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  • CMT Reverse Glue Joint Bit

CMT Reverse Glue Joint Bit

This router bit is designed for edge-jointing narrower boards to create wider panels for benches and table tops, door panels or shelving. It's a very serviceable item to have in the tool cupboard as it vastly increases the glue service area of the edges of your boards and gives the joint enormous strength. (Diagram A)

The difficulty with setting up this router bit is that the centre of your workpiece needs to be lined up with the centre of the router bit. As you can see in Diagram B, the centre falls at a point on the tapered side of the tongue. It’s hard to pin point this exact position and unless you have set up blocks for every thickness of timber you use. It involves a lot of trial and error getting it right.

Rod Childs makes small one-off furniture pieces and is always joining boards of various thicknesses. He decided to make a jig using some scrap aluminium that he had in the workshop. You could use plywood or timber just as easily.

The jig is a piece of aluminium bent to 90°. Using a metal cutting blade in a coping saw, Rod cut one side exactly to 12mm width and left the other side wider. He made a cut along the centre of the 12mm angle. (Fig.1)

Find the centre of your workpiece and mark it using a marking gauge or a pencil. Match up the cut in the centre of the aluminium finger to the marked centre line on your timber. Scribe a line against the outside edges.
(Fig. 2)

Now you have two scribed lines 6mm each from the centre. Match up one of these to the line up point on the router bit marked on the diagram B.

You will find this will place the centre of the bit at the centre of the workpiece. As you’re going off a clearly defined point on the router bit, it’s easy to do by eye. The thickness of the timber doesn’t change the set up at all as your reference point is always the centre of the board.

This set up should be just about perfect. If you find there is any adjustment needed when you cut your sample piece, it will only be the tiniest tweak.

Reverse Glue Joint Bit product page - Order no. 855.501-11