The router makes it easy to install hinges into a door slab. Most doors have three sets of hinges that attach the door slab to the door jamb with pivoting hinges. For a door to seal tightly the hinges must be mortised into the door and jamb. The door will bind if the hinges are not set square when installed. With a plunge router and an easily made router jig you can install door hinges accurately and with relative ease.
Put on your safety equipment.
Use the table saw to cut a piece of 3/4-inch board down to 6 inches wide x 12 inches long. This will make the base for the hinge jig. Also cut a piece of 3/4-inch board down to 3 inches x 12 inches long. You'll use this for a clamping strip to hold the jig in place on the door when you use the router.
Use a tape measure and mark a center line on the jig's base you just cut. Refer to the specifications of the hinges to place them in the center of the jig. Temporally install it onto the jig's base as if you were installing it on the door's edge.
Use a sharp pencil to mark the hinge on the jig. Remove the hinge and add the thickness of the router bit guide collar. This should be 1/8 inch for most collars to the outside of the pencil marks.
Use a jigsaw or band saw to cut out the jig's base where you marked the hinge. Follow the outside line as your cut line.
Flip the jig over and use a tape measure to mark the width of the door slab onto the jig. Make sure you measure from the edge where you cut the jig. Use a straight line to mark the jig. Glue and screw the clamping strip to the bottom of the jig's base. Place it along the outside line of the door width.
Mark the center line location for each hinge on the door.
Attach the hinge jig to the door using the center line as a reference mark and clamp it in place.
Set your router with the 1/2-inch straight router bit and guide collar on the hinge jig. Lower the plunge router until the bit touches the door. Lock the router height at this setting. Use a hinge as a gauge to set the plunge router depth stop to the thickness of the hinge.
Start the router and plunge it to the depth stop setting you just set and router from left to right. The router guide collar will follow the template. Freehand the remaining material.
Move the hinge jig to the next hinge location on the door and repeat step 10 for all hinges.