There is more than one kind of sled. Curtesy of Tom Vos The first type of cross cut sled might have a platform that spans the blade, with runners in both miter slots. This will provide for accurate cross cuts.
Why use a sled.
Since a miter gauge has a rather small face, it can be hard to keep a long board straight as it goes through the blade. But if you have a sled that extends out past both sides of the blade a foot or two, you will have more control. When you use a sled the wood lays on the sled instead of the saw top. When you push the sled through the blade the work piece you are cutting goes along for the ride.
On the front you will need to use a rather high back board,(fence) that connects the platform on each side of the blade and maybe one on the back of the platform too.
Note: When we use the terms front or back in this article, the front refers to the infeed side of the saw or sled, (the side closest to you), and the back is the out feed side, (the part of the saw or sled behind the blade.
The Parts of a sled
The platform or bed of the sled is typically made from one half inch birch plywood. The size is up to you, but for a dual miter track sled it should be at least twenty four inches wide.
It will have two runners for the miter slots. The runners can be made from hardwood, (preferably Maple for its hardness), metal or plastic. See links at the end of this page for part suggestions.
A front fence. The fence is typically made of hardwood. It must be straight and flat and at least as long as the bed is wide and at least twice the maximum depth of cut of the table saw blade.
Finally a rear fence or support. The rear support is not always needed. It depends on how deep, (the distance from front to back), the bed of the sled is,
By now you might have guessed that with a double miter track sled, the first thing you will do before you can use the sled is cut it in half. This is why the front fence and rear support must be tall enough to accommodate the maximum cut height of the blade and still have enough material left to support the two hafts of the sled. The typical height of the front and rear fence is five to six inches.
Sometimes a sled may be wide but not deep, (from front to back), say less than six inches. In this case the front fence is enough to hold the two halves together and no rear support is needed.
Single runner sled.
There's another kind of sled that I use for cutting larger panels. This sled is used with only one runner and is used on either the left or right side of the blade depending on how you make it. It can be of variable size, but two feet square would not be too large. Mine goes on just one side of the blade, and the wood strip that runs in the miter slot extends out past the front of the sled a ways.
If you want to trim off the edge of a larger panel that you've glued up, and you try it with the miter gauge, you will be pulling the miter gauge back off the saw top in order to get the blade into the panel.
With my panel sled, I can start two or more feet back from the blade, and still have good control over the panel as it goes through. I have a wood fence across the front of the sled that is set carefully to be square with the blade.
Added by Bob Kennedy
A cross cut sled can be purchased or you can build your own. When building a sled there are two things that are a must. The sled must slide in the miter slots easily but have know wiggle from side to side. Second the front fence must be perfectly square with the saw blade. If it is not, the cut will not be square.
The following link will explain a few different ways to build a sled. There is no one way to build a sled that is better than another, as long as the above criteria are met. You can pick one method or combine different ideas. Just use whatever you feel comfortable with.
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