Finger Jointed Box Page 2 of 3

Simple box with finger joints cut on a router table.


The finger joint jig for router table consists of a simple buttressed arrangement which will hold a piece of work at 90 degrees to the table. It has a sliding tongue underneath that fits the slot in the table top. In my case the tongue was made of wood and required a width adjustment for winter and summer variation. This was arranged by cutting a slit in each end and altering the width by screwing a brass m4 machine screw in one side of the slit which pushed against the other side thus increasing the total width of the tongue. It would have been easier to make the tongue out of metal!
The faceplate of the jig is an 18mm thick piece of ply which is slotted to move left and right by means of screw adjusters at each side, and locked to the jig with wingnuts. It is designed for 1/4 inch joints, so the peg and cutter are both 1/4". The cutter is a Leigh spiral solid carbide type to cut cleanly as possible. The silver steel peg is set 1/4" away from spiral cutter to give a 1/4 inch finger. You cannot cut joints less than 1/4 inch deep so if using thin material, allow for fingers to protrude and be trimmed down.
To commission the jig adjust the faceplate sideways until the gap between the cutter and the peg is as close to 1/4" as possible. Lock the jig and slowly cut the slot in the faceplate by moving the jig over the spiral cutter. Make several passes until it's 15mm deep (or whatever the max depth of joints you will cut. Make test joints on as belowusing scrap pieces. If the joints are too tight, adjust the faceplate so the gap is reduced a fraction, and try again. And vice-versa if too loose. Hopefully the slot in the faceplate will only be slightly oversized whrn you have finished all this.


In my web page Finger Joint Trick" it explains the sequence of cutting the joints.
Set the cutter protrusion with the depth gauge as per previous page.
Starting with end numbered "1" with the number facing outwards (so you can see it) place the edge against the steel peg. The jig should be to the left of the cutter so the cutter is exposed. Holding (preferably clamping) the piece to the jig, move the jig towards the cutter and slowly cut the first notch. Remove the work piece and carefully move the jig back to its starting position. Place the new notch over the steel peg and repeat until all notches are cut.


You should keep hands well away from the cutter and use BOTH hands to hold the work piece. This has its excitement and can result in the piece being flung about if you are not very careful. Slower but safer is to use a clamp.
Make absolutely sure that the end is fully down on the table or short notches will result.
Cut all the side pieces, reversing the pieces according to the Tricks page numbering schema.
Take note if the numbers should be facing out or facing in, according to the schema.
When the mating piece is cut, you must have the FIRST notch of the already cut piece on the peg and hold the new piece against it to cut the first notch of the new piece. That is why the facing-in/facing-out schema must be followed rigorously. Make sure the numbers are as per the Tricks page.
If all is well the box should assemble.