I’ve been hard at work preparing the backboards so that they can be fitted to the boarded bookcase – this is the final stage of the build, so that all will be left once they are fitted is to make pretty and then apply shellac. I got the backboards dimensioned last weekend; there isn’t much to say that’s new about that process. I am using 5 backboards, subtly graduated in size and orientated so that with the widest two boards go at each end of the assemvbly, with the narrowest board in the middle. The variations in width (other than the middle board, the others are grouped in pairs of corresponding widths) is partially determined by the maple I have in stock, and partially to allow a good fit in the casework. Instead of working to any measurements, the overall width of the backboards will be determined by the width of the bookcase, and using the arrangement I currently have allows the middle board to be trimmed until I have a good snug fit across the whole assembly. For that reason, I have not yet cut the middle board to final width, as I want room to trim it.
The backboards are joined to each other with tongue and groove joinery, and nailed to the rear edge of each shelf. The outermost boards are also glued to the sides of the casework. I really like tongue and groove joinery for backboards and other situations where boards need to be joined but still allowed to move, such as the shelf for the Roubo workbench. A dedicated joinery plane (I use the Lie-Nielsen No.49 for 1/2″ thick boards) means that cutting this joinery is swift and repeatable.
The other reason I like tongue and groove joinery is that it provides a good opportunity to use a beading plane, which adds a little visual interest to otherwise plain components. I’ve had this Philly Planes 1/8″ beading plane for five years, and don’t get to use it as often as I would like. But it is perfect for adding a shadow line to tongue and groove boards (which is why it has made an appearance on the Roubo workbench, the Policeman’s Bootbench, our Boot Bench, and the Saw Cabinet, to name a few projects). This maple required a fine cut to achieve a good finish, and once dialed in the Philly beading plane siwftly cut a sweet little bead.
Finally, I eased the fit of the tongue in the grooves – off the plane the joint is “squeaky-tight”, and I don’t want to run the risk of snapping the delicate tongue when test fitting and dissassembling the backboards. A couple of swipes with a small shoulder plane is enough to ease the fit and minimise the risk of joinery implosion.
When I’m next in the workshop I will fit the backboard assembly to the casework, and glue and nail it in place. At this rate the bookcase will be complete and in use by the end of the month.