Popular Woodworking 2005-06 № 148, страница 36
The Trouble with Plywood Plywood however, does introduce some problems that you need to be aware of. The veneer face is very thin. You need to handle it carefully to avoid scratching it, and when you sand you need to be careful that you don't sand through the veneer. Despite what some people might tell you, the factory edges are not straight, and you should never assume that the corners of the sheet are square. The other problem with plywood is its thickness. It will be between V32" and Vl6" less than 3/4", and the thickness can vary throughout the sheet. If you cut the horizontal parts to the dimensions in the cutting list, your cabinet will finish slightly smaller in width. If you then cut the top and make the face frame to the listed size, they won't quite fit. The first thing you need to do is determine the actual thickness. Then develop a strategy for working around this discrepancy. I began by crosscutting the plywood at 60", as shown in the cutting diagram. This large piece will yield the two long sides of the bookcase and the back. The smaller piece will provide the top and bottom of the cabinet, as well as the fixed and adjustable shelves. There is a little extra room to allow for squaring the ends of the finished parts and cutting clean long edges. You can make this crosscut on the table saw, but it's easier to cut the full sheet with a circular saw and a straightedge. You could also make this first cut with a jigsaw, and then clean up the edge with a router. If you go this route, clamp a straightedge to the sheet, make sure it's square and run a flush trimming bit against it to clean up the cut. Make the first rip cut on the table saw V4" wider than the finished part. Then move the fence in to trim the opposite edge. Keep the best side up, and the freshly cut edges against the fence so that you have two clean edges on each part. After ripping, I crosscut the parts on a sliding compound miter saw, using a stop to make sure that pairs of parts were the exact same length, which is important. The plywood I was using was V32" thinner than 3/4", so I made the parts that go between the sides Vl6" longer than the listed length. One of the most important facts about plywood is that it is almost always thinner than the stated dimension. This (one of four types) 3/4" plywood was V32" undersized. This allows the cabinet to finish at the correct width. Develop a Strategy Look at the exploded drawing at right to understand how the parts of the basic carcase go together. The back sits in a 3/4"-wide by V2"-deep rabbet cut in the back edges of the sides, the bottom and the top. In the three versions with face The rabbet at the back edge of the cabinet sides, bottom and top is made with a stack dado set on the table saw. The featherboard holds the plywood down flat to the surface of the saw. The story stick, made from a scrap of plywood A second story stick acts as a jig to locate the bis- shows all of the cabinet parts at full size. Make cuit slots in the cabinet sides. Reference marks for one and put away your tape measure. Use it to lay the slots line up with the centerline on the bottom out all of the parts quickly and accurately. of the machine. With the cabinet on its side, I can easily reach both the front and back edges to keep them flush. Speed squares clamped to the side and shelves keep the cabinet square during this glue-up. I let the glue dry overnight before attaching the cabinet top. Because the top is placed above the cabinet sides I had to use clamps in pairs to hold the top down as shown here. 34 Popular Woodworking June 2005 |
