|Project by RobH||posted 02-05-2008 06:09 AM||5164 views||4 times favorited||4 comments|
I promised a posting on the jig that I built to rout the dovetail mortises in the bottom of the 2×4 Shaker table. Well, here I go. At least I am going to try to explain it. The picture in the project pictures is the overall picture of the jig. Basically, the leg is put into the jig with the bottom side on the bolt side of the jig. The router is slid on the rails to cut the dovetails in the pedestal. I am sorry I do not have an actual pedestal to put in the jig right now. The block of wood spanning the top of the jig is a stop block that limits the travel of the router.
Let’s start by taking a closer look at the bolt end of the jig.
On this end of the jig, a hole is drilled to allow the 1/2” bolt to pass through the end wall of the jig. On the inside of the end wall, a hexagon is chiseled to hold a 1/2” nut. The hole for the bolt should be chiiseled to a hexagon to prevent the bolt from turning. So, first on the bolt is 1/2” nut. Then there is an aluminum plate with three holes drilled into it. One for the bolt, and two to hold the aluminum plate against the end wall. Next is a washer (note the holes filed out so the washer will clear the screw heads. If I had made the aluminum plate a little longer, this would not have been needed. Next is another nut. When all together, the two nuts are tightened against the aluminum plate to lock the bolt in place which in turn holds the pedestal in the jig. When this end assemble is put together, it looks like this:
Note in this picture that the bolt is sharpened to a point to go into the pedestal.
Now, let’s travel to the other end of the jig. Here is a picture of that end:
This end is basically a counter-bored hole that fits a brass bushing. The only real important thing here is that the hole in the busing is 1/2”.
When the pedestal is turned, a 1” diameter tenon is turned on the top that fits into the support disk that is underneath the table. This end of the jig holds that end of the pedestal. Not the line on the end of the jig is for lining up the hub that fits in the hole so that the legs will be spaced evenly at 120 degrees apart. The following is a couple of pictures of the hub.
The hub is a turned piece made to hold the pedestal top. The first picture shows the 1/2” tenon that was made to fit into the busing in the end wall of the jig. The second picture shows the 1” hole that was bored into the hub at the drill press. This hole holds the 1” tenon on the end of the pedestal. The main part of the hub is 1-1/4” in diameter. The next one will be at least 2” to make things easier. The screw in the end of the hub in the second picture goes into the tenon on the top side of the pedestal to keep the pedestal from turning in the hub. Notice the lines on the main part of the hub. These are 120 degrees apart, the spacing of the legs.
The other side of the busing end wall has a screw that goes into the hub to keep it from turning while the dovetail slot is being routed. This is shown in the next picture.
Thus, the screw in the hub keeps the pedestal from turning in the hub, and the screw in the end wall keeps the entire pedestal from turning while you are routing the dovetail slots.
The next picture shows the hub placed in the end bushing by itself for a little better idea of how things sit. Notice the reference line on the hub lined up with the reference line on the end wall of the jig.
So, the basic operation of the jig is as follows: (1) Attach the hub to the 1” tenon on the top of the pedestal and lock the hub to the pedestal with the screw. (2) Insert the 1/2” tenon on the other end of the hub into the bushing and tighten up the bolt on the other end of the jig to hold the pedestal. (3) Run the exposed nut on the other end of the jig down to the metal plate and lock it in with a little pressure from a wrench. (4) Turn the pedestal to align one of the lines on the hub with the line on the top end-wall of the jig. (5) Lock down the rotation of the hub by inserting the screw from the outside of the jig end-wall into the hub. (6) Set the stop block for the length of slot that you want. (7) Do your routing on the pedestal. (8) Unlock the rotation of the pedestal and rotate the pedestal until the next line on the hub line up with the line on the end wall. (9) Go to step seven and continue until all the routing is done.
Note that it is very important that the center of the bushing is lined up with the sharpened end of the bolt.
I hope this has been a good explanation. This is probably something that would be better done with video, but I do not have time for that right now.
If you have any questions, please let me know and I will do my best to answer them.
-- -- Rob Hix, King George, VA