Horizontal Router Mortiser
In one way or the other I was never satisfied with the ways I had used to make mortise and tenon joints. Then I saw a horizontal mortiser and it appeared to address every shortcoming of the prior ways I had used. Later I saw the JDS MultiRouter, which is an engineering marvel but the price was out of my reach. Still, I really liked the concept of that machine and thought about how I could make something similar and simpler. The more I considered it, I realized that I only needed motion in the X-Y planes, since I normally use loose tenons. That simplified the design substantially. So I set out to design a machine that would be easy to set up, easy to use, have high accuracy and repeatability, and that would be easy to build and modify using inexpensive, readily available materials. The result is the machine shown below. It has exceeded my initial expectations and I have found many uses for it beyond making simple mortises. It does make mortises quickly and accurately, but it will also make integral tenons, dowel holes, sliding dovetails, and raised panels and other molded parts.
Horizontal Router Mortiser - Feb. 2015.wmvThis link will take you to a slide show showing the basics of how the machine works: direct link.
Click on the second photo to view a video of about 15 minutes I made showing the basic setup and operation of the machine. If it won't open copy this URL to a new tab: https://1drv.ms/v/s!AptW3HZ8tqg0g4EO2HyqfthUYuLVYQ
A SketchUp drawing of the machine with most of the details is attached below. You may download it for free. Click on the downward pointing arrow near the right margin to download the model. (Since I moved to the new Google Website this feature no longer works. Send me an email if you would like the SketchUp file and I will be happy to send it to you. )
Building the machine is straight forward as long as you can cut square parts in 3 dimensions. Most major components can be cut from 2 sheets of 3/4" MDF, 2 x 4 feet. The hardware consists of 1/4" carriage bolts, 1/4" toilet bolts, a few 1/4" knobs and wing nuts, a short length of 3/8" x 16 tpi threaded rod and two nuts, and three hold down clamps. I built the machine for about $50 out of pocket, since I already had the hold down clamps and a router.
It is critical that the dados be perfectly parallel and that they be exact mirror images on mating parts. To do that I referenced both cuts from a common edge, and made both cuts in mating parts before moving the fence to make the second set of cuts. I assembled the machine with the intention of future modifications; therefore, only the sub-assemblies are glued. The maple runners are pin nailed in place so they can easily be removed if required or desired. The risers and backrest are attached only with screws, for the same reason.
If you would like to use my machine as inspiration to build your own I will be happy to answer any questions you may have before, during, or after the process. In the end, however, you assume all responsibility for your own safety both building and using it.