Box Joint Jig - Chuck's...

Box Joint JigBox Joint JigThis shop-made jig lets you “dial in” perfect-fitting box joints on your table saw or router table.The unique micro-adjustment system and locking feature make it easy and accurate.

The thing that impresses me mostabout this box joint jig isn’t thetight-fitting joints you can make

with it. After all, that’s what you expectfrom a precision-made jig. What’sunique is how quickly and easily it canbe adjusted.

Unlike most box joint jigs I’ve usedthat require an almost endless amountof “tweaking,” this jig can be set up in amatter of minutes. The secret is a built-in system that lets you adjust the jig inextremely small increments.

MICRO-ADJUSTMENT SYSTEM. Thissystem is designed to adjust both thesize and spacing of the pins and slotsthat make up a box joint. By simplyturning a knob, the jig can be set to cut

securely in place. The result is perfectfitting box joints.

TWO TOOLS. Another nice feature ofthis box joint jig is that it can be usednot only on the table saw (see largephoto above), but also on the routertable (see inset photo).

MATERIALS. With the exception of a1/4" hardboard backing plate, all themain parts of the box joint jig are madefrom 1/4" or 3/4"-thick hardwood.

slots that range in size froma width of 1/4" to 13/16". Asecond knob changes thespacing of the pins andslots. This tightens (orloosens) the joint whichallows you to sneak up on aperfect fit.

KEY. The adjustment system worksby moving two metal brackets. Thebrackets form a “key” that automati-cally positions the workpiece so eachslot is cut a uniform distance apart. Thiscreates a series of pins and slots that fittogether like fingers in a glove.

LOCKING FEATURE. To prevent thekey from “creeping” once it’s beenadjusted, a pair of plastic knobs locks it

ShopNotes.com page 1 © August Home Publishing Co.

Plans N O W

EXPLODED VIEWOVERALL DIMENSIONS:4W X 191/4L X 61/4H

WOODA Fence (1) 3/4 x 51/2 - 18B Backing Plate (1) 1/4 hdbd. - 11/2 x 51/2C Fixed Mat. Rest (1) 3/4 x 11/2 - 113/8D Movable Mat. Rest (1)3/4 x 3 - 53/8E Front Adj. Block (1) 3/4 x 2 - 61/2F Back Adj. Block (1) 3/4 x 2 - 53/8G End Plate (1) 1/4 x 2 - 21/4

HARDWARE SUPPLIES(5) No. 6 x 5/8" Fh woodscrews(2) No. 8 x 3/4" Rh woodscrews(1) 1/4" x 1" machine screw

(3) 1/4" - 20 plastic star knobs(3) 1/4" flat washers(2) 3/4" x 4" L-brackets*(1) 1/4" x 11/2" carriage bolt(1) 1/4" x 21/2" carriage bolt(2) 10-32 threaded inserts(4) 10-32 washers (brass)(2) 10-32 lock nuts(2) 10-32 hex nuts (brass)(2) 10-32 knurled knobs (brass)(2) 10-32 threaded rods - 21/2" (brass)* Also sold as mending plates

MATERIALS LIST

A

G

E

F

B

CD

KNOBS "LOCK IN"ADJUSTMENT

!/4" - 20 PLASTICSTAR KNOB

TOP VIEW

REPLACEABLEBACKING PLATE

REDUCESCHIPOUT

BACK ADJUSTMENTKNOB CHANGES KEY TO

FIT SIZE OF SLOTS

FRONT ADJUSTMENTKNOB CHANGES SPACE

BETWEENSLOTS END PLATE

!/4" !/2"x 1CARRIAGE BOLT

METAL BRACKETSFORM ADJUSTABLE KEY

A

G

E

FB

C

D

!/4" - 20PLASTIC

STAR KNOB

BACKADJUSTMENT

BLOCK

FRONTADJUSTMENT

BLOCK

#/4" x 4"L-BRACKETS

!/4" FLATWASHER

#8 xRh WOODSCREW

#/4"

END PLATE

MOVABLEMATERIAL REST

10-32THREADED

INSERT

FENCE

#6 x FhWOODSCREW

%/8"

BACKINGPLATE

!/4" x 1"MACHINE SCREW

FIXEDMATERIAL

REST!/4" !/2"x 2

CARRIAGE BOLT10-32

LOCK NUT10-32

WASHER

10-32HEX NUT

10-32KNURLED KNOB

10-32THREADED ROD

(2 -LONG)!/2"


WOODSMITH PROJECT SUPPLIES isoffering a kit that contains all the hardwarefor this jig (you supply the wood).

Call 1-800-444-7527 and ask about kit no.6808-100.

