Photo 8- This table saw miter jig will cut very accurate joints for
your tray. The jig is worth the effort to build well because you'll
use it in the future for other cuts. Use a flat piece of plywood for the
base, and carefully make and fit the runners on the bottom that ride in
the miter gauge slots so that the jig slides smoothly with no side to side
Miter the corners of the sides with a special table saw cut-off jig as in photo 8. This jig slides along the table top with runners attached to its bottom that fit in the miter gauge grooves in the table. Put two fences on the jig, as shown. Set both fences at 45o to the blade, but most importantly, be certain that there is exactly 90o between the two fences. Use one fence to cut one side of a joint, use the other fence to cut the other side. So long as the fences are at right angles, the joints you get will also be square.
You can also make this kind of cut with a miter gauge at the table saw. Various very accurate miter gauges are available, to see some of them click here.
You are also cutting the parts to length with this operation. The exact length of the parts is not critical, but it is important that parallel sides are equal in length. Make the short sides 11-1/2" long approximately, and the long sides about 24".
Photo 9- Cutting the kerf for the tray
bottom to fit into.
Cut a kerf along the inside, bottom edge of the sides for the bottom to fit into as in photo 9. Make it the width of a regular combination or rip carbide blade. Locate the lower edge of the kerf 1/4" from the bottom of the parts, and make it 1/4" deep. Use a push stick as shown to push the parts through.
Photo 10- Deepening the kerf on half
the ends for the splines.
You'll join the corners by deepening the bottom kerf at the corners only, and fitting a spline into the deeper kerf. Leave the fence in place after the last step. Raise the blade to 1/8" less than the thickness of the sides. Make a pencil mark on the saw table insert, adjacent to the blade, which shows you where the middle of the cut is. This is where the blade cuts highest. Now take each side, and deepen the groove on one end of each as shown in photo 10. Push the part in only until the front tip of the part just crosses the pencil line you drew on the table. Then retract the part.
Photo 11- Deepening the kerf on the
other half of the ends.
With the saw fence located as it is, you can make only half of the deeper grooves. To make the other half, turn off the saw, and move the fence away from the blade about an inch. Place one of the parts on the table in front of the blade, and set the fence so that the blade falls into the shallow groove. Now the top of the side is hitting the fence, not the bottom. Carefully set the fence so that the blade is perfectly aligned with the groove. Remove the piece, turn on the saw, and again cut deeper grooves, only pushing far enough that the tip just crosses the pencil line, then retract, as in photo 11.