"I was recently commissioned to build some entry doors in the same style of a set I had previously built for a different client. The original doors' joinery was traditional mortise and tenon. The mortises were cut using a large plunge router, edge guide, and a jig that trapped the edge guide's fence. The tenons were cut on the router table. While the outcome was acceptable I wanted a simpler set up this time around. I also had more than double the number of doors to build and in a small shop simplifying things is about all you can do to stay efficient.
I have a Festool Domino machine and feel that the M&T joints created with the Domino would have been strong enough for this application, yet I wanted to give it a try with the OF1400 and OF-FH (now called "Plexiglas template").
The OF-FH template attaches to the base of the OF1400 with 2 provided screws through pre-drilled holes. There is a small amount (less than 1mm) of play in the mounting holes and a centering mandrel would be a quick way to ensure the router is mounted perfectly centered on the template.
It is not necessary for the router to be perfectly centered on the template to have perfectly matching mortises. You just have to be concious about the orientation of the template to each work piece. Somewhat like using the domino fence to register off the face of each piece, you have one leg of the template reference off the same face of each piece. I used blue tape on the refence leg of the template and placed bits of blue tape on the reference side of each piece getting mortised to keep everything simple. Centering the template on the workpiece is a matter of adjusting the legs to be snug to the workpiece and read the same on the centering scales on each end of the template. There are also etched center lines that can be adjusted to a pencil line if offset mortises are needed.
I made some plywood gauges to mark the start and endpoints of the mortises. Make sure to use the appropriate colored sharpie. It is green if you can't tell.
I am using a 2-1/2" long, 1/2" diameter mortising bit. I align the edge of the bit with the end of the mortise and plunge to full depth. In this case the depth is 50mm or just under 2". I repeat that at the other end of the mortise. There is now a 1/2" x 2" deep hole at each end of the mortise.
The mortise can now be completed with a series of 1/4" to 3/8" passes connecting the holes. When nearing the full depth of the view of the mortise is blocked by the router and I rely on my hearing to tell when I have reached the hole. When the bit reaches the hole the pitch of the router increases due to the lessened load on the bit. I slow the progression a bit and stop when I hear the bit engage the end of the mortise.
The best part of this method is that once the router and template is set up the same procedure is used for all the pieces. All the rail mortises are cut then all the stile mortises are cut using the same set up.
Once all the mortises are cut, I mill the tenons. I have used up a bit of scrap mahogany and thickness them for a slip fit with a little play along the length and no play in the width. It is not necessary to have a matching round over on the tenons. I have just chamfered the edge on the jointer prior to cutting them to length.
The test fit (shown above) resulted in excellent alignment of the parts. The creation of mortises for slip tenon joinery made easy by using the Festool OF1400 and OF-FH Plexiglas template."
Thanks, Eiji. Now that's working Faster, Easier, Smarter.