I needed a 20″ wide board for the built-in project I’m working on, but like most people, I don’t have access to 20″ wide boards. At least not in my price range. So the solution to this problem is to edge glue two or more narrower boards together to make a single wide panel. I prefer to do this with as few boards as possible so I choose the widest boards I can that will result in the panel width I need.
Before gluing two boards together, it is vital to know which direction the face grain is running. If you get the two boards glued together with the face grain running in opposite directions, planing the final surfaces true after the glue has dried will be difficult due to opposing grain at the glue joint.
Notice here that I’ve marked the grain direction of the two show faces as well as the two joining edges. The direction of the edge grain is also important to know as it is helpful to have the grain on both edges running in the same direction when match planing the edges. However, this is not always possible with every pair of boards and becomes more difficult when edge gluing more than two boards. It is not as import as having the face grain running in the same direction and also flowing together well. The edges will be hidden in the joint so a little tearout will not be seen. If you cannot orient the boards with the face grain and edge grain running in the same direction, choose to run the face grain in the same direction if the appearance of the final panel will allow it. The appearance of the final panel should be the main priority. You want the grain from the two boards to flow together on the show faces so that the edge joint almost disappears after glue-up. If your final panel will be painted like mine, this is less importand and you can orient the boards with the face grain running in the same direction regardless of final panel appearance. On my boards, I was lucky to be able to get the face grain and the edge grain of the two boards running in the same direction.
The first step in creating a seamless edge joint is to plane the show face of each board flat and true. This will be the reference face so it must be fairly flat. Slight cupping is ok as long as it can be clamped out when the two boards are placed face to face, however, for this process, flatter is better. It is only necessary to plane one face at this point, the show face. The bottom faces of these two boards are still in the rough.
After the faces are planed flat and true, orient the two boards how they will be in the final panel. Next, fold the two boards together like a book with the show faces touching each other. In this picture, the edge facing away is the edge that will be joined together. Notice the rough area on the near edge of the upper board. This will be cut away after the panel is assembled so I’m not concerned with it now. This is a good place to use damaged boards like this.
With the two boards face to face, align the edges to be joined as best as possible to minimize the amount of planing. Use a pair of handscrews to hold the boards in position and place the pair in your vise or clamp to the front of the bench. Notice here how the edge grain of both boards is running in the same direction. I got lucky here but if I couldn’t get them running in the same direction I would take a lighter cut with my try plane to minimize tearout in the edge that was being planed against the grain.
I start with the try plane to clean up the rough sawn edges and plane both edges at the same time. This plane will also begin to straighten the edges. The iron is cambered slightly as this plane is also used to true board faces. I don’t like to glue panels up right from the try plane due to the cambered iron. I could just use my staight ironed jointer, however, it is set for a very light cut and therefore would take a lot longer to clean up the rough sawn edges. Starting with the try plane, I can take a thicker shaving to clean up the edges and then refine the edges for gluing with the jointer.
After cleaning up the rough sawn edges with the try plane, I refine and straighten the edges with the jointer. This iron has a straight edge for a tight glue joint. Again, plane both edges at the same time. A good practice when match planing edges like this is to begin planing only the center few inches of the boards. When the plane no longer takes a shaving, lengthen the stroke slightly. When the plane again stops cutting, lengthen the stroke again. This creates a slightly concave edge. Finally take full length strokes. At first, the plane will only cut at the start and end of the stroke (the high spots along the edge). Gradually, the shavings will begin to lengthen until you are taking one long full length shaving from end to end. When you get to this point, stop. You are done. The edges of the two boards will be straight.
A common misconception when creating an edge joint is that the edges of both boards need to be square. When jointing by machine this is true as the reference is the machine’s fence. However, when edge jointing with hand planes using the match planing technique, the edges do not need to be square. The reason for this is that any angle created by the plane will be cancelled out when the two boards are opened back up.
The picture demonstrates this with a very exagerated angle. The angles of the two board edges are clearly not 90 degrees, however, the resulting angle between the two boards when the “book” is opened up into a panel is 180 degrees, or a flat panel. This is because the angles created during match planing are complimentary. This method works every time as long as the thickness of the two boards together is not wider than your jointer plane’s iron.
Here’s the final result. These boards are not glued up yet. The top board is just sitting on top of the bottom board. The joint is tight, there is no light showing between the two boards. The resulting panel is flat and the show face will require very little cleanup. All that will be left will be to plane the rough sawn back side of the panel after the glue dries and cut the panel to final dimensions.