Before I started this project, I thought a millimetre was very small – it turns out a millimetre is loads. The top provided with the kit needs to be carved to it’s final shape and dimensions, graduating smoothly from something like 5mm in the centre to less than 3mm thick around the edges. I spent quite a bit of time trying to figure out how best to do this: the only experience I’ve got of carving anything is whittling some sticks with a pen knife.
I think Stew Mac have changed the pre-carved tops they supply in these kits: mine did not look like the ones in the MacRostie video, my top and back appeared more finished than those shown in the film. With a straight edge, I could see that the recurve was already established around the rim, and the scroll was already shaped a good deal. I decided that the only thing I would do to the outside of the top would be to sand it, and do all the carving down to the right thickness from the inside. I bought the two most expensive tools so far: a micrometer, for measuring thicknesses to 1/100 mm, and a beautiful little Ibex finger plane for carving. I bought the 10mm plane, but if you’ve enough money buy the 18mm one as well.
With the outside of the top sanded more or less to finish, I marked out the contours on the top, and took some initial measurements: the top was more or less 5mm thick all over, which meant wood needed to removed as we moved towards the outside of the top from the centre.
I was pretty nervous starting to carve the inside, but in fact carving the top was one of the most enjoyable jobs on the mandolin so far. It took ages to get the knack of the thumb plane, which kept clogging with wood, and I had to keep stopping and unclogging it almost every stroke. After an hour or so, something clicked, and I’ve not had to unclog it since. You need to pay attention to the direction of the grain when carving: if you try carving against the grain, the plane will chatter across the wood, which will tear a little. As I got to know the wood better, I found it easier to know which way to carve. You need to mark the inside of the kerfing from the sides onto the top: beyond that point you want a flush surface for gluing to the sides, so you need to avoid cutting beyond that point.
As the carving progressed, I began measuring the thickness of the wood more often and eventually started to mark areas that needed more – or no more – carving. Holding the spruce up to a strong light was also helpful in identifying thicker areas. At the beginning of the carving, no light came through the wood at all, but when the top was finished, a warm orange glow spread out from the centre of the wood to a bright strip that ran all the way around the rim. You can see markings on the wood here showing areas to carve, and areas to avoid.
I have no idea how much difference it makes to the sound of a mandolin if the wood is, say 0.5 mm too thick. Does it make any difference at all? Does it kill the sound dead? I have no idea. In the end I left the wood ‘on the thicker side’ anticipating further sanding as the mandolin progresses. I’d rather have a mandolin that has a slightly too thick top, than a mandolin that folds in half when I string it up for the first time.
Flushed with the successful carving, I went ahead and cut out the slot for the scroll in the top. Did you spot the mistake there? Neither did I. I merrily cut around the scroll on the top with a coping saw, and filed it out to a smooth curve of about the right thickness. Looks great. It wasn’t until the ext day that I thought to myself ‘hang on, how do I know if that slot is in the right place’ and when I checked, the slot dives much too deeply towards the body. This led to some real consternation: I’d put quite a bit of time into the top now, and didn’t really want to start again: in the end this made me think very carefully about exactly how this would all go together: where the top would sit on the body, where the 15th fret crosspiece would go, exactly how and where the binding would fit around the scroll and what I could do to try and mitigte the error. This planning has turned out to be very useful, and in some ways now I’m glad it happened: it isn’t a disaster, the untrained eye will never notice.