If you follow the blog, you will already know I tested the Leigh D4R Pro dovetail jig to make 3/8-inch finger joints. It worked beautifully, without the need for additional templates like the F3 finger joint template. Since the D4R also promises 3/4-inch finger joints without additional anything, I had to try it.
Note: Please click on any image to enlarge; once viewing an enlarged image, you can navigate through all the images using the arrows on the bottom-right hand corner of the images.
Following the 3/4-inch procedures included in the User Guide, I made the joint shown in the following photograph using thick quarter-sawn white oak 5-3/8″ wide boards (please refer to Chapter 15, “Box Joints”, starting on Page 53):
The use of very thick oak is as demanding a test for finger joints with good fit, as it is for dovetail joints. It is demanding because the wood cannot be compressed when assembling the joint by hand only; maybe a mallet will compress the wood sufficiently, at the risk of something failing from pounding together the joint.
What would happen if thinner boards were used, and the wood is walnut? This would mean slightly more compressibility of the wood; also, the joint should be a tad tighter, to account for the added compressibility. I adjusted the e7 e-Bush by 1 division to the “tighter” side; this translates to a tighter glue line fit of 4 thousands of an inch (0.004″ ). Using walnut boards 6-15/16 inches wide, the following photo shows the resulting finger joint:
On the first dry fit I was able to tell the joint was just a tiny bit tighter with the wider walnut boards, compared to the joint I made earlier with the white oak boards. However, by the second and third time testing the same joint, it seemed to be just perfect, as the walnut had compressed ever so slightly. For boards this wide, I was satisfied.
Most importantly, I made 3/4-inch finger joints on thick boards and on thin boards, using oak and also walnut boards.
Worth noting, #1: I also made 3/4-inch finger joints on narrow boards 2-9/32 inches wide, and on boards 3-27/32 inches wide. I had difficulty making 3/4-inch joints; I called Leigh Customer Support, and also sent e-mail messages with photos of the results I was getting. The long story made short: I was not placing the work piece perfectly vertical under the finger assembly. The “problem” is now solved! I am now very careful with placement of narrow boards under the guide finger assembly when making 3/4-inch finger joints. Why does this “problem” happen? Easy, once I understood what was going on. To make this large finger joint requires first routing all sockets and pins boards; a spacer is then placed against the integral stop on the jig body, and the pins and the sockets boards are routed a second time. ♦♦♦ With narrow boards it becomes very tricky to properly align the boards under the finger assembly, because several of the routed recesses fall directly under the surfaces of the guide fingers ♦♦♦ In other words, there is not sufficient surface area on the board registering properly under the finger assembly. Solution: Do whatever you must do, to properly align the work piece with the support board under the finger assembly.
The following photo shows this dilemma in detail (click to enlarge) – enlargement of single finger under one guide finger:
In reality, the board looks like this – it is the middle guide finger I showed in the photo above:
Worth noting, #2: Although I will (likely…maybe…) get rid of my old D4 dovetail jig, I will keep the F3 finger joint template. I will need it when I make finger joints different from 3/8″ and 3/4″.
My opinion on making finger joints on the D4R Pro dovetail jig:
Bottom line: The D4R Pro dovetail jig is a terrific jig to make finger joints in two sizes, 3/8″ and 3/4″; it makes these two sizes without the need for additional templates or gizmos. The use of the e7 e-Bush gives the user the capability to dial in the fit of the finger joints in 0.001″ increments; the full range of adjustment of glue line is a whopping 0.020″ — in practice, adjustment of only a couple of divisions is required on the e7 e-Bush (0.004″). If you have been wanting to get a top-of-the-line dovetail jig that also makes finger joints, your wishes are now reality.
Disclosure: Leigh Industries is a sponsor of this blog. I sometimes receive tools from my sponsors, for evaluation purposes. I also receive a small commission from your purchases through my Affiliates (Woodcraft, Woodworkers Book Shop,Amazon.com, Rockler, and StudioPress); these help defray my costs some. I thank you for your support!
Still-to-do: Single-pass half-blind dovetails with the D4R Pro. This is also a new feature of the D4R Pro. I will publish an article about it in the near future. If you would like to upgrade your D4R to the D4R Pro, visit this page — the page also shows upgrades to older jigs.
— Al Navas