Leigh D4 Dovetail Jig

CONGER -The Irish diaspora in Munich: My first comments are that :

The router guide bush needs to be centered with a mandrel – not really described in the manual.
The mounting arrangement for the router guide bush in the base plate makes it difficult to stabilize the router in use… a potential user hazard.

I have now used the jig for two ‘projects’ (a chest for the jig using 18mm ‘solid’ maple sheet, and a table skirt using Tasmanian myrtle) and have some more to add. The chest walls were quite large (I dovetailed top and bottom in one piece), and so it was not easy to position them accurately in the jig… I had to get help, and even then it was not really satisfactory. The DTs were medium quality... some breakout... maybe due to the wood.

The table skirt was easier. The pieces could be placed securely and accurately. The cut was excellent. The DTs fit together with just hairline gaps. The wood was sized by handplane!

Concerning the jig, I must say that I am disappointed with the finish. I found out that the reason for my first debacles was a small piece of casting flash on the side stop bumpers. This meant that when the side stop bumper was tightened (using the setscrew) to the ‘side stop assembly’, the bumper moved! Not really a good thing for a "fine adjuster"!!

A similar problem exists with the jig fingers; the casting finish leaves a nasty unevenness (flash from the casting process) on the finger surfaces, such that the router does not ‘glide’ over the fingers… it has to be moved from ‘bump’ to ‘bump’… and lifted over each ‘bump’ to get by…. another source of inaccuracy. I tried Vaseline and ‘easing’ the edge of the router base plate. This brought little improvement. The entire finger assembly will have to be leveled correctly. Perhaps it will be sufficient to rub the fingers with a fine sandpaper. LEIGH should finish their castings correctly, and remove the flash from the casting process properly. What a stupid source of dissatisfaction in such an expensive tool!

I addressed the router base plate instability and the manual improvement (use mandrel for collar centering) to LEIGH support. They admitted that the instability could be solved by a better base plate; they are "not in the base plate business". They did not react to my suggestion that the operator hazard should be mentioned explicitly in the manual; it is currently covered by ‘DO NOT TILT THE ROUTER ON THE JIG’, and ‘KEEP THE ROUTER FLAT ON THE JIG ASSEMBLY’. The centering issue is vaguely mentioned in the manual… it could be pointed out clearly that better results are achieved using a mandrel… and perhaps LEIGH could offer a suitable mandrel as an option.

To summarize:

Not a ‘fussy’ jig to set up and use, as many have suggested… mostly due to the mostly excellent manual.
Dovetails of a quality that reflects the jig price could be achieved with a little effort and attention by LEIGH.
The hazard reference (tilting) must be covered better in the manual.
LEIGH could put some effort into an alternative router base plate / guide bush solution, and achieve a much better and SAFER jig.

Mike from American Sycamore: I teach beginners how to use the Leigh Jig, some with no router experience at all. I find the jig to be very user friendly after the initial set-up. We have a saying here in Indiana...some people would complain if you hung them with a new rope!! I have used the Leigh Jig for years, the school owns 6 and I have sold 100's....One should know that templates must be centered to work properly, this is basic to routing technique...and as for the "rough" edges I have never had that problem....the Leigh salesman at the shows does recommend a fine sanding of the jig and to wax the jig so your router will slide....and the rest is just operator technique and should not be blamed on the jig. If you have any problems Leigh is there to help in any way and I would also be glad to help if you have any technique questions.

Bob Lemon: A friend of mine brought over his Leigh D4 jig yesterday with the finger joint template on it. He hasn't been able to get it to work so the 2 cut boards come together properly. I, too, noticed the rough finish to the castings. If the customer is expected to do the final machining, then why doesn't Leigh include the files with the Leigh jig? One thing I found was the dial knob (part 3151) was a raw casting and the pin would not drop into the template support bar. It would drop in just far enough to hold it in place, but the cam on the bottom could not engage. It took quite a bit of careful machining with a file to get it to bottom out on the bar. My friend left the jig and his router with me to try it out. (I’d never used a Leigh jig!) When we figure it out, he wants lessons.

