D4Ch08 - Leigh Dovetail Jigs and Mortise Tenon Jigs | D4R Pro … · 2018. 6. 21. · Title:...

Through Dovetail Procedures

CHAPTER 8

Chapter 8 D4 User Guide

Chapter Foreword In these instructions for using the LeighDovetail Jig, we have recommended usingcertain cutters and board sizes just becausethey are easy to work with. When you havecut some practice joints and gained con-fidence in your ability to get the results youwant, feel free to use the guidebush andcutter selection charts on pages 149 and155 to plan whatever dovetail routing youneed for your own projects.

T H R O U G H D O V E T A I L P R O C E D U R E S52

8-1Through Dovetail Terminology:➀ Pins ➁ Pin sockets ➂ Half-pins ➃ Half-pin sockets ➄ Tails ➅ Tail sockets The pins fit in the pin sockets. Joints almostalways end each side with half-pins.

8-2Let’s look at how to make a simple squarebox.

8-3You will need five identical boards 3⁄4"x5-1⁄2"[20x140mm] x 8"[200mm] or so long(the fifth board may be used up doing theinitial testing for fit). Mark the insideand outside faces of each board. For thistrial use a router with a 7⁄16"[11,1mm] O.D.guidebush and a No. 80 or 80-8 1⁄ 2"[12,7mm]x 8° dovetail cutter and a No.140or 140-8 5⁄16"[7,9mm]straight cutter (seethe cutter and guidebush selection chartsin the appendix).

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8-4Fit the 7⁄16"[11,1mm] guidebush securelyto the router.

8-5Fit the 80 or 80-8 dovetail cutter to therouter.

8-6Clamp the spacer board in the rear clamp. To simplify the instructions, some illus-trations will show a jig considerably short-er than the standard 24"[610mm] jig.



8-7Place the finger assembly on the supportbrackets in the dTD PINS mode, flat onthe spacer board, and with the scale seton the 1⁄2"[12,7mm] setting for now. Don’tworry about the scale’s specific meaningnow. Each scale’s use will be fully explainedin the appropriate section.

8-8Although you will cut the tails first, adjustthe guidefinger layout in the dTD PINSmode. The adjustment screws are on topin this mode, and it is easier to visualize thefinished joint pattern. Clamp one of thepin boards in the left side of the front clamp,against the side stop, with the top edge flushunder and touching the guidefingers,and the outside face o away from the jig body.

8-9Loosen the support bracket knobs and raisethe finger assembly about 1⁄16"[2mm] ➀above the boards and retighten the knobs.This will allow easy and accurate guidefin-ger adjustment.

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8-10The following joint design is only a sug-gestion for this trial. It has a typical and tra-ditional symmetrical layout of pins, withhalf-pins at each edge. The Leigh jig, how-ever, allows for an infinite variety of jointdesigns, and boards of different thickness-es can also be joined to each other as shownin this illustration. Before attempting jointsof asymmetrical design, please see chap-ter 13.

8-11Ignoring the extreme outer guidefinger nextto the scale (it just supports the router),loosen the next eight guidefingers and slidethem over the top of the workpiece.

8-12Lock the left-most half-pin guidefingerabout 1⁄8"[3mm] ➀ in from the left edgeof the board.

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8-13Leave three pairs of guidefingers over theboard and lock the right-most half-pinguidefinger about 1⁄8"[3mm] ➁ in fromthe right edge of the board. Judge this dis-tance by eye: it need not be exact. The sock-ets and pins will align automatically.

8-14Space and lock the three remaining pairsas shown. Again, judge it by eye. If it looksright on the jig, the finished joint will look right.

8-15Tighten any other loose guidefingers andremove the pin board.

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8-16Rotate the finger assembly to the DTDTAILS mode, and set it to the ≤1"[≤26mm]position on the scale. Lower the fingerassembly onto the spacer board. All TDtails are routed at this ≤1"[≤26mm] set-ting.

8-17Clamp the tail board vertically, with theinside i face of the board away from thejig.

8-18Place the end of a pin board horizontallyflush under the guidefingers and mark athin pencil line partly across the tail board.

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8-19Remember to follow all safety precautionswhen routing.

