Wooden HingesComments (0)
This article is from Issue 18 of Woodcraft Magazine.
Here’s a challenging furniture detail that’s utilitarian, attractive, and all-around impressive.
By Michael McDunn
IF YOU’VE GOT YOUR SIGHTS SET ON MAKING HIGH-END FURNITURE, wooden hinges are an impressive detail you’ll want to master. I regularly use the type of wooden hinge described in this article when crafting Pembroke-style drop-leaf tables.
If you desire a perfect match of grain across the hinge, begin with a single board that has been cut in half, and fashion the two interlocking halves of the hinges from the edges that were formerly connected. Begin with your two pieces of stock dimensioned to final thickness and width. I’m making a hinge with pieces that are ¾" thick by 3¾" wide, which will provide easy spacing for the hinge knuckles later on.
It is a good idea to leave your workpieces extra-long at this point, so mistakes can be erased simply by trimming down the board.
TIPS for TOP-NOTCH marking
- A standard marking gauge can be modified by sharpening the pins to a cutting edge. The result is a much cleaner marking line, especially across the grain.
- Focus on keeping the head of the gauge against the workpiece, as the blade will have a tendency to follow the grain, possibly pushing the head away.
- Hold the gauge head gently but firmly in place. Do not grip the gauge by the beam, as this may cause it to twist and pull away from the workpiece.
- It is easiest to maintain a straight line by beginning with the gauge at the edge furthest from your body, pulling it smoothly toward yourself. Tilt the gauge toward you so that the blade, beam, and head are all in contact with the workpiece.
- Applying a small amount of paste wax to the head of the gauge will help it slide easily across the wood.
MARKING THE STOCK
The success of the hinge will depend upon consistent positioning of its interlocking parts, so a common line of reference is necessary. Such a line is easily scribed with either a cutting gauge or a marking gauge; a cutting gauge is shown in the photographs.
Set the gauge to 3/8", or half the thickness of the workpieces. You can verify an accurate gauge setting by marking an edge of the board from both face sides; the marks will coincide perfectly if your setting is accurate.
Mark a line across all four sides of the working end of each piece.
The first shaping of the hinge knuckles on one workpiece will be done on the drill press, with the stock on edge. To create a target for the drill bit, on the edge of the piece use the gauge to create a second marking perpendicular to the first, on the edge of the workpiece (Fig. 1).
The accuracy of these initial markings is critical. Take advantage of the extra length of the workpiece and cut away mistakes until you obtain satisfactory markings.
THE FIRST ROUND
Rounding the edges that will become the knuckles of the hinge is performed on a router table. Install a half-round bit that matches the thickness of the workpiece. I used a bit with a ½" shank, but a ¼" shank is strong enough since only small amounts of wood will be removed.
Position the bit so that the half-round cutting edge begins at table level, and err on the side of having it slightly below table level. You will fine-tune the setting momentarily.
The fence does not need to be elaborate; I am using a simple 2x4 that has been jointed and planed with an opening for the bit, clamped directly onto the router table.
To calibrate the router table setup, take a scrap piece of wood through the following steps.
Position the fence so that the depth of cut is exactly even with the fence or slightly recessed (Fig. 2). You do not want the deepest part of the bit’s curve to cut significantly into the wood, because a small uncut surface on the board’s leading edge is necessary to maintain regular contact with the fence. If all of the original contact surface is cut away, the trailing edge of the workpiece is likely to receive an uneven cut when passing over the router bit opening.
Make the cut along the end of the board, passing from right to left across the bit (Fig. 3). Place a similar piece of wood against the trailing edge to reduce tearout.
Once the cuts are made, examine the newly rounded end. If the curves are not properly centered, adjust the height of the router bit up or down accordingly. Repeat this process as necessary until the routed curves are centered. Then make the cuts on your actual workpieces.
The overall shape of the hinge is completed by routing a chamfer along the base of the knuckles on one side of each workpiece. No further adjustment of the router bit or fence is necessary, but the cut requires the use of a 45° jig. Fig. 4 shows the plywood jig I put together for the process.
Simply place the workpiece on the jig with the previously routed surface against the fence, and take a right-to-left cut as before. Again, placing a piece of scrap against the trailing edge of the workpiece will help reduce tearout. Only one surface of each workpiece receives the chamfer cut. When assembled, the cuts should be on the same side of the hinge, on the inside side of the swing.
