a bar clampand put two screws through the cap railinto the end grain of the outer leg (seeFigure 7).

Step 9: Attach the feet. Positioneach piece with a 11/16" overhang andscrew it into place (see Figure 8).


Figure 14: The hidden parts of the joint canbe reinforced with staples. A dowel is better.

Figure 15: Glue and clamp the short shoul-der rail flush to the shoulder rail.


Figure 13: Saw off the excess length ofdowel before cleaning flush with a chisel.

Joining the RailsStep 10: Attach the shoulder rails

to the stretcher rail. Mark centers onboth parts using your marking gauge.Score a line 2" from the end. The shoul-der rail should fit between the marksand leave a 1/16" pull-up space in themortise so the wedges can work. Toattach the shoulder rails one at a time,begin by clamping one in place dry andput in screws about 2" from each end(see Figure 11). Remove the screwsand roll a conservative layer of glue onthe edge of the stretcher rail. Screw thetwo parts back together, which shouldretain your centers and clamp the mid-dle area. To position the second shoul-der rail, clamp an alignment blocksquare to the first shoulder tail at eachend (see Figure 12). Position the sec-ond shoulder rail. Dry-screw and glueas you did for the first one.

Step 11: Attach the rail extensionstrips (see Figure 9). Clamp the samealignment block as you used in Step 10to the end of the stretcher rail. Glue theextension strips, align and clamp them.

Step 12: Attach the mortiseblocks. Clamp the alignment block tothe extension strips and trap the wedgegap block in place with it (see Figure10). Put glue on the mating contactfaces of the extension strips and themortise block. Clamp them in place.

Step 13: Peg the extension strips.I have no laboratory or field tests toprove how necessary or effective thesereinforcements might be, but they feelright. You can staple the hidden area(see Figure 14), or you can use a dowelto peg the extensions to the stretcherrail and the mortise block. It’s importantto use a Forstner bit to make the 11⁄4"-deep hole. Drizzle some glue into thehole and wet the end of the dowel.Push the dowel home hard to forceglue from the bottom of the hole. Twist

the dowel to wet the walls of the hole.Saw off the dowel and clean up with achisel (see Figure 13).

Step 14: Attach the short shoulderrails. Attach one and let it cure beforeyou do the second (see Figure 15).Paddle a mean amount of glue on theshort shoulder rail. Hold the stretcher railin the vise, press the short rail in placeand rub it about 1/2" up and down tospread the glue and wet both faces. Pullit off and add dabs of glue where need-ed. Rub it into place again and positionit using a straightedge taken from yourtry square. Center it by eye. Clamp itand check the shoulder again.

Making the WedgesThe wedges are made using a jig

and a chop saw. The wedge blocks aremade from the 21⁄16"-wide stock cut to25⁄8" long. You need two of these blocksto make the jig. I used some 1/2" mapleplywood and cut four strips 2" x 12".The strips are stapled or screwed to theblocks, which are set square 11/16"from the ends. Set your miter saw to12°. Position the box so the cut willleave a full 11/16" thickness at one endand a full 1/8" flat at the other. It’simportant to clamp the wedge boxsecurely to the fence and the bed of thesaw (see Figure 18). The wedge blocksfit tightly into the end pocket of the jig.Once you’ve made the first cut, youunderstand why the box is made withexposed corners. To remove thewedge, pry carefully, first with the bladeof the knife, followed by a screwdriver.(see Figure 17). The wedges are cham-fered on the exposed edges and ends.(see Figure 16).

Making the TopThe overall dimensions of the top

are 56" x 163⁄8" x 11/16". I wanted thedrama of the 12"-long end overhang


148 HOME PROJECTS

Figure 19: The top is secured and fixed oncenter by blocks that trap one flange of thecap rail while allowing for shrinkage andexpansion.

Figure 18: Clamp the jig tight to the bed andfence of the chop saw. Holding it by hand isneither safe nor accurate.

Figure 16: All exposed ends and edges arechamfered, including the wedges.

Figure 17: Make the wedge jig using twowedge blanks and strips of 1/2" plywood.The narrow strips allow access to the cornerof the wedge to pry it out after cutting (seeinset).

and the minimal 1/4" edge overhang inorder to let the base be as visible aspossible. The top dimensions alsomake for an elegant rectangle.

We all have to compose tops fromthe boards at hand. I had three whosegrain went together the best but weretoo narrow by an inch. The solution was to split the center piece and insertthe 11⁄2" strip to make up the extrawidth. To make some visual connectwith the step and shadow effect of the

to shrink and expand past the outerscrew blocks.

With this done, you’ve nowaccomplished two important goals:You’ve delved into the intricacies ofmaking tusk tenons and also have atable to show for your efforts.

rail and tenon, I stepped the end of theboards. To help make the different grainpatterns come together better and toelongate the look of the top while keep-ing in step with the edge detail on thebase, I chamfered the top boards allround to complete it.

Connecting the Top to the BaseThe top has two 11/16" x 21⁄16"

x 273⁄4" thickener rails glued to it that fitsnugly between the legs and arealigned with the ends of the cap rails.As well as positioning the top, they create a visual tie between the top andthe base.

I used a variation on the traditionalbutton method to hold the top to thebase. Three 11/16" x 21⁄16" x 21⁄16" glueblocks are glued to the top on theinside edge of each cap rail. (see Figure19). Screw an 11/16" x 13⁄8" x 21⁄2" blockto each glue block so that it traps theoverhang of the cap rail. The centerscrew block also has a screw into thecap rail that registers the top so it’scentered on the base but leaves it free



JOINT VARIATIONS

The hole and dowel joint appliesall the tusk tenon principles tohold this angled leg and railassembly tight on this mock-up ofan Arts & Crafts-inspired table.

The wedge on the left is too narrow: it willbend into the pull-up space—or break.The wedge on the right is sized correctly.

Two identical joints, but the wider shoul-ders of the one on the right make itstronger because of triangulation.

The horizontal wedge on the right is easierto make as there is less wood to cutthrough. The vertical wedge on the left ismore difficult to form.

In this variation,the wedgeencloses thetenon instead ofpiercing it. Thedowel acts as adead stop.

Side Views

Side Views

Side Views

Top Views

Top Views

In the “History of the Tusk Tenon”sidebar, I noted that the joint is used tohold together all manner of furnitureforms, but there is nothing standardabout its design details. You can designit any way you want, provided the wedgepulls up the shoulders and stays tight.

Vertical WedgeIn the traditional version of the joint,

you can vary the shape and dimensionsof the parts, but the wedge must bemade wide enough so that it won’tbend or break in the “pull-up” space of wedge hole.

Horizontal WedgeTo avoid the complication of

making a deep narrow hole for thevertical wedge, you can make thewedge go horizontal. It works equallywell, and it adds a more “locked-up”appearance to the joint.

Outside WedgeYet another variation is an external

wedge and a hole with a dowel as thedead stop. A flat on the dowel givesthe wedge a larger contact surfaceand improves its overall appearance.


tusk tenon table — synchronized simplicity · 2019. 4. 9. · synchronized simplicity harness the...

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