Popular Woodworking 2002-02 № 126, страница 26
Ingenious Jigs For the crowned bars to work properly, the assembly must rest on a flat, rigid surface such as a workbench. Be careful not to over-tighten the clamps. If the middle of a bar lifts off the assembly, the clamps are too tight. a frame or a box square to one another while the glue dries. I have even used them to hold large boards — too large to fit in a vise — while I worked the ends or edges. Clamping Face-to-Face Occasionally, I need to clamp two boards face to face. This is a simple chore when the boards are narrow, but it becomes more difficult as the boards grow wider. Even deep-throated clamps have a limited capacity that may not reach to the center of wide boards. Consequently you won't get an even clamping pressure all across the width, and the assembly will be weak in the center. You run into a similar problem when trying to attach veneer or marquetry to a wide panel. How do you clamp the center area? For years, I solved the problem by keeping a 10" stack of concrete blocks outside the shop. When I needed pressure in the center of a wide assembly, I stacked blocks on it. It works, but it's inconvenient and somewhat limited. A better solution is to make a set of crowned bars. These are hardwood bars, 24" to 36" long, with one convex edge. This edge is Grooved wedges are useful not only for putting projects together but also for taking them apart. Here I'm using the wedges to pop the joints of a wobbly chair as I prepare to restore it. crowned only slightly, about 1/16" to VS" wider in the center than it is at the ends. I cut a crown by raising the outfeed table of my jointer a few thousandths of an inch above the knives and jointing the edge. You can also create a crown with a band saw, hand plane or a disc sander. To use the crowned bars, lay the assem 1/8" thick x 3/8" wide spline Grooved Wedges 1/8" wide x 3/i6" deep grooves 1 3/8" approximate Crowned Bar 1 1/2" 24 Popular Woodworking February 2002 |
