TECHNICAL REPORTS DA_Y'D_H_Al_E&_F_RED_M_,W_Ol_FF PERFECT SCARF JOINTS EVERYTIME ROB ERT F. CHAM BE RS, UN lYE RSIT Y 0F TEXAS, AU STIN Have you ever had occasion to cut scarf joints on a lessthan-perfect bandsaw? This simple scarf-joint jig will allow novice studio help to make a perfect scarf joint everytime. Not only will it look better in the finished product but it will also be stronger because of the almost perfect flatness of the joining surfaces. The basic tool for this jig is a router. In our shop we use a Black and Decker model 442M with a '%" standard, flat routing bit. The faceplate of the router has been modified slightly. This change will be described below. Construction of the jig should be clear from reference to drawing but make note of the following: a. Make the baseplate of the best 2 inch stock that can be obtained. It is imperative that it be perfectly flat with no warpage at all. If no high grade 2 inch pine is available invest in 5/4 stock clear white pine. Next, determine the widest piece of material to be scarf jointed and rip the baseplate material to the same width plus 1/32". Various widths can be accommodated by the same jig but thick· ness must remain the same. We have separate jigs for 1x4 and 2x6 stock (see Figure 1.). Each separate jig will require a separate faceplate. b. After baseplate on jig has been ripped and squared off to the desired length cut away one or both sides at the end away from the pressure block as shown on the drawing. Do not fasten the side guides to the baseplate at this point. This will allow you to use a C-clamp later to grasp the tip of the board being scarfed and keep it from warping upward (Figure 2.). Before assembling base to side guides drill two screw holes through the baseplate and counter· sink sufficiently so that the screw heads are flush with the surface. With a 2x baseplate and sufficient countersinking you can use two #8 x 1-'%" flathead woodscrews to secure the jig to the workbench. It is absolutely necessary that the jig be secured in some manner while working with the router. c. Determine the angle for the scarf joint as shown on the drawing. When cutting this angle fasten both side guide rails together with the bottom edges and both ends perfectly aligned. (You may want to screw them together temporari Iy.) Cut the bevel on the gu ide ra iIs 1/16" to 1/8" above the line and then use a floor mounted disc sander to carefully and accurately sand to the finished slope line. This will insure uniformity between the two sides and make for a perfect finished scarf joint. Leave the sides fastened together until all finish sanding has been accom· plished on the slope. d. Next, make a faceplate for the router. One quarter inch tempered masonite works well. Remove the old faceplate and cut a new one of sufficient width to extend be· yond the opposite guide rail when the bit is firmly up against one side or the other. The faceplate should extend about '%" beyond guide rail. The centerhole in the new faceplate should be at least 1" in diameter. Use the old faceplate (A in Figure 3.) to locate the mounting holes in the new faceplate (B) and be sure that the screwheads are countersunk. I FIG.1 Scarfing jigs and router faceplates for 1 inch stock (left) and 2 inch stock (right). C§!:J THEATRE DESIGN AND TECHNOLOGY FIG.2 OCTOBER. 1974 27