We have an old house (100+ years) with original door frames. The top hinge on one door has come away from the door frame - the wood is split and soft, so the screws have no bite.
I'm thinking the best way to fix this, short of ripping out the whole door frame, would be to drill out the split wood, chisel it square, then glue in a new piece of wood for the hinge to be screwed into.
Is this a wise move or is there a better way?
The short answer is longer screws, plus some glue.
There should be plenty of extra room for longer screws on both the door and the jamb. If the hinges are brass, solid brass screws are best. Pre-drill. At the same time stick in a small strip of wood soaked in wood glue into each hole just to be sure. Toothpicks, chopsticks or similar dry wood work well.
For bonus points sand off the lacquer coating on any solid brass screws you buy, so they will tarnish faster and match your hinges.
I would find myself a 1/4" or 3/8" diameter toothpick. Drill out the holes to the same diameter as the toothpick, insert some glue, and tap the toothpick in with a hammer.
If you have difficulty finding toothpicks that large, Use dowel.
Since you say that the wood under the hinge and around the hinge screw holes has split and gone soft it pays to check the wood of the door jamb adjacent to the hinge mount location as well. If the wood there is not sound then you are likely looking forward to some more serious repair such as replacement of the jamb side board or the whole jamb.
If the adjacent wood is still in good condition it may be possible to cut out the the piece under the hinge plate and replace it with a new block of wood. Edge gluing of the block of wood into place will require a very close tolerance fit and ability to clamp it into place to get the strongest joint possible. The best side for the wood to bond well with the new piece is along the grain so make sure the insert piece has the same grain orientation as the jamb. Then you can clamp across the jamb and to do so it would be necessary to remove the casing trim along the hinge side.
I would not drill out and chisel the the opening to shape as it would be a lot of work to get the tolerance necessary for a decent wood glue bond to the insert piece. Instead I would use an oscillating multi-function power tool similar to that pictured below. Using the plunge cutting blade like the middle one pictured it would be easy to cut out the damaged piece from the jamb with nice straight and square cuts.
Once you have the new piece glued in place and you go to remount the hinge make sure to drill appropriate pilot holes for the hinge screws so as to avoid splitting the insert wood piece.
Longer screws in old houses won't work, you will just hit plaster. Pull casing, cut out bad, new block of wood to fill cut out, longer piece slid behind new piece between jamb and stud creating overlap on top and bottom.
Post is old but here's wot I plan as decisive "easy-fix" of grossly over-repaired(destroyed) frame hinge-points: - cut out offset T-shape at bad hinge-points in frame (multi-tool or sharp chisel) leaving as much at frame edge still viable (not essential but avoids reshaping) - shape similar replacement wood "jigsaw-style" piece to fit hole tightly - dowel (if depth of surround allows), glue and pin where hinge-screws wont hit This ought allow for stresses in 3Ds for lighter doors Will let you know how it goes
