Purfling is not a swear word, its the line around the edge of the cello back and front. Its made of a wood sandwitch traditionally maple, pearwood or beech. Its got to be dense but have flexibility. It also has to take black dye evenly. I made my purfling in the same way as shown on the link.
I’m ready to prepare the edges of the cello. These have to be the exact size relative to the sides of the cello. I marked this out on a previous blog entry. See the pic below to see the edges being finished. I used a variety of tools depending on the lay of the grain and the curve I was working on. These could be files, spokeshaves or mini planes.
After the edges are finished its time to mark out the outside edge of the purfling channel. I use a cutting gauge. see the pic below.
You can see how it is used following the outside edge of the cello back. This is why the back needs to be accurately shaped.
The cello back will eventually have a line all the way around for the outside edge of the purfling.
The distance from the edge is important for the correct formation of the bee sting points at the C bout corners. The cutter on the gauge needs to be turned around so that the flat edge is on the inside of the groove.
The thickness of the purfling varies slightly but it is more or less within 1.6 and 1.68mm. The width of the groove must accomodate this. It can afford to be a sliding fit as the glue swells the purfling to take up gaps. In the picture my caliper battery is low and the readout was flashing so I kept missing the image with the digital camera (pah!).
Removing the pwaste from the groove is done first by cutting deeper with a knife and chiseling out with a special tool made for the job. The knife blade has to be slim so that the edges of the groove are not deformed.
Now that we are ready its time to bend and cut the purfling to fit the groove. I used the same bending iron as in the second blog to bend the strips of purfling pretty much in the same way. The ends are trimmed to give a bee sting shape in the corners.
Once it all fits its time to heat the glue. When I put purfling in I use sightly thinner glue so that it soaks up into the grain of the maple and the purfling. It also swells the purfling and channel giving a tighter fit.
I do the C bouts first and then either end. I use a pin hammer to ensure it goes right down into the groove and that the excess glue is forced out.
Once its all in it should sit a little proud of the surface. This is trimmed back and levelled later on when the edges are properly shaped.
I shaved back one corner for you to see.
Next entry will be doing the edges, finishing the surfaces and contours then graduating the back plate.
Bye for now!
-- Dave D