Mortising – Putting a Hinge in a Perfect Pocket

Most of the doors a do-it-yourselfer is likely to hang in his home are the pre-hung variety. They come complete with jambs (the frame inside which the door hangs) and hinges already mounted, ready to install as a unit in a door opening. Buying pre-hung doors like these takes almost all of the work out of installation, but it also limits your choices. Most pre-hung doors are plain and simple. If you want something out of the ordinary, chances are you’re going to have to hang it yourself.

And that brings up the problem of cutting the little pockets or ”mortises” into which the hinges will fit. Ideally, a mortise should be as deep as the hinge leaf is thick, and should fit neatly and snugly all around the perimeter of the hinge. A neat mortise not only looks good, it also provides a certain amount of support for the hinge it houses.

The easiest way to cut hinge mortises is with a router and a template guide. A professional, who hangs doors all day long, probably has one of these rigs. He can slip it over the edge of a door and cut the mortises for two or three hinges, all perfectly sized and spaced, in a minute or two.

If you’re a typical homeowner, however, you don’t hang enough doors to make the purchase of such a guide practical. In that case, do what I do: Use a router, but use it freehand.

To make things easy, I always use hinges with corners rounded to a 3/4-inch radius. Then I cut the mortise with a 3/4-inch straight bit in my router. This automatically gives the corners of the mortises the same radius as the hinges. If I used square-cornered hinges I’d have to carefully cut square corners in my mortises, by hand, with a chisel. That’s more work, and more opportunity to make a mistake.

Once I have my hinges, I put my bit in the router, turn it upside down, open one of my hinges and lay it down next to the bit. I set the router so the depth of cut is exactly equal to the thickness of a single hinge leaf. The router is now set to the proper depth.

Next, I place my hinge in position on the edge of the door, and, holding it firmly with my left hand, I go all around its perimeter with a sharp utility knife. If you have trouble keeping the hinge from skidding while you make this cut, tack it down with a couple drops of super glue.

On a typical softwood door, it will probably take just a single pass around the hinge with your knife to get the job done. On hardwoods, you may have to take two or three passes. Try to cut about as deep as the thickness of the hinge, but don’t worry about being exact.

Now you are ready to rout. You’re going to want to get your face down close to the work to clearly see what you are doing, so by all means wear eye protection. Turn on your router, place its base firmly on the edge of the door and start routing. Try to cut right up to your knife mark. Cut slowly and keep a keen eye on your work. As you cut right up against the knife line, a tiny sliver of wood should peel up and tear free. That’s your signal that you’ve cut far enough.

Go all around the score line, watching for that sliver to tear free. Then go back and rout out the rest of the mortise. Be careful to keep the router base flat on the edge of the door. If you let the router rock, you will cut too deep.

Once your mortise is cut, the only other trick is to make sure you drill the pilot holes for your hinge screws in the right place. If you let your drill skid and slip out of position, your hinge will be mounted out of position, and all your careful mortise work will be down the tubes.

The best way to assure properly located screw holes is to make them with a self-centering bit like the one shown above. This type of bit runs inside a tube with a tapered nose that fits the countersunk holes in your hinge leaves perfectly. To use it, you simply hold the hinge in place, place the nosepiece of the bit in the hole in the hinge and drill.

Most good hardware stores sell these self-centering bits, with brand names such as Vix Bit or Vike Bit. But if you can’t find one locally, you can buy them mail order from catalogs, including from the Woodworker’s Store, (612) 428-2199, or Trend-lines, (800) 343-3248.

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Mortising – Putting a Hinge in a Perfect Pocket

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