Is there a more precise method for obtaining the correct hinge leaf placement?
Okay. Here’s a method that will dial your hinge spacing exactly. Are the old hinges still mounted on the door? If so, set it up in a position where you can get to the hinge edge easily. Cut two pieces of 1×2 or strips of 3/4 plywood about 78″ long (or about 2″ shorter than the door is long), and lay one on top of the closed hinges, with one end even with the top edge of the door. Holding it in this position, mark with a knife point or sharp pencil the points where each hinge intersects it, then flip it up 90 degrees and clamp the first hinge leaf to the strip of wood. Screw two hinge screws into the wood, just as if it were the jamb. Remove the clamp and insert two more screws. Move to the next hinge leaf and do the same, and then do the last one. Now you should have the strip hinged onto the door edge just like the old jamb was. So you can unscrew the leaves holding the hinges to the door, and screw the other strip to them with the ends of the strips flush, and then unscrew the first