8-20Place the router on the finger assembly andadjust the router until the dovetail cuttertip is level with the centre of the pencil line.Note: This means the pin socket will be halfa thin pencil line deeper than the thicknessof the pin board, leaving minimal clean-upafter assembly.Check to make sure the cutter rotates freely.

8-21Plug in the router and rout out the half-pinand pin sockets. Use only light side pres-sure on the guide fingers. Take care not torout unwanted sockets where there are gapsbetween the pairs of fingers ➀. Rout onlybetween the rounded guidefinger tips. See17-19 in Hints and Tips.Before removing the routed board from thejig, check by eye and touch to make sureno parts have been missed. See page 143 forHints and Tips on how to minimize tearout.

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8-22Release the clamp and reverse the tail boardin the jig, keeping the same inside face iaway from the jig body.

8-23Rout the other end of this tail board andboth ends of the second tail board in thesame fashion.

8-24Rotate the finger assembly to the dTDPINS mode. Do not change the guidefin-ger layout.



8-25The tightness of the finished joint is determined in the dTD PINS mode. The farther outtoward the operator the finger assembly is set, the larger the pins will be. Setting the finger assem-bly farther in will make the pins smaller. (The outer, non active support finger is not shown inthis illustration).

8-26The TD Pin scale ➀ looks like a pin. Thedimensions in this pin-shaped panel indi-cate the width of pin to be routed. Thesedimensions match the size of dovetail cut-ter used to rout the tails. Manufacturingtolerances of routers, cutters and guide-bushes make it impossible to predict exactsettings. So set the scale two divisions abovethe required setting (two divisions abovethe 1⁄2"[12,7mm] setting in this example).This should result in oversize pins for thefirst test. (The narrow central panel ➁ issimply a reminder of the straight cutterdiameter required for various pin widths.)

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8-27Clamp a test pin board against the left handside stop, outside face o away from the jig,with the top end flush under the guides.

8-28Place the side edge of one of the tail boardshorizontally flush under the guidefingersand mark a thin pencil line part way acrossthe pin board.

8-29Unplug the router and remove the dove-tail cutter. Mount the No.140 or 140-8straight cutter to the router.



8-30Place the router on the finger assembly andadjust the router until the cutter tip is levelwith the centre of the pencil line. Check tomake sure the cutter rotates freely.

8-31Rout out the waste between the pins. Checkto make sure no parts have been missed.(See page 141 for hints and tips on how tominimize tearout.)Use only light side pressure on the guidefingers.

8-32Remove the test pin board from the jig andtest it for fit in one of the tail boards.

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8-33Make sure the outside faces o face outwardon both pieces. The joint will probably betoo tight. A firm push fit is perfect, perhapsa tap with the heel of your hand. But hav-ing to use a mallet means the joint is tootight to take glue.

8-34If it is much too tight, move the fingerassembly in (away from you) by one divi-sion on the scale. If it is only a little tight,adjust the scale by only half a division.

8-35Replace the same pin board back in the jig,carefully aligned against the same side stop.Rout off the sides of the pins and test itagain for fit.

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8-36Test and repeat as required to achieve thedesired fit. Note: if you overdo it and make a loose joint,you need to move the finger assembly towardyou by the same amount as the gap at the bot-tom of the pins ➀ (when the pins are pulledagainst the socket sides). Test again on theother end of this (fifth) board.

8-37Once the correct fit is achieved, mark thefinal dTD PINS scale setting on one ofthe scale prints on page 67 for future ref-erence. Very slight variations to the scalesetting may be necessary with differentwood species or hardness.

8-38Rout all four ends of the pin boards, keep-ing the outside face o outwards. (Withluck you may not have used the fifth board.)

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8-39Assemble the box, making sure the tailboards face the proper way, inside faces in.

8-40The box should be square and in plane. Ifit is not in plane (i.e., the side edges of eachboard are not in line), then either the endsof the boards are not square or the boardsare not of equal widths.

8-41To form angled dovetails, refer to the Tips& Techniques bulletin “How to Rout AngledThrough Dovetails on your Leigh Jig”, sup-plied with the jig. The Leigh wrench mayhelp in this procedure. Attach it to the cap-tive nut in the front extrusion using the hexbolt and washer provided.




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D4Ch08 - Leigh Dovetail Jigs and Mortise Tenon Jigs | D4R Pro … · 2018. 6. 21. · Title:...

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