HARDWARE KIT

A

B

CD

NOTE:CUT DADO -DEEP!/4"

!/4" - 20 PLASTICSTAR KNOB

CUT CHAMFERON TOP CORNERS

!/4"

MOVABLEMATERIAL

REST

NOTE:DRILL COUNTERSUNK HOLE

IN BACKING PLATE

BACKING PLATE

FIXEDMATERIAL REST

DRILL -DIA.HOLE CENTERED

ON DADO

#/8"

NOTE: FENCE ISMADE FROM -

THICK STOCK#/4"

FENCE(5 x 18")!/2"

!/4" x 1"MACHINE SCREW

5!/2

1!/2

1

C

D

SECOND: CROSSCUTPIECES TO LENGTH

THIRD: TRIM FIXEDMATERIAL REST TO WIDTH

WASTE

WASTE

FIRST:RABBET EDGE MOVABLE

MATERIAL REST

FIXEDMATERIAL REST

18

5#/8

11#/8

#/4

#/4

!/4

1!/23

2

FENCE

The box joint jig is designed with a tallfence that supports a workpiece whenyou stand it on end. This lets you cutslots on the end of the workpiece bypushing the jig through the table sawblade (or router bit).

FENCE. The fence (A) is just a piece of3/4"-thick hardwood (maple) with thetop corners chamfered (Fig. 1). To pro-vide plenty of support, the fence is 51/2"tall (wide) and 18" long.

BACKING PLATE. After you’ve cut thefence to size, the next step is to add areplaceable backing plate. This platewill help prevent the wood fibersaround the back of the slot from chip-ping out as the blade passes throughthe workpiece.

So why doesn’t the fence alone solvethe problem of chipout? It will, but onlythe first time the jig is used. Because asthe jig passes over the blade, a slot is cutin the fence itself as well as in the work-piece. Once that slot is cut, you’veremoved the support.

That’s where the backing plate (B)comes in. It’s just a piece of 1/4" hard-board that fits in a shallow dado in thefence (Fig. 1).

To make it easy to replace when itgets chewed up, the plate is held inplace with a machine screw and knob(or wing nut) (Fig. la).

Note: If you cut a lot of box joints,you should cut a few extra backingplates now to have on hand later.

MATERIAL REST

With the fence complete, the next stepis to add a material rest. The materialrest serves as a “shelf” that raises theend of the workpiece above the saw orrouter table.

Because it’s raised above the table,the workpiece spans any irregularitiesin the table insert that can cause thedepth of the slots to vary.

TWO PARTS. The material rest con-sists of two separate parts. The first is afixed rest (C) that’s attached perma-nently to the jig. The second is a mov-able material rest (D) that slides fromside to side (Fig. 1).

This two-part rest creates anopening that provides clearance for anadjustable “key” that’s added later(refer to next page).

The two-part design also lets youslide the jig through the blade withoutcutting into the material rest.

BLANK. Both parts of the materialrest are cut from one 3/4"-thick blank(Fig. 2). After cutting a rabbet on oneedge to form the shelf, the two parts arecut to final length.

Then the fixed rest is trimmed towidth (11/2") and glued to the bottom ofthe fence (Fig. 1). The movable rest willbe used later as a platform for theadjustment system.

FENCEBACKING

PLATE

!/4" FLATWASHER

!/4" - 20PLASTIC

STARKNOB

!/4" x 1"MACHINE

SCREW

NOTE:GLUE FIXEDMATERIALREST FLUSHWITH BACKOF FENCE

DRILL -OVERSIZED

ADJUSTMENTHOLE

#/8"

FIXEDMATERIAL

REST

a.


E

F

BACKADJUSTMENT BLOCK

#/4" x 4"L-BRACKETS

!/4"WASHER

MOVABLEMATERIAL REST

NOTE: GLUE BACKADJUSTMENT BLOCK FLUSHWITH BACK AND END OFMOVABLE MATERIAL REST

FRONTADJUSTMENT

BLOCK


FENCE


3

BACK ADJUSTMENT BLOCK

FRONT ADJUSTMENT BLOCKTO LOCATE HOLE,REFER TO FIG. 6

2

2

1#/8 1!/2

2#/4

&/8

5#/8

2#/8 !/2

&/8

6!/2

4

FRONTADJUSTMENT

BLOCK

MOVABLEMATERIAL

REST

TRIM BOTTOMENDS TO FIT

BACKADJUSTMENT

BLOCK

FIRST: TRIM TOPENDS OF L-BRACKETS

TO FIT BLOCKS

SECOND: DRILLHOLE DOWNFROM TRIMMED

ENDS

#/8"

#6 x FhWOODSCREW

%/8"

EXISTING HOLENOT USED

3

2#/4

2!/4

5

ADJUSTMENT SYSTEM

After completing the material rest,work can begin on the adjustmentsystem. This is the part of the jig thatlets you make micro-adjustments to thesize of the box joints you’re cutting.

