The table saw is agueably designed for ripping wood, that's really whate it is best at, but that doesn't mean it can't be used for other things equally well. For many woodworkers, the tablesaw is first stationary tool they purchase because it is so versatile. Out of the box, they will rip and cross cut (with the appropriate blades) and even cut dado, with a small modification to the throat plate.
With many table saws, the mitre gauges are pretty standard and have small surface that accepts wood for cross cutting, still they work ok. For someone who is doing a lot of cross cutting and wants perfect repeatable results, a crosscut sled is the answer.
These are relatively easy to make requiring only a few items, such as a good quality plywood base (I simly used a quater sheet of plywood that was 2 feet by 4 feet), a couple of decent quality mitre blanks and lastly a couple of flat boards that can be used for the front and back. The front stabilizer board only needs to be flat on the bottom the inside and outside should be reasonably flat but since this is only to stabilize the sled, it's not important that it be abslutely flat. The back stabilizer board DOES need to be pefectly flat on the bottom and inside as well, so selecting materials for this is very important.
If you have access to thick plywood that is 2 inches thick or better, that is ideal, otherwise you will need to hand pick something that is flat. I found a piece of construction grade, kiln dried 2x6 that was 8 feet long that looked like it would work. When I got it home and cut it in half, one half was off a tiny bit, but the other side was perfectly flat, just what I needed, and it was dry so it's not going to move around on me.
The actual construction of sled is fairly easy, the first thing to do is to lay the mitre blanks in the mitre slots on your table saw. I prefer to NOT have my blanks bottomed out, so cut them a wee bit thinner. This means they need to be slightly elevated in the mitre slots so that when they are attached to the plywood base. I have seen people use pennies or washers to elevate the blanks, but I find that this method can leave gaps when the blanks are attached at all the places that didn't have support. To fix this I cut one or two strips of light carboard (as needed) to support the blanks the whole length. This way when they are attached to the bottom plywood they are all flat and even, all the way along. Attaching the blanks is fairly easy, depending on what you are using, If you are using the plastic blanks, it's important to countersink them first otherwise they can push themselves away from the plywood base with excruded plastic as screws are beind driven in. After the base is attached to the blanks, the unit should be sliding smoothly on the table saw top. If it's not, you need to correct that now, because it will likely only get worse as you go along.
Now is the time you could fasten the front stabilizer wood to the base. Since this wood has nothing to do with the actual cutting, it only needs to be flat on the bottom and well attached with screws every 4 - 5 inches along length of the sled. We don't recommend changing the tops of the front and back stabiliers to anything, but rather leave them flat in case you want to install other jigs or even slot bar for other attachments and accessories. The next thing that needs to happen is to cut a slot through the base of your plywood base, but not all the way from edge to edge. To do this position your plywood base so that it is about mid point over your table saw blade, which has been lowered below the table saw base. You will have needed to install a good quality cross cut blade on your saw prior, or do it now. Now with the blade lowered ** make sure the blade is NOT touching the plywood base ** and the plywood base somewhat centred, turn the saw on and slowly wind the blade up into base until the blade is a couple of inches high. Now move the base back and forth slighly to untl the base is cut most of the way across, but leaving at least 2 - 3 inches on each side. DO NOT cut the plywood base all the way through at this point.
When finished, turn the saw off and lower the blade all the way down back inside the saw housing. At this point you can also attach the back stabilizing board to the base BUT ONLY with one screw at one end (I prefer the far right end). Now with slot cut in the base, you will be using that slot to determine the postion of the back stabilizer board. I prefer to use 2 pieces of wood, one at each end of the slot, then postion a large carpeter's square along the two points. The base of the sled and the back stabilizer can now be positioned even to the square to give you a perfect right angle.
Now you can clamp that position and drive a screw from underneath on the far left side of the rear stabilizer board and make a cut to check to see if that position is correct. AGAIN ... do NOT cut all the way though the back of the back stabilizer board. If the cut is perfect, the jig is ready to go. If the cut is slightly off, reposition the back stabilizer board and re-cut until it is perfect. At this point you can now fasten the back stabilizer board all the way along and start using it.
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