advice on Leigh jig use

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.

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

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.

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

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.

Attachment 497486Attachment 497487

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.

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.

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.

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/

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?

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

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...

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.

Quote:

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Originally Posted by 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.

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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.

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.

VRS is definitely worth it, if nothing more than more surface area for the router base to ride on.

I also find it easy to use, but before I had a digital depth gauge, I kept two routers dedicated to using it with 3/4" material. Actually, I still have those 690's dedicated to that, but don't mind resetting things with the digital depth gauge to get things back to being dead on first shot.

There is no skipping steps. Boards have to be milled perfectly.

One thing that caused me an issue is the tightness of the fingers. Called tech support and was given this advice. When tightening the fingers, push down on them with one finger and use three fingers on the other hand to lightly tighten the screw. Any more pressure will distort the fingers. Also, I bought my jig second hand as well. They looked fine, but a new set of fingers made my joints much tighter. I used a plain guide bushing, but had to buy a better router base.

After all of this, perfect dovetails!

Dan

Though I've seen mentioned watching the videos, how many actually have them and watch them? I have a Leigh D4, and when I bought it, it came with a VHS tape which wasn't the 'easiest' to watch. I found that the same videos were available on DVD so I purchased one. Being I don't use the jig but a few times a year, I watch the videos of what I want to do prior to setting up for the joint. If you have a computer set up to watch dvd's, you can even consider taking it into the shop while doing your setups to confirm what you're doing.
Just a thought.

I suggest calling Leigh. They are very helpful and very much want you to succeed. I had issues with my D4R Pro, called and sent many pics back and forth, until my issues were solved. As others have advised, starting with a flat and square workpiece is essential. After that, keep the router orientation the same with every pass. Many use 2 routers to keep from having variances when switching bits. Even at that, calling them is essential. They'll zero in on the issue just by seeing the joint you get.

This post made me dig out the Leigh D4 and give it another try. I bought some poplar this week and will set it up with a pair of DeWalt routers I purchased this month.

The OP's photo shows some really goofy dovetails, one in the center fits perfect, and the ones to the outside have huge gaps. It almost looks like the stock was not registered correctly against the stops or the router bits were not centered.

Te only helpful tips I can offer that I haven't seen posted is make a mark on your router and keep that mark always facing exactly the same direction. Others have said about not rotating the router and my Bosch router has a triangle shape mark in the aluminum but making it stand out makes it easier to see (and not rotate). Secondly made a second pass and be sure to make sure you hold the router tight to the jig's fingers. You shouldn't hear any wood being removed by the bit. If you do then your last pass didn't remove everything it should have. When new I would make 3 or 4 passes before I was confident I got it all. Once I got a feel for it I only do one extra pass just to be sure.

After two years with the device and two other WW trying trying it out I gave it away.

Have a D3 that i bought used. VERY HAPPY with it. have cut up to 24" dovetails on it. keep two PC 690's set up for it. Use only straight bushings and definitely use the factory dust collection. Have cut dovetails on boards 65" long with it.
NEED to always hold the router in the same position as you cut the dovetails.
Good luck
Ron

I have the D4R and cut a lot of dovetails and finger joints. Sometimes it takes awhile to get thing correct but not too bad for me.

I think the manual and videos online are really good.

Quote:

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Originally Posted by Holmes Anderson

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.

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i recently was given an old Leigh D1258R that had spent a year under a deck. After seeing how much they get for the new ones, I decided to clean it up and in the process of ordering some parts, also ordered the upgrade kit. After testing it out a little I decided to also order the VRS today. Yes, it’s wicked expensive, but by all accounts it works great. I doesn’t hurt so much when a product actually lives up to expectations. I hope so anyway. 😊

One thing that helps me is I put adhesive backed sandpaper on the clamp bars. This helps to prevent your pieces from moving.

Hi Alexandra,

Have you had any success with your dovetail jig?
I just purchased the Leigh Super 12 jig and it is a real learning experience.
any tips and or tricks you could provide?

Aaron