Basically, this system consists of themovable material rest you cut earlier,two adjustment blocks, and a pair of L-shaped metal brackets (Fig. 3). Theblocks and brackets work together toform a “key” that adjusts to the desiredsize and spacing of the slots that makeup the box joint.

CUT BLOCKS. Start by cutting thefront adjustment block (E) and the backadjustment block (F) to size from 3/4"-thick stock (Fig. 4).

Note: The back adjustment block iscut to match the length of the movablematerial rest (D), but the front adjust-ment block is longer (61/2").

ADJUSTMENT SLOTS. To make thekey adjustable, slots are cut in the front(E) and back adjustment blocks (F)(Fig. 4). Then the back block is glued tothe movable material rest (D) that wasmade earlier to create an L-shapedassembly (Fig. 3).

KEY. When the glue dries, the nextstep is to add the adjustable key. To dothis, the L-brackets are attached to theends of the blocks. These brackets arejust 4" mending plates that I picked upat the local hardware store.

The only unusual thing is thebrackets need to be modified slightly tofit the adjustment blocks. This requires

trimming the ends and drilling an addi-tional mounting hole in each bracket(Fig. 5). Note that the legs of thebrackets are two different sizes.

ATTACH BRACKETS. Now the bracketscan be screwed to the ends of the twoadjustment blocks so the bottom “legs”

are flush with the front edge of thematerial rest (D). After the adjustmentsystem is assembled, the legs willextend in front of the fence and form thekey that’s used to position the work-piece (refer to Fig. 3a).

A

EF

D

!/4" - 20PLASTIC STAR

KNOBFENCE

“LEGS” OF BRACKETS FORM KEY

a.


POSITION FRONT BLOCKFLUSH WITH END OF

MATERIAL REST

MATERIALREST

BACKADJUSTMENT

BLOCK

6

FIRST: SLIDE BLOCKS ALLTHE WAY TO THE LEFT

SECOND: MARK HOLEAT END OF SLOT

FENCE

7

UPRIGHT

SUPPORT

BASE

NOTE:JIG MADE FROM

-THICK STOCK#/4"

4

56

SHOP JIG . . . . . . . . Vertical Drilling GuideHolding a long workpiece (like the

box joint jig) steady when drillingholes in end grain can be a challenge.So when I drilled the holes for theadjusting rods, I decided to build asimple jig (see photo).

It’s nothing more than a couple ofpieces of wood, held together at a rightangle, and a triangular support piece(see drawing).

To center the hole on the bit, thebase is clamped to the drill press tableso the upright extends over the edge.Then, with the work clamped to theupright, loosen the table and swing theworkpiece under the bit.

LOCKING SYSTEM

The two adjustment blocks (E, F) allowyou to set the size and spacing of thekey. To prevent this key from movingonce it’s adjusted, I installed a speciallocking system.

This system consists of two separate“locks” — one for the size of the key,and one for the spacing between the keyand the blade.

SIZE LOCK. To lock in the size of thekey, the adjustment blocks are heldtogether with a carriage bolt and knob(refer to Fig. 3a).

The bolt passes through a holedrilled in the front block (E) andthrough the short slot in the back block(F) (Figs. 6 and 6a).

TEMPLATE. To ensure the hole in thefront block aligns with the slot, I usedthe back block as a template (Fig. 6).With the ends of the blocks flush, a 1/4"brad point bit can be used to mark thecenter of the hole at the end of the slot(Figs. 6 and 6a).

DRILL HOLE. After locating this cen-terpoint, drill a shank hole for the car-riage bolt.

Then to recess the head of the bolt, Iused a Forstner bit to drill a counter-bore (I made this 3/4"-dia. counterbore1/4" deep).

Now the two adjustment blocks canbe fastened together with a carriagebolt, washer, and plastic knob (or wingnut) (Fig. 7).

SPACING LOCK. The next step is toprovide a way to lock in the spacing

between the key and the blade. Hereagain, a carriage bolt is used. But thistime it passes through a hole in thefence and the long slots in both adjust-ment blocks.

To locate this hole, place theassembly under the fence. Then slide

the blocks to the left as far as possible,and make a mark for the hole at the endof the slot (Fig. 7).

All that’s left is to drill a counter-bored shank hole in the fence (Fig. 7a).Then install a carriage bolt, washer, andknob as before.

