This project is continued from How to Fix Sagging French Doors – Part 2.
With the French Door removed from the doorway, placed in a jig on it’s side to hold it securely, and the old hinges removed, I’m now ready to install the new Hager BB1279 ball bearing hinges.
The Hager hinge has square leaves, but the mortise is radiused (i.e. has rounded corners) and is too shallow for the heavier gauge brass of the new hinge.
A wood chisel will make quick work of squaring and deeping the mortise to fit the new hinge.
Hot to Cut a Mortise for the New Door Hinge
The new Hager door hinge is aligned with the old mortise to be squared and deepened. A sharp utility knife (a pencil will also do) is used to lightly score the outline of hinge.
A very sharp wood chisel is used to cut along the lines marked with the utility knife. It is important the wood chisel be kept surgically sharp or you’ll just gouge and tear the wood. I use a diamond sharpening stone to keep an edge on my tools.
This is the hinge mortise after striking the corners with the chisel and hammer. One flat stroke of the chisel is all it takes to remove the corner wood pieces.
The Hager hinge leaf is much thicker than the original hinge leaf. The mortise must be cut 1/16 inch or so deeper for the hinge face to be flush with the door edge. The wood chisel is worked flat in the mortise to evenly remove wood shavings until the desired depth is achieved. Frequently check the fit with the new Hinge, eyeball and feel the edges, remove another layer of wood, then recheck the fit.
The hinge should lie flat (no high spots) and the hinge face flush with the edge of the door.
The steel ruler illustrates how the mortise is just deep enough for the hinge to be flush with the door.
The mortises on the door jamb are also squared and deepened to fit the new hinges.
Two of the holes on the new hinge do not match the old holes, and filled with fast setting two-part epoxy putty to strengthen the door edge.
This project is continued in Part 4, where I install the new hinges and set the door back in the frame.