Woodworker's Journal 2008-32-6, страница 69
Today's SHOP A cfoss-lap joint Is traditional for joining horizontal sash bars, called muntins, and vertical sash bars, called mullions. The joint Is strong, it positively aligns the hars, and it looks sharp. Window Grill Cutter Set Window Grill Cutter Set Woodline USA A number of bit vendors have specialized bit sets for constructing divided light doors and for making window sashes. A finicky aspect of any divided light construction is the sash-bar joinery. Do you cut tiny mortises and tenons for each joint or depend on the strength of a simple cope-and-stick joint? A cross-lap joint is traditional and strong, but it's tedious to cut accurately. Not anymore! Unbeknownst to us poor woodworkers, bit makers have come up with a pair of cutters that make this cross-lap doable. And easily doable, too! One bit is a 1/4" straight bit, the other a V-groover with the point clipped off. It cuts a V-groove with a l/4"-wide fiat bottom. Here's how the system works. Cut a l/4"-wide dado across the top edge of one sash bar and across the bottom edge of its mate. The depth of the dadoes is half the stock thickness. Next, use the modified V-groover to cut across both sides of both sash bars. Center this cut on the two previous cuts, and set the cut depth to leave a 1/4" of wood between them. When the cuts are done, the two bars should slide together. You have a strong and invisible joint. When you are making a grid of more than four lights, you do have to lay out the cross-laps precisely. Your router table setup I ' must enable ■ ** you to locate the cuts precisely from piece to piece. Cut the cross-lap joints before routing the profile and the rabbet for the glass. The profiling cuts parallel to the grain, so it'll clean up cross-grain blowout from the joinery cuts. Finger Joint Bit You've seen paint-grade moldings at the home center — the stuff made up of those short pieces joined end-to-end with finger joints. Have you ever thought how great it would be to "stretch" a board like that? Did you know you can cut that joint on your router table? The finger joint is a positive-negative interlock, in which tapered projections (the fingers) on one piece fit into tapered grooves in the other. It expands the glue area threefold, but more importantly, it exposes long grain surfaces for gluing. That's why it works for end-to-end joinery. Miters glue poorly because you're bonding end grain to end grain. Mill the ends with a finger-joint bit to create oesting long-grain surfaces, and the miters will glue up tight and strong. It works great for miter joints as well as for joining plywood panels to each other and to edge banding. The bit that cuts the joint is not cheap, and when you see it, you understand why. The Sommerfeld bit comprises a stack of four-wing finger cutters and a thicker shoulder cutter, along with a ball beating guide on a 1/2"-shank arbor. The full assembly is impressive, though at just over lVs" in diameter, it can be run at full speed in a 1V2 HI3 router. Out of the box, the bit has five finger cutters stacked atop the bearing and capped with the shoulder cutter. You must reorder the stack according to the stock thickness. For example, you use only two finger cutters and the shoulder cutter to mill stock that's 5/8" to 13/16" thick. Today's Shop continues on page 70 ... Finger Joint Bit Sommerfeld Tools Best known for end-to-end joioery, the finger joint also reinforces miter joints, joins plywood pieces edge-to-edge and attaches edge-banding to sheet goods. ■ 68 December 2008 Woodworker's Journal |