E

F

D

FRONTADJUSTMENT BLOCK

DRILL -DIA.COUNTERBORE

-DEEP

#/4"

!/4"

MARK HOLE LOCATION WITHBRAD POINT BIT!/4"

a.

A

EF

D

DRILL -DIA.COUNTERBORE

-DEEP

#/4"

!/4"

a.


G

2 -LONG 10-32THREADED ROD

!/2"

10-32 KNURLED KNOB

HEXNUT 10-32

LOCK NUT

10-32 WASHER

#8 x RhWOODSCREW

#/4" END PLATE

10-32THREADED

INSERT

8

#/16" BRADPOINT BIT

FIRST:DRILL HOLESIN END PLATE

SECOND:USE PLATE ASTEMPLATE TOLOCATE HOLES

ON JIG

THIRD:REMOVE

PLATE ANDDRILL HOLES

DRILL PILOTHOLES FORMOUNTING

SCREWSSIZE HOLESTO FIT INSERT

9

SECOND:POSITION END OF

FIXED MATERIAL RESTAGAINST BLADE

THIRD:SCREW MITER

GAUGE TO FENCE

FENCEFIRST: MOUNT

LARGEST DADO BLADE

MITER GAUGE

10

MICRO-ADJUSTMENT SYSTEM

The most innovative (and useful) fea-ture of the box joint jig is the micro-adjustment system. This system letsyou “fine tune” the key to the desiredsize and spacing of the slots.

ADJUSTING RODS. The secret to thissystem is a pair of adjusting rods. Onerod threads into the end of the backadjustment block, and the other rodthreads into the fence (Fig. 8).

By turning these adjusting rods, youslide the adjustment blocks from side toside, which positions the key. (For moreon using the micro-adjustment system,see page 7.)

ADJUSTMENT ASSEMBLY. To makethis system work, an adjustmentassembly is attached to the front adjust-ment block (E) (Fig. 8). This assemblyconsists of a thin wooden end plate andseveral pieces of hardware.

END PLATE. Before installing thehardware, I cut an end plate (G) from apiece of 1/4"-thick hardwood (Fig. 9a)to dimensions of 2" x 21/4". Then, four3/16"-dia. holes are drilled through theend plate.

After drilling these holes for theadjusting rods and two mountingscrews, the plate can be used as a tem-plate to mark the corresponding holesin the end of the jig (Fig. 9).

DRILLING JIG. Marking these holes inthe end of the jig is the easy part. Thetrick is actually holding the jig steady todrill the holes. Since this part of the jigwill be used to make micro-adjust-ments, you want to make sure the holesare drilled accurately.

To do this, I built a simple drilling jig(see the Shop Jig box on the previouspage). Once the holes are drilled, themicro-adjustment system can be assem-bled as shown in Fig. 8.

The 21/2"-long adjusting rods are cutfrom a piece of 10-32 threaded rod. Toaccept these adjusting rods, threadedinserts are installed in the fence (A) andback block (F). The actual adjustingpressure is created by a “stop” on each

side of the plate.The stop on the inside of the plate is

a washer and lock nut (Figs. 8 and 8a).Another washer and a knurled knobthat’s tightened against a nut forms theoutside stop.

MITER GAUGE

The last step is to attach the jig to themiter gauge. The idea here is to posi-tion the jig so you can cut the largestpossible slot without cutting into thematerial rest.

This requires mounting your widestdado blade (or largest bit, if you plan onusing the router table). In my case, thiswas a 13/16" dado blade (Fig. 10).

Note: Since I don’t like to removethat much material with a router (forsafety reasons), the largest router bit Iuse is a 1/2" straight bit.

To complete the jig, check that themiter gauge is square to the blade.Then position the fixed rest against thesaw blade, and screw the gauge to thefence (Fig. 10a).

Note: If you prefer, you can usemachine screws and threaded inserts tomount the jig. ■

A

E

F

TOP VIEWBACK

ADJUSTING ROD

FRONTADJUSTING ROD

DRILL 2"-DEEPHOLE TO FIT

INSERT

a.

END PLATE DIMENSIONS

!/4"-THICKSTOCK

DRILL ALLHOLES

DIA.#/16"

#/8

2

#/8%/8

2!/4

a.

FENCE

FIXEDMATERIAL

REST

a.


TECHNIQUE . . . . . . .Making Box Joints

RAISE BLADETO MATCH

THICKNESS OFWORKPIECE

FIRST: CUT SLOTIN TEST PIECE

SECOND: ADJUSTKEY TO FIT SLOT

TESTPIECE

POSITION KEYTHE WIDTH OF

ONE SLOT AWAYFROM BLADE

Basically, there are only two require-ments for making accurate fitting

box joints. The first is perfect spacingbetween the pins and slots. The secondis getting the ends of the pins flush withthe side of the adjoining piece (seephoto at right).

