A simple jig for adding splines to picture frames. This jig is made of MDF, but the material may not matter. I used three pieces of stock about twenty inches long and one of those pieces of stock is cut to the same width as your table saw fence.
The second piece is cut two inches taller than the fence, and the third is five inches taller than the fence. In the tall piece you can drill three two inch holes together horizontally an inch down from the top to form a handle.
Assembly
When you assemble the jig, use both screws and glue. MDF is soft, and this will work very well giving a solid finished product. Put the first piece of stock cut on the fence and line up the shorter side piece and attach, and then do the tall side with the handle up and attach with screws and glue.
Note: The tall side will be on the side of the fence closest to the blade.
You now have a U shaped with one side taller. We cut the stock so that the side pieces went above the center piece of stock, so we can cut scrap pieces to go on top between the two sides to strengthen the jig, giving it an appearance of having a tray on top.
Cut a thin piece of stock to the full length of the shorter side about one and one half inches wide and attach it to the bottom with glue. This will keep the jig from catching on the miter slots.
Now we will add the part of the jig that holds the picture frame. Do not glue this part of the jig since you may wear it out or just want to change the shape for a different frame. Two pieces of thin stock will be attached to the tall side of the jig. This will make a V shape, but the bottom corner of the V should have a gap and it will not come to a point. Note: You need to have room to line up the saw blade to cut through both ends of the frame miter joint so that you can glue in a spline.
Using your square line up the V with both pieces of stock, and make sure that your lowest screw is above the highest point that your saw blade can cut, then put the second screw close to where the stock comes to the edge of the jig.
Note: You may never use this jig with the saw blade set high, but you can prevent a mistake by dealing with it now.
After attaching the V, you should be able to put your square in the V and it will be true.
Using the jig
Clamp a mitered joint into the V. You might want to glue the joint first, but be careful since this kind of glue joint breaks easy. After it is clamped in place, bring the saw blade up so that it goes through the stock but not so far as to come through the joint into the area where the picture will be. Move your fence with the frame on it and the joint clamped in front of the blade and aim for the center of the thickness of the frame. This should also cut through the bottom of your V that is part of the jig that holds the frame.
Turn on the saw and push the jig through. Then put a spline in the slot.
Note: At Birmingham we used eight inch thick hardboard called Masonite for the spline material since it is the same thickness as the saw blade cut, it is actually outdoor hardboard, I use it at home, and I can buy a sheet for $9. Another note is that I glued felt inside my jig to help it slide a little easier.
Submitted by John Sherrer