Questions for Leigh D/T Jig Experts

[Larry Prince]

I'm no stranger to this jig and have had good results with it in the past, but it seems the more time I spend with it the worse my joints get, so here's the particulars:

I'm using a pair of Triton 2-1/4HP routers, with see-thru bases by Pat Warner, and the bases are drilled to accept the brass PC type guide bushings sold by Leigh. (More specifically, they were CNC-cut by Pat).

To describe the problem, picture an assembled joint, looking at it towards the tails board. The first tail fits tight on its left edge but has a large gap on its right edge. The second tail fits tight. The third tail has large gaps on both its edges. The 4th tail has a large gap on its left edge and fits tightly on it's right.

Read first to fourth from left to right.

The material being cut is 5/8" poplar.

I really dont think it's the jig itself, but rather something to do with the routers, and something is moving when it shouldn't. I've double checked that the guide bush is tight in the base, and the base is tight to the router. The guide bush is as centered on the bit as I can make it by eye.

So the questions are: Do any of you have a clue as to what might be happening here? What Should I be looking for? What can I do to make sure the pins/tails all come out to the proper size and spacing?

At the moment I'm completly stumped since I've had good luck in the past and I'm always meticulous with the setups. Any advice will be greatly appreciated.

[Michael Koch]

I have the d4 jig and have not had that problem. Maybe you should start from scratch on your setup and see if your settings are correct. I know that everytime that I pull the jig out, I need to spend time witht the manual to get things right. MK

[James Biddle]

Are you keeping the router in the same orientation on the jig to compensate for any concentricity problems? Also, did you set the template guide using a centering cone? What router/template guide/adapter setup are you running?

[Gordon Peery]

I've just finished a 2 week session with my D4 & 11/16" cherry, maple, walnut, white oak, and mahogany. Most of my joints do not allow a piece of paper. BUT, early on I had some gaps as you described. I discovered "stock creep" - wood not firmly clamped in the jig.

Other posts have mentioned guidebush/bit lack of concentricity (sp). I can see that problem in some of my PC 690 rigs. Carefully resist any router body rotation or change in orientation as you cut. Another difficulty I had until adding a Jet 10-20 Drum Sander was stock thickness variation. I now go: resaw, jointer, thickness planer, drum sander (very light), and ROS (very, very light). Hence, now stock thickness less than 1/64th +- .......and without any jointer or planer tearout.

Previously, I would make a very tight "test joint" and then go through my list of woods, cutting all the joints, without adjusting router depth or jig settings to accommodate for the changing stock thickness . Some loose joints resulted. Now, very accurate stock shickness equals very tight joints.

One last point: The black phenolic PC 690 bases were not perfectly flat. I could feel some slight tipping as I moved the routers across the jig fingers. I taped a 120 grit sheet on my TS and finished with 400 wet-or-dry to flatten the bases.
Then a coat of..... Oh, by the way. I see folks use the word "Wax": That sounds so "Horsehide Glue" like, - like yester-century! For all your cast iron tool surfaces....... for that matter all surfaces, blades, cutters, try some Sail Kote (also "Team McLube" - from West Marine or McGee Industries Aston, PA). Two very light dustings (spray can) dries in 5 seconds; the slipperiest thing on planet earth, without wax-gunk buildup . In fact, it reduces drag to such an extent that pushing a board through the jointer or shaper feels dangerous because there is no feel of back pressure. TPFE Dry Lubricant technology - So amazing, I wouldn't even think of trying another brand. I have no connection with West or McGee. Gordon

[Charles Lent]

Concentricity of your router guides and/or variations in board thickness can cause this. Either get your guide bushings concentric to your routers or be very careful to hold the routers in the same orientation when you make the cuts. I have placed a mark on one side of the base of all of my routers and always point this mark toward the direction of cut to eliminate any chance of concentricity affecting my dovetail cuts. Also, make very sure that you are dropping the guide fingers down flat to your boards each time. If the boards are narrow and the jig is wide you may be dropping the guide's unused end too far, causing a bow in the guide, which will lift the guide slightly off of part of the board. The fingers must always be flat against the board when you cut the dovetails. If you have this problem you can position another board in the far end of the jig for the finger guide to rest on.

Charley

[Larry Prince]

Thanks guys for all the suggestions. For starters I'm going to get new guide bushings and a centering tool, and once i know the bits are centered I can start looking at some of the other things that were mentioned.

(Sorry for the delay in response but work does tend to call sometimes):)