Sliding dovetails are one of the unsung joints that are seldom used in woodworking, too bad because they are not nearly as intimidating as they may seem and they hold fast and give lots of area for glue to grab on to making an excellent, tight joint.
In this video we are ultimately making a 3 legged pedestal table but in order to get to that point there are many steps and this is another one of those steps. We needed something to but the dovetail slots into so we needed to start off making a six sided or hexagon shaped column or post.
Using the correct technique on a table saw, a column like this can be cut accurately in a couple of minutes. The secret to cutting a hexagon column is to start off with a blank that is about twice as wide on one side as the other and length can be whatever you want. Set the angle of your table saw blade to 30 degrees (which conversely is 60 degrees off the table) and make your first cut, then flip the board upside down and make the second cut.
You now have an oblong board with V cut along one side. Next you will need to measure how far to set the fence from the blade. To do this we simply need to measure the width of one of the V cuts you just made and mark that distance on your table saw from inside of where the blade will be cutting and the fence. Now to cut the second part of V cut, flip your board so that the V you just cut will run along the fence of the table saw. Now line up an invisible line between the two outside edges of the V cut, with the mark you just made on the table saw base and align your fence to meet the column. From there you simply make your cut along the side of your oblong board, flip it upside down for the second cut and presto - a perfect hexagon column.
Sliding Dovetails are easy but they can be a bit time consuming if you only cut them once in a while because they need to be re-set each time. Or you could build a jig or two if you use them a lot. The first thing to make is your dovetail slot. The best dovetail slot is one where the bit slices through the wood and leaves a perfect dovetail cut. If the bit is too high there will be a bit of ragged base or opening. The opening slot should be a clean cut. If the slot is too shallow you may not get as good a connection when you cut the dovetail pin or rail. When you are satisfied the dovetail slot is what you want, go ahead and make all those cuts because you will need to re-adjust the router table fence in order to cut the sliding dovetail pins or rails when that time comes.
You should not have to reset the height of your dovetail bit in order to cut you dovetail pins or rails. You will need to adjust the fence on your router table back and forth until you get the perfect fit. The best way to do this is only adjust one end of the fence while the other end of the table is held fast. This way you can make minor adjustments back and forth with the fence and end up making perfect dovetail rails.
You will need to check your dovetail rails in the slots with each adjustment so make sure that where the rails slide in to the slots that there is a clear entrance way otherwise you may end up cutting dovetail rails that are too loose.
With all this work you will be amazed how quickly you can make sliding dovetails, and just what a great way of joinery they are ....
Copyright - Colin Knecht