Long Stock, Short Fence
Routing long, stiff pieces such as handrails, presents a couple of problems. First, it’s very hard to get (or make) stock that’s extremely straight and 12' to 14' long. Second, a piece that thick won’t flex, so a featherboard isn’t going to keep it tight against your fence.
The solution? Use two short fences, each about 5" long. If your workpiece is slightly curved, the bend won’t affect the shape of the profile very much.
I also use short fences on my tablesaw in some situations. When ripping a board, internal forces may cause it to spread apart as it is cut. The right-hand side of the board then binds against the fence and the blade. Dimensional softwood lum- ber is much more prone to this problem than kiln-dried hard- wood, but you never know.
You should always use a splitter or riving knife on your saw to prevent kickback from this kind of binding, but you’ll probably get burn marks on the board’s edges. The binding may get so bad that you can’t push the board the rest of the way through the cut.
A short fence solves both problems. If I’m ripping cedar for an outdoor project, for example, I clamp a short sub-fence to the saw that stops right at the point where the workpiece clears the blade. If the board starts to warp, it has nothing to push against. — Cliff Thornton