Using the micro-adjustable box jointjig solves the first problem — cuttingidentically spaced pins and slots.

FLUSH PINS. But the jig itself onlyhelps so much. In order to solve thesecond part of the problem (getting the

ends of the pins flush with the side ofthe adjoining piece), there are twoother things you’ll need to take intoaccount: the length of the pins and thethickness of the workpieces.

In an ideal situation, the length of thepins would match the thickness of theworkpieces exactly. So start out bychecking that all the pieces are thesame thickness.

Note: While you’re at it, “thickness”a few test pieces to use when adjustingthe jig.

1 To produce a box joint with the endsof the pins flush with the side of the

adjoining piece, raise the blade to matchthe thickness of the workpiece.Note: This is the distance from thematerial rest to the top of the blade.

2 Using a slot cut in a test piece, thekey is adjusted to match the width of

the slot. To do this, loosen the lockingknobs and turn the back adjustmentknob until the slot fits snugly over thekey. Then tighten the outside lockingknob.

3 Now turn the front adjustment knobto set the spacing between the slots.

After positioning the key the width ofone slot from the blade, tighten theinside knob. Then make a test joint andreadjust if necessary. Moving the keycloser to the blade loosens the joint.Moving it away tightens the fit.

KEY

THICKNESS OFWORKPIECE

MATERIALREST

DADO BLADE

a.

TURN TO ADJUST SIZE OF KEY

TIGHTEN KNOB TO LOCK KEY

ADJUST KEY TO MATCH SLOT

a.

TIGHTEN KNOB TO LOCK IN SPACING

TURN TO ADJUST SPACINGBETWEEN KEY AND BLADE

a.


SECOND:FIT JUST-CUT SLOTOVER KEY TO CUTNEXT SLOT

WASTE

FIRST:POSITION EDGE OF

WORKPIECE AGAINSTKEY TO CUTFIRST SLOT

KEY

FLIP WORKPIECETO CUT MATCHINGSLOTS ON OTHER END

NOTE:HOLD WORK TIGHT

AGAINST FENCE ANDMATERIAL REST

WASTE

FIRST:TURN WORKPIECEAND FIT FIRST-CUTSLOT OVER KEY

WASTE

SECOND:POSITION MATING PIECEAGAINST EDGE OF FIRSTPIECE AND CUT SLOTS

THIRD:TRIM WASTE

After checking the thickness of allthe pieces, the next step is to determinethe length of the pins (in other words,the depth of cut).

To do this, I use a test piece (thesame thickness as the workpieces) as aset-up gauge. I then raise the blade tomatch the thickness of the piece (referto Step 1). Then I use a slot cut in thetest piece to set the width of the key. andadjust the spacing (Steps 2 and 3).

APPEARANCE. While it doesn’t “makeor break” the box joint, I like the look of

a full pin (or slot) on the end of eachpiece. So I cut each board to length, butdecided to leave the boards actuallywider than necessary for the project I’mworking on. Then, after completing allthe slots, the extra width can betrimmed to leave a full pin (or slot) atthe end.

Note: Marking the extra width (as“waste”) helps keep track of which edgeto position against the key (Steps 4through 6).

TRIAL JOINTS. Once the pieces are

cut to “working” size, it’s a good idea tomake a trial joint.

The goal is to slide the pins into theslots with a “friction” fit (they shouldrequire a few light taps to cometogether, but not be so tight that youneed to force them). This may requiresome readjusting of the jig to get a per-fect fit. But the end result will be worththe effort.

MAKE JOINTS. Now it’s just a matterof cutting matching slots on each work-piece (Steps 4 through 6).

4 With the edge of the workpieceagainst the key, cut the first slot. This

creates a pin on the end of the piece.Then position the workpiece to cut eachof the remaining slots by straddling thekey with the slot that was cut last.

5 To cut matching slots on the oppositeend, flip the workpiece so the waste

edge is oriented to the same side. Then,with the work held firmly against thefence and the material rest, cut slots onthe opposite end of the workpiece,using the same procedure as before.

6 To form pins that match the slots onthe adjoining piece, use the first

piece as a setup gauge. Just turn itaround so the waste edge is on theopposite side and the slot that was cutfirst fits over the key. After cutting thefirst slot on the adjoining piece, set thefirst piece aside and complete the boxjoint.


Box Joint Jig - Chuck's...

Documents

Transcript of Box Joint Jig - Chuck's...