Making Wooden Hinges By Alex Reid - www.mokkou.jp Materials and tools used - 3.2mm straight router bit - 1/8 round-over router bit - Flush-cut straight bit (with bearing on bottom) - Finger-joint jig - Round-over jig - 2mm brad-point drill bit - 75mm x 22.4mm x 6mm ebony blank - scrap plywood for mortising jig - 3.2mm spacer x 2-2mm diameter brass rod (material is optional I prefer brass for this) In this tutorial for making and installing wooden hinges I use ebony blanks cut and milled to a specific size related to the size of my cutting bit. I use a 3.2mm (1/8 ) cutting bit mounted in my router table. The width of the blank will therefore be 3.2 multiplied by the number of fingers and slots. I want a hinge that has 4 fingers/3 slots and the mate will have 3 fingers/4 slots. So the width of my hinge will be 3.2x7=22.4. (You can also make them a little wider and cut to size on the table saw after slotting the finger joints). The length of the blanks will be any length desired but should be around 75mm (3 ) for ease of clamping and cutting on the finger joint jig. The thickness of the blank will be 6mm or if you are working in inches 1/4 will work well. (Here also you can use a thicker blank and re-saw later for a production run). 1. Make a finger joint jig like the one pictured in Pic 1. I use a quick and dirty jig so the face is a throw away piece for this use only, screwed on from the back. The faceplate height is cut to the same height as my blanks (this is important). Place two spacers between the fence and faceplate and rout a slot through the face (Pic 1). Flip the faceplate end-for-end and do the same (Pic 2). Remove the spacers, move the faceplate against the router fence and cut another slot only on the bottom this time. Screw the faceplate onto the jig. Place a 3.2mm key in the first and second slot (Pic 2). Depth of cut should be about 0.1 mm over thickness of blank.
Pic 1. Using two 3.2mm spacers to cut first index key slot Pic 2. With top and bottom index key slots cut
The blanks and the faceplate are cut to the same length for ease of cutting and stability. Because the blanks are long and narrow stability is an issue. Of course a clamp does hold the blank in place but having the extra key slot makes the job a lot easier, a little less fumbled and more accurate. 2. Place a blank in position (Pic 3) and begin cutting the joints. Flip the blank end-to-end and cut right to left until last slot is cut (Pic 4). Pic 3. With blank in first position.
Pic 4. Cutting the last finger joint on the first blank 3. As in step 2 cut the slots for the matching hinge. Start the first cut with a 3.2mm spacer between the key index and the blank, flip end-to-end and continue cutting right to left until the last slot is cut. Note: it is at this point you will see how much you have to trim the width to size if the blanks were over-size to begin.
Pic 5. Slotted blanks ready for round over 4. I do the round over after I cut the slots as I am using a flush-cut bit with my hinge held in a vertical position in a round-over jig. This way there is no chipping on the sides as there would be if you ran the blank over a round-over bit in a horizontal position and you have more control over the profile of the round over. To make the jig use a piece of scrap about 30mm thick by app 50mm wide and long enough to hold the blank. Round over the left side edge of one end and cut a rabbet to depth the same as the thickness of the blank (Pic 6 ). Round over with flush-cut bit (Pic 7).
Pic 6. Round-over jig with rabbet cut and round over on corner Pic 7. Round over with flush-cut bit.
5. Now we are ready for the last step; drilling the 2mm hole for the brass pin. A note to bear in mind here it is crucial that the hole is center top to bottom and side to side as the hinges or lid can bind or the lid will lift away from the box unevenly and be unsightly. Set-up your drill press and drill a couple of test holes to make sure. When you are confident all things are right, place the hinges in the together position with a spacer so they aren t touching. (I used a piece of letter paper folded once. This is app 0.15mm (Pic 8). Pic 8. Hinge ready for drilling a 2mm hole 6. Once the hole is drilled put a pin through and check hinge action. Look at the space between the end-points and mating hinge. As you move the hinge does the space stay the same distance or can you see lift or binding? It should stay parallel. The hinge should open to just over 90 degrees. Finally if all things are right take the pin out and cut to size with a backer board to prevent chip-out on the corners. I cut the ones pictured in Pic. 5 to 20mm. Put the pin back in, file and sand the sides till pin is flush.
7. Now the hinge is ready for installation. For this we use a hinge-mortising jig (Pic 9). Again I use a quick and dirty, throwaway style jig, nothing fancy. What is important here is the guides are square and the correct distance apart. The distance between the two guides on the X and Y axis will be router base size minus router bit diameter plus width or length of hinge. In my case 160mm 3.2mm + 22.4mm = 179.2mm for the width 160mm 3.2mm + 40mm = 196.8mm for the length The underside of the jig has a cleat positioned with a distance from the cleat to the center of the mortise equal to the distance from the bottom of the box to the center of the hinge pin. In other words you want the hinge pin to be centered on the opening line between the box and the line. Pic 9. Hinge mortising jig 8. Clamp the lid to the box and position the mortise jig into place. (Here I have marked center on the jig and box. Now it is a simple matter of lining up the two and clamping the jig into place (Pic 10)).
Pic 10. Hinge mortising jig clamped in position with box and lid clamped together 9. With a plunge router set to a depth half the thickness your hinge rout the mortises (Pic 11) Pic 11 Mortises routed
10. Now there is the option to square the corners of the mortises or round off the hinges. I prefer to round off the hinge corners. I do this on a disk or spindle sander. I routed out the mortises with a 3.2mm straight bit so the corners have a 1/16 radius. Careful you don t take too much off. 11. Check the fit and if everything is okay glue the hinges into place. (Pic 12). I use standard PVA glue careful to avoid excess squeeze out and overflow into the fingers. Apply clamp and let glue dry. Pic 12. Check the fit is tight, glue and clamp