Violin Forum/Message Board

[John Cadd]

I thought I bagged a bargain on AliExpress . It was an attachment to hold fine drills to cut out the purfling grooves .One of my least favourite jobs . I have a Dremel drill but the threaded plastic end was too wide to fit the alloy attachment . After a few struggles I filed the plastic thread down and had to tap the new thread slowly working it together and using a diamond triangular file . The alloy left a silvery contact trace each attempt and I finally got the whole thread to fit . A few tests at 2 mm deep was a success .I used it on a straight board along the grain and across the grain . No trouble at all .It has a roller bearing as a guide against the edge. The Bit is about 1.5 mm thick . Purfling fits nicely . The adjuster screws need a Japanese cross head screwdriver to avoid damaging the screws . This attachment only cost about £9 .

[MikeCooper]

Do you cut the full 2mm depth in one pass? I'm afraid of using one of those machines, afraid I might slip and mess up the channel.

[John Cadd]

The question is will the attachment fit the Dremel type machine you have . I thought Dremels were the most likely ones to fit the thread . As is most likely ,whoever we ask there will be no reply . I have used the machine on Pine along the grain and across the grain. It cuts in one go and the purfling fits beautifully . Using both hands with a 1.5 mm bit there is little chance of any kickback . I would get a foot control for security. I don`t know the ideal speed for these .It works at level 6 .the fastest . other bits are thinner . it would allow a central cut which would make hand cutting easier . Certainly it would avoid cutting too deeply . But you need steady nerves to make a violin . Practice on scraps first.

[John Cadd]

I found a Chinese Rotary drill for just over £6. (£20 off ). That is one of the few that have a threaded collar on the body of the drill .It`s a similar layout to Dremel . I will see if that is a more natural fit to the purfling attachment. The drill comes with all the accesories you might ever need .Otherwise file off the Dremel thread and tap on the attachment ,which is a nuisance .
Important point--- There are two designs of the purfling attachment. The more expensive ones are bad for purfling a violin. They are better for guitars . The best violin purfling attachment has a brass plate poking out with a slot for the bits . That gives a solid contact with the violin
surface and limits the reach of the bit .The ones without the brass plate will have no control over the depth . 2 mm depth is what you need .Nothing more than that .
Both models have a roller bearing to ride along the violin edge . The corners have to be cut by hand .No short cuts there .

[John Cadd]

It`s not exactly easy to communicate with AliExpress.I don`t know how to get a question about thread sizes to them. The drill I ordered looks like the DayPlus model .They don`t go in for maker`s names. A similar blue/black model mentions the word Dremel in the blurb so that collar thread will not fit .All I can say is ---Try the blue one .
Prices go up and down like a fiddler`s elbow . The first time I thought the purfling attachment looked really cheap with a picture of the alloy attachment . When the parcel arrived it contained one Dtrill Bit and nothing else .

[John Cadd]

AliExpress sells items at very varied prices. The alloy attachment can be found at over £80 all the way down to about £9 or even £6. Sometimes it`s like throwing mud at a wall .Some of it will stick . So even if the lowest price item is not perfect you might find a slightly better version .Then the postage can also be free .Nobody really loses in a system like that .

[John Cadd]

Pictures of purfling machines with a photo of the electric drill attached are few and far between . Diagrams showing dimensions seem to avoid information about the neck collar . Sometimes theyadvertise --Compatible with Dremels but it`s a guess to believe that . Dremels are too large to fit the attachment so you come back to Making it fit or take a gamble to see if this is the one you have been searching for .

[John Cadd]

I missed part of the meaning in your question about the 2 mm depth .Yes 2 mm is the full depth needed in the final cut .That is done in one go . If you started the purfling channel with the edge thicker you need to think about the wood you leave behind. The final thickness below the cutter tip needs to be 2 mm thick . I have been assuming the edge thickness would be 4 mm thick .
The danger with a hand cut channel using a pointed knife is cutting much too deep . Some violins have the edge breaking off near the chinnrest where the purfling knife has cut almost right through . Leave 2 mm of wood intact all round the edge .

[John Cadd]

I tracked down one brand of "Dremel type" drill shown on AliExpress which is shown with the Purfling attachment fitted . The current price for that drill is £4.30 . It may work or it might be rubbish . But asking one seller about a similar drill with a screw on collar was a waste of time . They only described the collet size as 1/8th inch .Somebody behind a desk that knows nothing more than they have to .But I saw one with the attachment fitted . Result .

[John Cadd]

I tried to find another drill to work the purfling attachment.It has a threaded collar .But that is far too narrow to fit the attachment. It will be good enough to make small holes for screws .
So far I have used a Dremel by adapting the plastic collar to fit the alloy thread . I bought a rechargable drill that was too small and the switching positions are bizarre .You have to work through 3 speeds to switch off . So I tried another small mains drill which is much easier to manage . I used the tiny drill supplied to cut out the lining pockets in the C bouts . That was a lot safer than trying a Purfling cutter with a sharp edge . I stabbed my finger with that one . This latest drill could be adapted to use a purfling attachment . Car body filler resin could be used on the drill collar and the alloy attachment . That would be a permanent fixture at a very friendly price .Just clamp it all still at 90 degrees for a few hours . The collar on this drill was not threaded .It just had a series of ridges.

[catbrain]

John-----
I tried the dremel on my first top. It worked but I have one little spot where it slipped and made a small round bump. i didnt do it that way again. I had made a "block" that screwed into the end of the dremel--- and the block had a guide pin that could rub on the outboard edge of the wood.

After that --- I designed a too that holds two mini-razor knife blades and has a similar guide finger. It works great and doesnt have the stress level involved with the dremel. The blades are stacked with a steel shim in between to set the groove width.

Tim

[catbrain]

the guitar makers have units which are designed to screw on the end of dremels and cut purfling grooves. Stewart McDonald has them--- just google and you will see it......
look slike just what you want------

[John Cadd]

I used the dremel for a short strip where the edge had been broken off. I had planed a straight line and eliminated some original purfling . So I cut a groove to match the two stopped ends . I had no trouble getting the line to match . But the purfling is black /white /black . I only have white /black/ white but it`s very cheap to buy . I put a strip in dry and taped it over till I get the right stuff .
I don`t know how long the cutter will last in Maple . I`ve only used it on softer wood so far .
Thanks for the guitar tip .

[Rick M]

There’s a good thread on here about this. Couldn’t recall how to include the link but it’s titled “cutting the purfling channel” there are a couple of photos of the home made rig that used using dremel and cnc bits. Plus lots of other discussion

[Michael Darnton]

https://darntonviolins.com/purfling-machine-eight-views/
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