80 - Heirloom Tool Cabinet, страница 44
sriViiWKMH:!' Table Saw The secret to clean, crisp dadoes is using a few simple techniques. Cutting dadoes on the table saw with a dado blade is something I do all the time. But I try to never be routine about it. Because I've found that there's a nasty problem that can pop up. You can set up, carefully make the cut, and then flip the workpiece only to find that the shoulders on both the face and the end of the cut are rough and ragged with tearout This can be a problem on any type of wood, but plywood can really give you fits. Why Tearout in Dadoes? There are a couple reasons why tearout Anatomy of Dado TearoutChances are, if you've ever cut a dado on the table saw, you've been a victim of "dado" tearout. It shows up on the surface of the work-piece along the shoulders of the dado cut (Side View at right) and on the edge of the work-piece where the blade exits the cut (End View at right). The symptoms are pretty obvious — chips of wood that are roughly pulled loose from the surface instead of being cleanly cut. When the joint is going to be exposed on the project, this can end up being a lot more than just a minor aggravation. occurs on dado cuts. They both have to do with the dado blade and how it cuts. As the drawing below shows, a cut with a dado blade isn't a through cut. The blade is essentially trapped in the workpiece, surrounded by wood on all sides. This makes it harder for the blade SIDE VIEW tearout along shoulder of dado y 5HALL0W CUTTING ANGLE CAUSE5 TEAROUT to clear chips and dust from the cut. To compensate for this, a dado blade usually has fewer teeth and wider gullets on the outer scoring blades. But fewer teeth on the blades can mean a rougher cut. And then consider the cutting angle of a dado blade. For a dado, the cutting angle will be shallow and the blade ends up pushing forward into the wood instead of cutting down on it. This hammering action is more likely to blow out the wood fibers instead of severing them cleanly. The good news is that no matter what kind of dado blade you use, there are some quick and easy precautions you can take to avoid tearout. sure-fire ways to Avoid Tearout in Dadoes 44 ShopNotes No. 80 |
