Thanks to a couple of commenters, Stan and Johan, I can now add a little background information and a written reference to my record for this joint. The overwhelming evidence is that this joint has been historically employed primarily in applied moldings. Think paneled library, coffered ceilings and window mullions. A written reference to this joint can be found in “Woodwork Joints: How they are Set Out, How Made and Where Used. by William Fairham” on page 22, figures 49 and 50. Now that I have somewhat nailed down the historic use for this joint, let me address my earlier statement of strength.
In my first post on this joint I made a statement as to the strength of this joint. However, I failed to do so with any comparative or qualitative information. I have a tendency to be myopic in my woodworking. Focusing only on my unique applications and I apologize if my original statement caused confusion. I typically use stock that is 36mm(~1-1/2″) square in section. Mostly due to my attempt to use 2x construction lumber for my projects when possible. So my statement of strength is based upon this point of view. Therefore, when executed in 36mm(~1-1/2″) square stock, the thinnest section of material will still be a full 18mm(~3/4″) thick. Plenty of structural strength for most furniture applications. To further clarify, this joint is not stronger than other available options. So why bother? The joint does offer a couple of advantages.
The first advantage is the ability to have an overhang section, much like the top and bottom rails of my HB Tansus. This joint will allow the addition of mid-rails that mimic that look. The second advantage is the ability to chamfer the long edges before assembly.
To make this joint easier to execute with consistent results there are few items that can be employed. To consistently pare the miters a jig can prove indispensable. The jig can be made from just about any piece of scrap. I plan to keep this jig for a while so my wood of choice needed to be stable and I chose to use birch plywood (see Stan’s warning in the comments below about using plywood for this). I glued two 3/4″ pieces face to face to yield a 1-1/2″ thick section and screwed an additional piece of ply to the edge of this to create a fence. Note that the fence extends above and below. This will allow me to use the jig on miters that slope away or slope under. Depending on need. Then I cut a 45° angle on both ends. By making the jig double-ended, I can pare miters in either direction while referenced from the same face of a workpiece. I used a power miter saw to cut the 45° angles and it felt a little like cheating, but it’s very accurate. Just to be sure though, I checked the angle on each end and also verified that the ends were square to the fence. The last thing that you want is a jig that is inaccurate.
For chamfering the long edges a cradle or multiple cradles can make the task much easier. The cradle is just a simple “V” block. A single long cradle can be made to match your workpiece or you can create several smaller blocks that can be spread along workpieces of varying lengths. You can use your bench stop to work against or you can build in a stop into the single cradle or into one of the multiple cradles. The “V” cut should form a 90° angle. In use, the cradle simply holds the workpiece so that the edge being chamfered is presented uppermost. Don’t underestimate the utility of this simple work holding aid.
To further add accuracy and consistency a chamfering guide can be employed or you can utilize a specialty plane. I have a Japanese chamfering plane (mentori wanna) that I purchased almost a year ago but have never used before. It can be adjusted for width, the blade is skewed and the blade carrier can be moved side to side so that you can utilize the full width of the blade. This plane only does one thing, but it does it exceedingly well.
With all of the above in hand I had another go at this joint. I completed the layout and sawing just as I described in my first post. I want to emphasize the importance of making all of saw cuts to depth before removing any material. Once you start removing material, you start loosing layout lines. Leave the miters alone at this point though. With the saw cuts made, I removed the center section. Then I removed the waste from the sides. I was careful to leave my layout lines, save one. The depth of the lap I pared until I all but removed the layout line. Leaving just the faintest trace of the original line. In theory the two halves of the joint should meet at the middle of the depth line. By removing the bulk of the line, the joint should come together without bottoming out too early. Next I began work on the miters.
These are small miters. In a larger joint some of the miter waste could be removed with a saw. For my smaller work it was much easier to roughly pare away the bulk of the waste with a chisel. I then put my newly minted jig work. Working systematically, paring each miter. Checking for fit after each round. It took four rounds of paring before I achieved a fit that would allow the joint to be knocked together with a mallet. I have to say that the paring jig makes this joint much easier to execute accurately and resulted in a well fitted joint, IMHO.
I then knocked the joint apart and set my chamfer plane to the desired width. The workpiece was then mounted in the “V” blocks and a chamfer was planed on all of the long corners. The chamfer plane is a fun tool to use and is very accurate, but you can get by with just about any plane as long as your careful.
With the chamfers in place, I reassembled the joint. Not too shabby for try #6, if I do say so myself.
I hope that the above information adds a little clarity to the history and execution of this joint. I also hope that, like myself, you give some thought to using this joint in unconventional applications. At the very least, I hope that you make a few examples just for the fun of it.
Part 1 Greg Merritt