A cross-cut sled for the table saw is a must have jig for any serious woodworker. More accurate than a miter gauge, it also makes cross-cutting any board easy and safe. However, in order to provide the proper results it must be built with care. I made my first sled last year, following a plan in a popular woodworking magazine. Yet, in a matter of months, the maple runners swelled so much that the sled wouldn't slide in the miter slots. That's when my type "A" personality kicked in and I became determined to learn all I could about the ins and outs of building a cross-cut sled that would last. That research forms the basis for the tips and techniques presented in this instructable. And, while I can't take credit for any of these great ideas, I think you will find the insights of some very talented woodworkers helpful.
Step 1: Tip 1: Milling the Sled Runners
The runners ride in the two miter slots and guide the sled as the workpiece is pushed past the blade. They are most often made from hardwood such as maple or white oak, however, steel, aluminium or plastic runners are also options. Wood runners are more commonly suggested, most likely, because of the moderate cost. The disadvantage of wood runners is that the wood can swell with changes in humidity making smooth travel through the miter slots difficult or impossible.
Tip #1: Since most wood movement is with the grain, mill the sled runners with the grain running vertically as shown in the photo. This will minimize or eliminate side to side expansion of the runner in the miter slot.
Miter slots can vary slightly in size but most are 3/4" wide x 3/8" deep. Most plans call for milling the runners for a snug yet smooth sliding fit with no side to side play (also called slop). However, if the runner width swells too much it can become a problem and, as I mentioned, this is where I ran into trouble with my first sled. The good news: Tip number two allows some wiggle room when milling the runners to width.
Note: The height of the runners should be less than 3/8" so there will be some space under the runner for sawdust debris