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Knife hinges aren't all created equal. The hinges on the left and right are stamped steel with a riveted pivot pin, making them nearly impossible to install accurately. In the center is a Brusso hinge, well-machined and much easier to install.
Installing Knife HingesLearn Fine Woodworking contributing author Gary Rogowski’s technique for super-solid knife hinge installation.
The straight knife hinge is used in situations where the top and bottom of the carcase extend over the door frame, and the door frame covers the carcase sides.
An L-shaped knife hinge, like the one seen here, is used on full inset doors. The short leg of the hinge, into which the pivot pin is set, moves the pivot away from the carcase so that the door can swing clear of the carcase side without binding.
Accurate Placement is Key to SuccessLaying out the mortises for either type of knife hinge involves essentially the same steps. Layout is the most critical part of setting them. Installed correctly, knife hinges will hold a door true to the face of the carcase and establish a consistent reveal between the door and the carcase sides all the way around. The key to achieving both of these goals is accurate placement of the hinge leaves. This comes down to a precise hinge setback in both the carcase and door and shimming the door hinge against the carcase wall to set the reveal.
Hanging a door with knife hinges begins with making sure the dry-assembled carcase’s face is flat and square. Before gluing up the carcase, lay out the two carcase hinge mortises, disassemble the carcase and then rout and pare the hinge mortises. Glue-up the carcase, and then let the glue dry, checking again to make sure the carcase is square across its opening. Plane or sand the face of the carcase flat.
Doors Should Fit SnuglyThe door should be built to fit snugly in the carcase opening. Trim the door, so it just fits in the opening with shims along the bottom rail and the hinge stile. The shims should be the same thickness as the washer that separates the two leaves of the hinge (leave the handle-side stile and top rail right for now). At this point, you’ll have mortises in the carcase and can cut the mortise in the bottom of the door. You’ll be laying out and cutting it in much the same way you did for the carcase.
The next step is to put hinge leaves into their mortises. A friction fit should keep them in, but you can tape them in if you like. Put the door into the carcase opening with the bottom hinge connected. Check and mark the reveal again on the bottom, hinge-stile side and on the top, as necessary. Plane or sand the door’s edge to get the reveal right on these three sides. Then lay out and mortise for the top door hinge.
Screw the carcase hinge leaves and the bottom door-hinge leaf into place, but be sure to drill and cut the threads first by screwing steel screws of the same size into the screw holes. This keeps the brass heads of the screws that come with the hinges from marring or stripping.
The final fitting of the door will be done with both hinges in place but left unscrewed. Hold the top door-hinge leaf on its mating leaf in the carcase while you set the door into the lower hinge pin. Slide the top of the door onto the door-hinge leaf (see bottom photo on this page). Close the door, and check and mark the handle-stile reveal. Open the door, slide it off, plane or sand the door’s edge to get an even reveal all the way around and reinstall the door. The door-handle stile can be trimmed back at a slight angle to provide clearance for the door as it swings past the case
For more information on hinge installation, be sure to catch Gary Rogowski’s original article from Fine Woodworking #111. Plus, read the first installment of this series-How to Install Butt Hinges.
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Not sure if the author or anyone will be checking in, but can anyone offer trouble shooting advice and a little more guidance on installation? For example, are the pin hinges always in the frame/cabinet and the open/female pieces in the door? If pints start to jam or tighten, what might cause that?
Sorry for such rookie questions, but you'ld think $25 hinges would come with at least a little instructions! We aren't all seasoned pros... alas... :-)
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