Mike from American Sycamore: I am so sorry that you are having so much trouble, but in my experience with hundreds of the Leigh jigs we have had no problems. As to "sanding" and fine tuning the jig, it is just tricks of the trade, same as waxing a jointer and planer bed. I use 600 grit sand paper and lightly sand the top of the jig just to make my router slide across easily. I also suggest that you wax the bottom of your router and the top of the jig. I have never had to do any "heavy filing".

As far as the router tilting, that is just user technique and will improve with more experience and practice on the jig. I do not mean to sound so harsh or insistent, but I have sold and worked with Leigh Industries for years, and find them to be of utmost quality and fair business practice. Leigh has nothing to do with router design and must work with what is out there.

Perhaps you should try another router manufacturer and see if its design is better for you to control. If you still have trouble and you are not happy, call Matthew or Ken Grizzley at Leigh and ask them for help. I am confident that they can and will be most willing. If I can help in any way, please give me an e-mail and let me know, I will try my best. One thing that helps me is I have several samples made up with the instructions written on them for quick reference. Sometimes it will be months before I use the jig again and the samples are a blessing. You see I suffer from CRS.

John Weber: I did some work on eight small dovetail boxes I'm building for some friends. Cut all the dovetails with the Leigh Jig. I've used the jig for a number of small jobs, but this was the first multiple unit very small production run. I thought I would pass along some of my thoughts:

Two routers don't really buy you much, I went ahead and set up both routers thinking I might need to go back and touch something up - I did not and checking and double checking for center is an extra step not needed when using one router.
Brass bushings seem to do better that the steel Leigh bushings. I used a Leigh bushing and a brass (generic) bushing. The brass seemed to slide and follow the jig fingers easier.
Be careful when centering the bit in the bushing. If you hold the router the same way each time your joints should fit fine regardless, but having the bit as close to center as possible makes everything better. My Porter Cable routers seem prone to off center out of the box. By rotating the sub-base I was able to get the guide bushing reasonably centered. If you have not used your router with guide bushing before, you might want to double check, as it doesn't make a difference for most normal operations.
8mm bits are "THE WAY TO GO"! I only could use the straight 8mm bit, but it seemed to do remarkably better with less chatter.
Backer blocks help a bunch! In addition to the normal rear block, a side piece mounted next to the work piece really helped with blowout.
Technique is everything! By the end of each stack, my dovetails had improved a fair bit - from some slight tear out to almost no tear out.
Smooth action, don't rush and they did great. I was using walnut that seemed to machine well, one or two boards were a bit stringy.

I think I like my regular 690 over the D-handle base. I've always used my d-handle with the jig, but after using my regular base 690 it seemed to work better. I was cutting dovetails in thin material so you space the work out and it there isn't as much of the jig hanging over. The d-handle base seemed to add weight off the jig causing a greater tendency to tip. The regular base seemed to keep my hands and weight over the jig for better support.

I like the jig high. My jig is mounted to a box that is secured to the workbench with the vice a bench dog. I'm not sure the height, but the box is about 7" putting the jig around 40" (I think). If you really want to know I can measure it later. I initially had the jig mounted on a board like in the manual, but the extra height is great and I like the storage too.

Full-length stop block. When using thin stock, you use a spacer with a full-length stop. I think I prefer this to the two-point stop on the jig. Full length just seemed easier to mount and you could quickly notice if you were not square.

Has anyone polished the jig fingers with a buffer? I thought I read it somewhere, but never did it. Anyone do it - any difference? Wax seems to really help as well.

I'm sure most of this is old hat for most of you, but for some of the more novice users a few ideas might come in handy.

Art Liebeskind: Sorry guys, my only complaint is that If I go to lunch in the middle of a job, I need to be retrained again afterwards. Seriously, other than a rehearsal each time I use it, I really like the Leigh Jig and am positive that their customer service will walk you through any problem. Just my two pfennigs.