Cutting the knuckles
On the shaped ends of the workpieces, mark out the locations of the individual knuckles. My hinge has identically sized knuckles, two on one side and three on the other, so I marked five ¾"-wide sections on each workpiece.
The drill press is used to cleanly shape the outer negative spaces of the two-knuckle piece. Select a drill bit slightly larger than the thickness of the workpiece, either brad-point or Forstner.
Clamp the workpiece on edge under the drill bit with a vise or stationary fence. The initial cross-shaped marking that was made on the edge of the workpiece should still be visible; line it up directly under the center of the drill bit.
Drill through the piece until the bit is within 1/16" of the first knuckle demarcation, then turn the piece over and perform the same operation from the other side (Fig. 5).
Leave the clamping setup in place on the drill press, and move to the table saw.
We will shape the interior spaces of the knuckles with a dado jig on a table saw with a sled (or a miter gauge and attached board).
Set the dado blades to match the width of the knuckles (¾"), and to a depth slightly shorter than the final length of the knuckles.
The jig for accurately spacing the dado cuts can be made out of any available scrap board; plywood is an excellent choice. Follow these steps (Fig. 6) to create the jig:
Cut an initial dado through the board. Insert a ¾"-wide piece of wood into the previously cut dado, protruding at least ½". It should fit precisely and can be glued in place. This spacer piece is ideally obtained from excess length material on the workpieces, or from a board that was milled to size at the same time.
Place another ¾"-wide spacer beside the first. Adjust the position of the jig on the table saw until the blade is just beside the spacer piece, secure the jig in position on your sled or miter gauge, and cut another dado opening through the jig.
Remove the unattached spacer piece and your jig is complete. Be sure to try out your jig and setup on a test piece first. The depth of cut should have the blades passing just under the chamfered groove on the hinges. Err on the shallow side, since excess material can later be removed with a chisel.
Line up the edge of the two-knuckled workpiece with the edge of the opening in the dado jig and trim away the last bit of material left by the drill press.
Then, using the inserted ¾" peg as shown in Fig. 7, cut the remaining spaces in both workpieces.
With a carving gouge, carefully clean up the outer spaces on the two-knuckled workpiece (Fig. 8).
With a very sharp bench chisel, back-cut the interior spaces between the knuckles to make room for the corresponding parts of the hinge to move freely when it is together. The resulting interior spaces do not have to be attractive since they will be hidden once the hinge is together. However, the line at the chamfer along the surface of the hinge will be visible and needs to remain straight and smooth.
Inserting the rod
The hinge is held together with a metal rod. I prefer to use a 3/16"-dia. cold-rolled steel rod from a local hardware store.
Place the two workpieces on a bench, chamfered side up, and slide the hinge together. The line that was scribed across the surface (now shaped into the knuckles of the hinge) at the beginning of the project should still be visible. Manually adjust the spacing of the two workpieces until the scribed line is perfectly aligned (Fig. 9).
Install a drill bit that matches your metal rod diameter in the drill press, which should still be set up to clamp the workpiece. Clamp the aligned workpieces together on edge below the drill bit. The cross-scribed markings on the edge should still be directly below the center of the bit.
Begin drilling toward the center knuckle of the hinge in a series of gradual plunges. Withdrawing the bit after each plunge helps to clear woodchips and keep the hole straight. Once you have drilled to the halfway point, turn the workpiece over and proceed from the opposite direction exactly as before until the hole is complete.
Cut a piece of metal rod to a length just short of the width of your hinge. Mine is 3¾" wide, so I used a 35/8" rod. File or grind away any burrs. On a hard, solid surface such as an anvil, strike one end of the rod with a ball-peen hammer to flare it slightly. This flared end will create a wedge effect and prevent the rod from working out.
Disassemble the hinge and apply a small amount of paste wax to the interior faces of each knuckle. Reassemble the hinge and stand it on edge.
Ensure that the hinge is properly aligned and gently tap in the metal rod until it is flush with the edge of the hinge (flared end of the rod entering last, of course). Work the hinge back and forth several times to check for any binding or excessive squeaking. If necessary, disassemble and adjust.
Once you are satisfied that the hinge is complete and all major errors have been avoided or overcome, you are free to cut the ends of the hinged boards to length and perform any other required shaping.
Michael McDunn has been a professional woodworker in Greenville, S.C., for 30 years, specializing in custom furniture for both homes and commercial sites and antique repair and restoration.
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