Thread: Lock mitre router bit jig

Using a lock mitre bit can be tricky for joining the ends of planks. For example, when making a recessed kick board to go under furniture.
It is difficult to keep the work-piece straight as you move it across the router table.
This jig provides a solution and the idea can be used for similar situations.

You need a scrap piece of straight timber and some stock pieces of the same thickness as your work-pieces, and a small nail or brad. I used a 30 mm ´ 2 mm nail.

Screw the stock pieces to the straight piece so that they are separated by the width of the work-piece. Make them flush to the each edge of the straight piece, as shown in Photo1.

Photo1.JPG

I actually ran the jig through my table saw to take a little off each edge to ensure that the edges of the stock pieces and the straight pieces were flush.

Drill a nail hole of the diameter of your nail at an angle through one of the stock pieces, from underneath as shown above.

Enlarge the nail hole on the top side so that you can easily insert and remove it to secure work-pieces in the jig as shown in Photo2.

Photo2.JPG

Place the work-piece into the jig and tap the nail a few millimetres into the work piece to secure it in position. Note that I wrote which edge of the jig should be used upright and which flat on the router table to make sure I matched the ends correctly.

Now run the whole thing with a test piece across your table, assuming you have set the fence and height of the bit correctly. Of course, you will already have run a plain test piece through to check your settings.

Photo3 shows my test piece and jig after running through each way.

Photo3.JPG

The stock pieces in the jig now have the router bit patterns on each edge. In the future you can use the jig to set the height and fence position for this thickness more easily.
The corner of the straight piece of timber is just grazed by the router bit.

Pull the nail out to remove your work-piece.
Photo4 shows two pieces dry-fitted after using this jig. There is a small mark on the edge where the point of the nail has secured each piece, but it is difficult to see.

Photo4.JPG

The jig makes it easy to repeat joins.

Keep your jig to use again. For different width timber, just change the separation of the stock pieces, by moving the piece that doesn’t have the nail hole.
For different width stock, just remove these stock pieces and replace with ones of the correct width.