of all, the parts must be machined to precisely the same width and be dead on square. The stop used to set the cut must hold its position exactly. If it is bumped and moved even the slightest amount all subsequent cuts will be unacceptable. The cut must be backed up with a fresh material to avoid blowout. And this last one may seem simple, but it is a common cause for woodworking grief. Be sure the stock is accurately registered against the stop. The slightest bit of crud lodged in the way can cause big trouble. Blow out the area around the stop after every cut.
Cutting the Fingers
To start with, set up the widest possible dado in a sled, to a cutting height of 1¼". Clamp fresh back up material to the sled and set a stop to create a 7⁄8" “notch cut.” Make a test cut with scrap material and check the cut for accuracy. If your dado head is good and sharp (unlike mine at this time), you should be able to make the cut without band-sawing away any of the material. If you are having difficulty pushing the material through, go ahead and relieve the cut first. Once a good cut is achieved, run the actual base stock, first cutting on one side then flipping edge for edge and repeating the cut on the other side.
A. Base Fingers
Layout for round-overs, ebony peg locations,and size of fingers.
3. Making matching fingers.
4. Lay out the centerlines.
To make the matching fingers, move the stop over so that it makes a cut 7⁄8" in from the edge. Run some scrap stock making two passes (as before) first referencing off one edge then the other. There will be a small amount of material left in the center; for now just use a band saw to remove it. Test the cut against the previous cut for fit. Adjust the stop as necessary until the two pieces fit together with only a slight bit of friction. Run the actual base parts, referencing off both sides, then remove the stop and make one final pass to remove the uncut material in the middle.
5. Enlarge the hole incrementally.
6. Measure the hole as you get close to the correct size.
7. Remove the debris.
Cutting the Holes for the Ebony Plugs
It is easier to make ebony plug holes while the fingers still have their square reference. All holes are centered on the width of the individual fingers, but not on their lengths. Lengthwise, the holes are centered on the width of the mating base member. Start by laying out the centerlines as seen in the Base Fingers drawing.
For the ¼ x 7⁄16" hole, also pencil in the furthest extents of the rectangular shape. Make the square holes, as described in Chapter 4. For the rectangular holes, first make a normal square hole in the center of the layout. Working out from the center, using both a square, or square saddle, and the existing hole to correctly register the punch. Enlarge the hole incrementally until the extended pencil lines are reached. Be sure to creep up on the pencil lines slowly and start measuring the hole as you get close. Use a dental pick or similar tool to remove the debris left from enlarging the hole. Alternatively, if a quantity of the same size rectangular hole is needed, you may opt to make the punch guide described in Chapter 4.
8. The radiuses for all the edges.
9. Extend the 1⁄8" radius into the inside corners.
10. Mark a centerline down the face of the finger.
Adding Shape to the Fingers
Refer to the Base Fingers drawing (above) and Photo 8 to apply the appropriate radiuses to all the edges. With a seesaw motion, use a folded piece of 150-grit sandpaper to extend the 1⁄8" radius into the inside corners where the router bit was unable to reach. Mark a pencil line down the center of the end-grain face of each finger. With a folded piece of 80-grit sandpaper, and again using a seesaw motion, blend the flat face of the finger with the radiused edge. Keep sanding until the pencil line is removed. Continuing with the 80-grit, blend all the edges around the perimeter of the face using a sort of flapping motion backed up with your thumb. Viewing the fingers from various angles in strong light should identify any facets or lines that need to be blended in. The end result should be a seamless transition from the flat sides to the pillowed face. Once the desired shape is achieved, follow through with the sanding up to 320-grit.
Assembling the Joint
Working first on the two opposing joints along a single side of the base, apply a small amount of glue on the mating surfaces and use a corner clamp or similar squaring device to hold the joint square. Run a single trim head screw (#7 x 15⁄8") into the cavity of the center rectangular plug hole. Do not run screws through the smaller two fingers—they tend to split easily. If you do choose to screw the smaller fingers, be sure to pre-drill and be careful not to sink the screw in too deep.
11. Using a seesaw motion, blend the flat face of the finger with the radiused edge.
12. Using a flapping motion, blend all the edges around the perimeter.
13. Use a single trim head screw.
14. The finished base finger joint.
Finish off the base by making and inserting the ebony plugs (see Chapter 4).
Any
