Lynns Box Joint Jig

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Lynns Box Joint JigPost by arcticfox46 on Jan 24, 2010, 3:47pm

Lynns Box Joint Jig

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I don’t really know who Lynn is or the real source of the origin of this design. I do know that it has gone through a couple ofdesign iterations – including some my own. I will not take credit for the design. I am however, documenting a more detailedinstruction on how to make it – from start – to finished jig. I will also include instructions on how to use it.

I will eventually create a model in Solidworks and make detailed drawings of every part, including the parts I added. I will alsobuild a full BOM (Bill of Materials.

Here are some reference links to the web sites I used for the basic information:

http://www.leestyron.com/lynnjig.phphttp://www.leestyron.com/lynnsjig.pdfhttp://www.leestyron.com/images/LJ1.swfhttp://www.leestyron.com/newlynnjig.php

It’s a little difficult to sort out just exactly what is going on in those places – but I will put it all together into ONE tutorialhere.

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Lynns Box Joint Jig http://worldofwood.proboards.com/index.cgi?board=genwork&action=pr...

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Cut out all parts per drawing in one of the links above.


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Mark and cut slots in slide sidesMark hole locations and drill (4) 7/16 holes (for tee nuts)

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Drill (3/16) and counter sink (6) not 4 as pictured holes in slide assembly. The two additional holes go in line with the 7/16hole. See pic-6

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Glue and screw (1-5/ 8 decking screws) slide assembly back sides and front together. Make sure everything is held in square.


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Sand all the joints flush (optional – cosmetic). Notice the additional (2) 3/16 counter sunk holes in sides.

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Mark sides on inside with an alignment line 2” in from back, draw line square. This is for alignment of the slide rail.


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Glue and screw sides to slide. Make sure everything remains square,Glue and screw – front and back to sides


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Sand all joints flush – clean up all excess glue. (optional-cosmetic)

Pic-10Glue and brad nail bottom to upper assembly using 1” brad or finish nails. Do not nail within 1” of middle. That is where thesaw blade will be cutting.


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Hammer tabbed tee nut into hole in side assembly on left side of jig.


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Cut 3/8-16 threaded rod to 33” long

Grind both ends of rod constantly turning the rod while grinding, like sharpening a pencil. One position, perpendicular to thewheel – then at about 30 to 45 degrees to the wheel. Wheel rotation going from the outside of the rod towards the center ofthe rod. That pushes any burs away from the thread. Finish on the bench with a very fine file. Again file from the outside ofthe rod towards the center. You will end up with burr free threads and the nuts will fit easily.


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On one end place a fender washer – nut – flat washer – nut, in that order. Lock the nuts together at the very end of the rod.The fender washer will remain loose.


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The reason for the washer is to act as a support for the nut driver. The socket will stay engaged on the one nut and not getstuck on the jam nut.

This will be very helpful in driving the rod. Remember the 16 pitch means it takes 1 full revolution to advance the rod 1/16 inch– or – 16 turns to advance 1 full inch. You’re going to be advancing around 25-30 inches. I little help will be needed,

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Once the rod is through – you need to hand screw the tee nut with no tabs onto the rod until it bottoms out.

The threaded rod should turn freely. If it is bound and does not turn freely – unscrew the tabless nut a little so that the rodturns freely. Then screw in ONE small screw into one hole in the tee nut.. Do NOT tighten the screw or the threads will bind.The screw the only to hold the tee nut from turning.


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The screw the only to hold the tee nut from turning.

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Cut a 1-1/2” x 4” piece for the handle. Use a fender washer to tract out the curves for the ends. I sanded the ends in a fewminutes on a HF disk sander.

Drill 7/16 hold on one end and a 3/16 hole with countersink at the other end.Of course sand it.

Cut a dowel 1-1/4 Diameter 4” long

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I predrilled a 7/64 hole into the dowel centered.


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Assemble the crank and handle with glue and a 2” screw. Do not pay attention the fence slide attachment in the picture – Idecided to not use it and removed it.

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Drive the rod is driven all the way through. Now install a fender washer and two nuts. Adjust side to side play then jam nutstogether.

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Now put the handle on as shown.Nut – plain washer – fender washer – handle – fender washer –plain washer – nutTighten loosely together – we will be coming back to this later,

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I decided to attach the unit two niter gages – and not to the fence like the instructions refer to.

The center of the jig should be over the center of the blade – then secure the jig to the two miter gauges.

Make a cut in the center in the jig.

Set the edge of the slide to the edge of the blade.

Now adjust handle so that it hangs is straight down,


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Whew -- That’s all for today’s show.


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Lynns Box Joint Jig