Monday, October 31, 2011

Trick Or Treat?

Welcome to the last day of October. I thought I would try to squeeze in one more update before November is upon us. The mighty Oak across the street from my apartment is still wearing a full complement of leaves. The rich shade of Amarillo tells me that the mild days are almost over, for now. I'm told that we should expect another snowy winter, albeit one with wider intervalic deliveries. That sounds fine to me. Receiving a foot of snow every few days for 3 weeks got old quickly. Snow or not, there is plenty going on to keep me engaged through the winter, however long it lasts.

I recently joined and glued the plates for the top and back of my mandolin. Though we always work within tight tolerances, some of what we do matters more and standards cannot be successfully compromised. Joinery is the process of preparing a glue joint surface on two or more pieces of wood. In building an arched-top instrument, joining the top and back plates is one of the most critical steps. The joint really needs to be absolutely without gaps and that is easier said than achieved. Patience is sometimes rewarded with more frustration. Or it can yield success, as it did on this night. Both joints were successfully mated and the gluing process went off without a hitch. Dry clamping several times helps the process go well. Here are the plates after gluing. Click on the photo to have a clear view of it.


The top plate is a particularly ringing piece of old-growth Adirondack Spruce. The back plate is highly flamed AAAAA Big Leaf Maple. The Maple arrived from the Pacific Northwest as a billet. I did my first re-saw for the money and got a beautiful bookmatched result.


The rim of the mandolin has already been prepared using a block plane and a flat sanding plate. This ensures that the edges of the ribs are even around the entire shape. The back and top are glued directly to these kerfed edges and so they must also be flattened in order to get a happening glue joint. This process is tedious but absolutely necessary. We start out by flattening the face of the plates on the jointer and quickly move on to using the trusty block plane again. The blade needs to be razor sharp for this to work well. We check flatness with chalk dust spread over a machined flat plate. We spin and turn the wood plate on that dusty flat plate. The chalk dust catches on the high points and then we shave it down, a fraction of a millimeter at a time. Here is the back plate with an accumulation of chalk dust right on the corner.


Once the plates are nice and flat, we get to do some cutting on the band saw. First you have to decide how you want to orient the cutout on the plate. Sometimes there is some extra nice wood figure that you want to preserve on the instrument. Once you are happy with the placement, you line up the center line of the rib structure directly on top of the glue seam. Then, trace around the rib structure using an awl with a nice sharp tip. I filled in the tracing line with some pencil lead to increase visability.


And then, to the saw! You don't want a lot of extra wood on this cutout. We shoot to stay .5 mm away from our line. The pencil lead and a bright work light help a lot. The saw I selected was cutting like a dream and it was a piece of cake to manage a clean cutout.


Thanks, Brian B., for the great saw setup. This is a fun step because the project progresses from being almost "just a board" to looking like part of the whole. This process is repeated for the top plate and then the carving begins! I can't wait to share it with you. This is my favorite part, besides playing a tune. Sharpen those knives!


  1. Points to you for using 'intervalic' in a sentence. Well done. Also well done is your instrument. Coming along nicely, I see.

    Say, how about that price list, if you can get to it, for my Strat upgrade? I know you've got much going on - shoot me an email when you can.

    Love and Sprockets,