Finger Joints
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Figure 3-71. The finger joint is attractive and has a great deal of strength because of its abundant glue area. |
The finger joint, like the dovetail, is often found on classic examples of furniture. It is sometimes hidden, but other times it is left exposed to denote craftmanship and display the interlocking fingers which form interesting patterns (Figure 3-71). Structurally, it is an impressive joint because it has an unusual amount of gluing surfaces. It is often called a "box joint" which doesn't exactly seem correct since the term connotes unimaginative applications. Actually it can be used on drawers, jewelry boxes, carcass constructions, and so on.
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Figure 3-72. Construction details of a finger joint fixture. Click on image to see larger view. |
Generally, the width of the fingers should be about equal to the thickness of the stock. However, on a shallow project made of 1/2" or thicker material, such heavy fingers would not be visually appealing. In many cases, even on deep projects made of thick material, thin fingers look more impressive. A good, practical finger width is 3/8". This will look good on material thickness ranging from 3/8" to 1".
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Figure 3-73. The fixture, ready for use, looks like this. |
Finger joints look complicated. But when you make a simple fixture, like the one shown in Figure 3-72, you can cut mating pieces of the joint at the same time and with ensured accuracy. So that the mating pieces of the joint will fit snugly together, be very careful with measurements and cuts when you are making the fixture. Note: The fixture is for 3/8" wide fingers only. For different size joints, the 3/8" dimensions need to be changed to the sizes desired. Warning: The upper saw guard is removed so work with extreme caution.
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Figure 3-74. (A) Make the first cut with guide strip between the work and the guide block. (B) Make the next cut as shown. Click on image to see larger view. |
To cut the notches in the fixture, set the dado accessory for a cut that is exactly 3/8" wide. Set the dado blade's projection to match the thickness of the stock or just a fraction more. Mount the fixture to the miter gauge and make the pass that cuts the first notch. Make a second notch exactly 3/8" away from the first one. The guide must be exactly the width of the cut and be secured in the second notch with a screw.
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Figure 3-75. Make subsequent cuts by placing the preceding cut over the guide. |
Figure 3-73 shows the fixture mounted to the miter gauge and ready to use. Place the spacer against the guide in the fixture and butt one piece of the workpiece (part one) against it. Make the first pass (Figure 3-74A). This first cut, which will be L-shaped, is then butted against the guide. The mating workpiece (part two) is put over top of part one. The uncut edge is butted against the guide (Figure 3-74B). Subsequent cuts are accurately spaced by fitting the preceding cut over the guide (Figure 3-75).
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Figure 3-76. Construction details of a finger joint fixture for various widths of fingers. Click on image to see larger view. |
The finger joint fixture that we have demonstrated will continue to serve anytime the joint will have the same finger widths for which the fixture is designed. However, you can make another fixture that allows multiple width fingers if you interchange multiple size of guides (Figure 3-76). Using this type of fixture will require more care, since the fixture must be accurately set for each job.
When using either fixture, any excess of finger length can be sanded off after project assembly.
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