advice on Leigh jig use

[Alexandra van Geel]

Hi all. I recently bought a secondhand D4 jig and have been trying to learn the ropes. I'm not too happy with how this trial cut has turned out, and I'm not sure what I'm doing wrong. As shown in the attached photo, I have some pretty significant-- and uneven--gaps from pin to pin. The middle pin is a reasonably snug fit, although not perfect, but the ones to each side have unacceptable gaps.

I might guess that this is because I moved the finger assembly too far in when cutting the pins, but I worked up to that setting very carefully, and the joint would not go together when the finger assembly was further out-- presumably because the fit on the middle pin was too tight and prevented it.


Anyway, I'm not sure what I'm doing wrong here and was hoping someone experienced with this jig could advise.

[Jacques Gagnon]

Alexandra,

You are not alone in your quest to master dovetail jigs. I have not worked with the Leigh product; my experience with a Porter Cable model has allowed me develop patience and perseverance 😱.

I am sure somebody who knows Leigh products will soon provide you with some feedback.

Regards,

Jacques

[Richard Coers]

The only dovetail jig that is easy to setup is a Keller. Its second advantage is the thickness of the wood has no effect on the fit. Set the comb one time to match the bit. The only adjustment after that is for the thickness of the wood to set the height of the bit. The pin and tail fit is never changed with that movement, and the only time you have to check for pin and tail fit ever again is when you buy a new set of bits. Keller is a dream to use. You can adjust other jigs for a half day, and if your wood is not impeccably prepared to the same thickness, the fit changes. Even a few thousandths say from snipe on the board, and the fit changes. The main reason I bought a Performax sander is to get better dovetails off my Omni-Jig.

[Christopher Herzog]

I would offer to check the manual on a backing you can make for the left side to help line up and clamp against. Another thought is to adjust the bushing to tighten the gaps. It takes some practice pieces for sure and is a router bit collection to use on different thicknesses.

Good luck with it!
Chris

[glenn bradley]

Hmm, I may be the odd man out here but I find the Leigh jig to be nearly fool proof. The result you are showing makes me immediately question the stock preparation. I don't mean this in an accusing way. I am just saying that the stock must be face jointed, edge jointed, planed to thickness, and ripped to width so that all faces are perpendicular or odd things will happen.

If the fingers are spaced per the instructions and the pieces being machined are placed and rotated per the instructions you will get a good result. I do not know anything that the jig can do that would yield the irregular results you show. Improper placement, spoil in between blanks and the jig or some other irregularity would be required. I know it doesn't help to have someone tell you they are not having your problem but, I am hopeless on hand cut dovetails but have good results with the Leigh.

Jewelry Boxes 20220423 (101).jpgJewelry Boxes 20220423 (106).jpg

[Jim Becker]

Be sure you are using a centering jig when you install your guide bushing and router base...and...keep holding the router in the exact same orientation as you move across the workpiece and cut. Do not rotate it. Why? Small deviations in in "centering" can cause small spacing differences if you rotate the machine.

[Thomas McCurnin]

I have both Leigh Jigs, and sadly was in the same boat as the OP. One has to watch the video, set up the jigs carefully, watch it again to do test cuts, and then make adjustments. The learning curve is steep and at least for me took nearly a full day just to watch the videos repeatedly, do the set it and do the test cuts.

Fast forward--my Leigh Jigs sit in a box with a bunch of other tools that I bought and never used. Honestly, I can cut a hand cut dovetail faster than setting up the Leigh Jig. Perhaps if I was making a production run of drawers, the learning curve would be worth it.

The Keller Jig, in contrast, worked perfectly out of the box. Granted it is not as adjustable, but at least it works.

By the way, Jim is correct about centering the router bit, which is a known problem with the Leigh Jig, since it rides in guide bushings. The Keller Jig uses pattern router bits, and centering the guide bushing and router bit are a non-issue in the Keller system. But without watching you set up the Leigh Jig and re-watching the video a few more times, I can't diagnose your joint problem.

