Violin Forum/Message Board

[John Cadd]

I had no idea purfling machines were accepted . For any beginners it`s vital to have the wood held securely and only one pass is made without interruptions .Don`t try to stop in the middle of a curve.

[John Cadd]

I can contradict my last statement about stopping in the middle of a curve. The purfling attachment I am using has a flat brass plate screwed to the body with a slot for the cutting blade to poke through.That makes it possible to stop the depth of cut exactly . But there is not enough adjustment possible to get the cutter near the end of that brass plate. The problem comes as you work on the tighter centre curves.The brass plate touches the arching curves and pushes the cutter out of line and tends to scratch the varnish . This repaired violin is already varnished .So the cutter struggles to stay on course and leaves a zigzag cut .Not a disaster as I expected though . After filing the ends of the brass plate I clears the arching and the groove can be cut once more .The inner surface will now be exactly right and even distance from the edge .
But the outer zigzag is still there . The cutter distance from the bearing wheel guide was 4mm. That clearance has to be reduced to make the outer edge of the cut as smooth as the inner edge.The uneven section with then have an even curve and the remaining gap will be simple to fill with a thin strip of spuce. There is still enough outer wood to contain my mistake . This violin has survived bigger disasters and will still have it`s life extended . If I tap on the top and back it`s remarkably resonant .It ought to be , it`s a copy of the Plowden as far a thicknessing goes.
The new ribs I fitted were made to follow the uneven corners between top and back but the curve outlines did not leave ecact overhang edges .I corrected the biggest overhangs and the part on the longest curve where the chinrest fits swerves in a bit. The volume internally will be a bit less but the thicknessing adjustments I did will bring it back to the original volume. It`s starting to look attractive maybe more as a Picasso than a Guarneri .
I made a heavy wooden frame a long time ago to support a violin It has a cuttout for the arching with leather edges to save the varnish . The oblong frame in mahogany is solid and heavy .There are some rotating clamps to hold the violin still .For purfling cuts on the corners the frame can be tilted against the table and sat in my lap. It saves leaning over all the time and I can sit down .
The worst part of purfling is the eight corners . I have a very thin cutter so far unused that will work on the bee sting area . it will need to be freehand as well .I need to practice on some scraps . All the 4 corners had been worn down on the top so they were replaced this week .I was able to compare top to back shapes even though they were quite out of position technically.

[John Cadd]

First tip ; Don`t try to use a machine on the corners. It will never work .
Second tip ; Try to work out if your purfling will break apart when you try to bend it .I must have bought some rubbish.The black strips peeled of in 1/4 inch pieces.If the grain was straight along that would not happen . It was dipped in boiling water before trying .

[John Cadd]

The purfling machine with a brass plate is quite foolproof if the arching shape is prepared for . The centre bouts are the most important to watch out for . The concentration has to be kept on a right angle to a curve. That sounds like a contradiction . Then try to get as close to the corner ends without overshooting . That will minimise the hand cutting of the corners .The best part of a purfling machine is the constant safe depth of cut. I noticed the resistance each time the cutter arrived at the glue joints where the top plate had been repaired so many times . The speed of the cutter blade can be adjusted (not while using ) Any hard glue may overheat at the wrong speed .
Mainly secure the violin before attempting the job .Keep the drill body vertical and hold the roller bearing close to the violin edge and square to the edge line . It`s best to practice any body movements you may make before starting .Think of sky divers on the ground running through the pattern before taking off. You can`t scratch your nose when it starts .
The worst part is getting across the neck join in the back. I was not prepared very well for that gap . Take time to make a template to guide your knife and decide how straight or curved it needs to be . I already had doubled the neck area before I started . It might be better to just leave a gap or make a cheeky ink line without purfling there .