We could make tongue and groove boards with a router table and a special tongue and groove router bit set that is ready to cut the grooves and tongues to make these wood joints. Something that seems quite simple. But not everyone has a router table and one of these special tongue and groove router bit sets. That is why in this post we are going to see how to make a jig for routing the tongue and groove joints using the plunge router and without a tongue and groove router bit set. So, I am only going to use a simple slot cutter router bit with bearing and a straight router bit.
Jig for routing tongue and groove joints with the plunge router
In this case I am going to make a tongue and groove jig to route two different sizes of planks, to make tongue and groove wood. So, first I have to put the long plank 1 that I want to route with the edge slightly overhanging the edge of the board on which I am making the jig. And against that plank I screw a wood strip A of the same thickness or a little less thick than the planks I want to route.
Now I have to put the other plank 2 that I want to route in such a way that I align the end grain of 1 with the end grain of A according to the line LA1 (that is the edge of 2). Finally I screw the stops B and C so that B, 2, 1 and C are perfectly aligned along the line LN2. Now I only have to screw a small stop behind 2 so that it does not move back when routing.
In the next post we will see how to make the jig in case all the planks are the same dimensions, which will be the most common when making flooring and other projects. This was a test to see how the tongue and groove router jig works.
How to route the grooves of the tongue and groove joint
Now I can install the slot cutter router bit and adjust it to route a slightly off-center groove in the edge of the planks.
Thus, in a first pass I can route the edge of plank 1 and the head of plank 2. Then I just have to flip both plank 180 degrees and route again the groove on the same edge and on the same end face. In this way I will make perfectly centered grooves.
Now I have to route the groove in the edge of the short planks (planks 2), for which I put the two short planks in line in the place of board 1, and hold them with a new stop. And I make a groove in one pass, flip the planks 180 degrees and finish routing them in a second pass.
How to route the tongues for tongue and groove joints
To route the tongues of this joint I will use a straight router bit. I install it in the plunge router machine and I want to adjust it so that the end of the cutting edge is slightly below the groove (as shown in the picture).
Now I put the planks in the same way as I put them to route the grooves, but taking into account that I want to make the tongues on the opposite edges to the ones where I routed the grooves. In order to make tongue and groove joints, I have to route two grooves and two tongues in each wooden board.
But before routing I have to mark a depth for the tongues slightly shallower than the depth of the grooves …
and adjust the side fence of the plunge router machine.
And just like before I route, flip the boards 180 degrees and route again. In this way I will make tongues that are centered on the edge of the planks. Although in this case it may be advisable to route each side of the tongues in two passes. Like that we would put less strain on the router machine and also would reduce the possibility of wood splintering.
But the first thing to do is to route a corner and test how well the tongue fits into the groove. And I will have to adjust the routing depth, very gradually, until the tongue fits perfectly. The way I adjusted the routing depth, the tongue will be a little too thick, so I have to increase the routing depth little by little and test until I get both parts of the tongue and groove joint to fit well. Once they fit, I can route all the tongues following the same steps I followed for routing the grooves.
In this way I can route the grooves and tongues on the edges as well as on the ends of the planks. Although this was only my first try to make these tongue and groove joints using this router jig. In the next post we will see how to make these wood joints in planks that are all the same length. And I will route all the planks on all their edges and ends, so that I could use them perfectly to make a wooden floor.
I never imagined that making tongue and groove wood could be so simple.