Peter Coombe Mandolins and Guitars
The inner border of the groove that the inlay is to fit into is first marked with a sharp pencil in a compass.
Then it is cut with a sharp blade along the pencil line.
Next the outer border is marked using a small jig fitted with two scalpel blades set to the exact width of the groove.
Now the outer border of the groove is cut with a sharp blade.
Here the borders have been cut.
Next the groove is chiseled out with a small chisel.
There is a number of iterations of cutting the border and deepening the groove until it is just deep enough to take the abalone strips. Here I am checking that the groove is deep enough.
I use curved ablam strips for the inlay. You can use real abalone shell, but shell is brittle and must be carefully matched so is much more time consuming. The ablam comes in curved strips designed to be fitted into guitar rosettes, but the curve is not sharp enough for mandolins so need to be cut into short strips of about 10mm each. Each cut strip must then be fitted to the adjacent strip. I use a piece of sandpaper on a flat surface to fit the cut edges together.
Each individual strip is cut to size and fitted to the adjacent strip and so I slowly work around the groove.
Once the centre join is reached, the strip that crosses the join is marked with a pencil along the join so that later it can be positioned correctly. This is the piece that is glued in first.
Here we have all the ablam strips cut to size and fitted together.
Now the ablam strips are removed from the groove and stored on a strip of sticky tape, being careful to keep everything correctly oriented and in order.
Here all the ablam strips have been removed.
On each side of the ablam strip there will be a strip of black/white purphling. This must be bent into shape. First heat the pipe.
Now bend it around the hot pipe.
Here they are bent to shape.
Now fit the purphling into the groove with the position of the ablam taken by a strip of teflon. This is the time to find out if the groove has been cut the correct width. Some additional fine trimming might need to be done now.
For this mandolin all is fine, the purphling and the teflon fitted perfectly so no trimming is required.
It can now all be glued together. I use high strength epoxy glue for this job. 5 minute epoxy cures too fast, it does not give you enough time to get all the pieces of ablam in place before it starts to cure. Glue is first put into the groove and the first ablam strip glued into the groove with the purphling. The first strip to be glued is the piece we marked as going across the centre join. I then work along the groove each side of the centre join.
Here everything has been glued and clamped into place. Not too much clamp pressure here or the purphling will be damaged, just enough to hold it in the groove. This is left at least 24 hours for the glue to cure.
Once the glue has cured the purphling is trimmed with a finger plane.
Then the inlay is sanded flat to the surface of the top. This can take some time because the ablam strips do not always set flush to each other.
Here it has been sanded level to the top.
Next we need to line the soundhole. First a thin strip of Walnut is cut on the bandsaw and thicknessed on the linisher. I use Walnut because it is the easiest timber to bend. I used to use Maple, but it does not bend as easily as Walnut.
Now we heat up the pipe again.
Bending the Walnut around the hot pipe.
Fitting the Walnut into the soundhole.
Trim the Walnut to the correct length. This is not so easy to get right. The Walnut needs to fit snugly into the soundhole.
Glued and clamped.
Once the glue is dry the Walnut soundhole lining is trimmed flush to the top with a fingerplane.
Flip the top over and trim the underside.
Now sand the underside.
A final hand sand and the top is now ready to be graduated and braced.