[Ken Krawford]

Jim beat me to it. Be sure the bushing is centered and don't rotate the router - ie keep the 12 o'clock position the same.

[Rich Markiewicz]

Hi Alexandra - Not sure if you have a D4 or D4R. As others have mentioned, there is a definite learning curve. Read and understand the manual, watch the videos, plenty of test cuts, etc.
As Jim mentioned, the guide bush & router orientation is fairly critical to the operation. The D4R-Pro has an elliptical guidebush (E-bush) to allow adjustments. In reading through the D4 manual, they only seem to reference straight guidebushes and adapters. You may wish to call them and make sure you have all the parts shipped with the original. As Glenn stated, stock prep is important. I have gotten good results w D4R-Pro, but it has taken some dedicated time and practice. Good luck w the process.... -Rich M.


https://www.leightools.com/d4-user-guide/
https://www.leightools.com/d4r-pro-user-guide/

[Jeff Ramsey]

I’ve a D4R Pro and the dovetails are consistent and tight; so tight that I don’t test fit (a little glue and final assembly is it). I had a Keller and sold it; the Leigh is more flexible. Are you certain your router bearing and collet are sound and the bit isn’t wobbling?

[Alexandra van Geel]

Chris - can you explain what you mean by "adjust the bushing"? I'm not sure I follow what you mean by that. Thanks.

[Alexandra van Geel]

Thanks to all. The jig is a D4, not the D4R-Pro. I've definitely been scouring the manual . The bushing and bits are brand new, and I've been careful about stock preparation. The point about centering and keeping the router in a constant orientation are points I had not considered, so I will give that a go on the next test cuts. Thank you to all who responded!! I will keep an eye out on this thread in case there are other things I should also try...

[Jim Becker]

Alexandra, you can buy an actual centering jig to get the router base (and hence, the guide bushing) concentric. They insert in the chuck like a router bit would and look like a cone. Not real expensive and an essential setup tool for anyone using a router with guide bushings, not just for dovetail jigs.

[Edward Weber]

Chris - can you explain what you mean by "adjust the bushing"? I'm not sure I follow what you mean by that. Thanks.

Leigh guide bushings are often an e-bushing.
They are not round but elliptical with numbers ranging from 0-10.
Depending on the orientation of the bushing (where it's set) the fit of the joint will either be tight or loose. This is why it's essential to keep the router at the same orientation through the cuts and start with the same bushing setting for pins and tails
If you start straight and slightly rotate during the cut, it changes what part of the bushing you're riding on and will change the width of the cut, either tighter or looser.

[Holmes Anderson]

Lots of good advice in this thread. I use an older D4R like yours. The e-bush is not for these older models. Based on that single photo I would say that one of the boards was not properly registered against the jig when clamped or may have moved while being machined because the pins and tails are offset along the width of the boards. Alternatively, the fingerboard may not have been flat against the board. The left edge of the board must be square to the jig and the fingerboard must lay flat on the edge of the board. Obviously, the clamps must prevent the board from moving while being machined. It also looks like the fingerboard was set too far towards the back of the jig. That's why the pin sockets are too wide. The depth of cut is also too deep. That is why the pins don't bottom out in the pin sockets. If the pins are proud of the tails then that is also a depth of cut issue (too deep). It is easier to set the depth of cut accurately with a marking gauge than a pencil. The differing gaps might be due to the boards being cupped. Until you are more comfortable with the jig it might be a good idea to sneak up on the best settings. Another thing to be careful about is that both ends of the fingerboard are at the same setting. There are multiple marks on the jig and finding the right one can be tricky if your eyes are old like mine and there is sawdust in the way.

Related to the D4R, has anyone bought the upgrade kit for box joints and single-pass half-blind? Worth it? How about the VRS? some dust collection and router support would be nice but the price is not so nice.