Fitting the Lower Registers this past week was more than a bit challenging. The challenge presented itself when I discovered that the pinblock supports were too short.This is the original maple block, coming up 1/2″ short. The lower register needs to fit perfectly between the dado in the rail (on the right) and there is a hole on the bottom side of the notch that accepts a screw to secure and allow adjustment of the register.
Fortunately they had (have) not been glued in yet, so they were removed and rebuilt to the exact size required after checking the plans at least ‘twice’. Mistakes happen! As it turns out, when I reviewed what went wrong I had taken the overall length from the bottom of the block where the ‘notch’ is cut instead of the top. So, this gave me a chance to make the blocks out of oak, same species as the pinblock itself. Here is the new block showing how the lower register fits snugly into the notch. The original plan called for a 6 x 3/4″ screw to secure the register, but it is in a very difficult place to use a screwdriver to put the screw into place, so I removed the blocks and tapped the holes with a 10×24 tap (which just basically threads the wood for a machine type screw). This solution makes it much easier to insert the screw once you put the register into place. This photo also shows more clearly how the register fits into the dado in the belly rail.
Tapping the pre-drilled hole was quite simple. Here you can see the tapped hole with a screw inserted on the right. On the left is a freshly tapped hole and below is a knurled screw that accepts an allen wrench (shown) and the tap itself is at the bottom of the photo. It is very important that the tap and the screw are the exact same thread size.
And finally here is what the lower register looks like installed.
Confessions of an Amateur Luthier 