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Purfling carving tips?


Crimson0087

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So I'm at the stage of carving purfling chanel. Anyone ever use a Dremel with this tool? I think I'm too scared to put a spinning blade of death near something I've worked so hard on. Anyway my first attempt I used this tool pictured to mark the purfling and I ended up with a Chanel too large. I think the blades aren't spaced appropriately. Do y'all recommend I sand them down to bring the points closer together or should I raise one and mark one side of the Chanel at a time? Suggestions? Or should I take my chances with the stew Mac tool?

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I used the dremel tool. Spend time practicing on scrap wood until you have the depth correct. Also, I always held the top or back down to the bench with my left hand, and pushed the dremel tool away from my body. This keeps the tool pulling in toward the plate. If you pull it in toward you, the tool can pull out to the edge..

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I use the brass tool pictured and had to make major modification to the tips of the blades.  I'll show pictures tomorrow but can give a description for now.  When I got it from amazon the blades were sharpened to a needle like tip. They needed to be ground down so that one side is flat and one side beveled.  Like a single bevel knife,  Think chisel, flat on one side bevel on the other.  After reshaping the blades the channels came out just right. 

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Actually I can post a picture now since I woke up and can't get back to sleep so I dug through my pictures here and found it.

See how I slightly rounded the tips rather than the needle sharp points that they originally had. It came with four blades and I lost one. :(

As I recall I placed them so both bevels were facing the same direction to get the right width for the channel but I'm not sure if I remember correctly, It may have been both bevels facing in.  Of course if both bevels face out then there is no distance between the points so I couldn't have had them oriented that way.  

Use them just for initial marking not cutting full depth, use a knife for full depth cuts. I used an exacto but that's probably not the best knife to use since the tip is so thin and it can too easily follow grain lines especially in spruce. I think a small curved blade with a stouter tip would work better for that so I may have to order some tool steel and make one. 

blades.jpg

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7 hours ago, Crimson0087 said:

I think the blades aren't spaced appropriately. Do y'all recommend I sand them down to bring the points closer together or should I raise one and mark one side of the Chanel at a time? Suggestions? Or should I take my chances with the stew Mac tool?

If you want to use both blades at the same time (like I do) you need to thin yours so you can space them correctly, or find thinner ones, such as modifying spare blades for cutters (about 0.7/0.6 mm thick). In the photos you can see what I use and how the blades are shaped and sharpened.

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1 hour ago, nathan slobodkin said:

David, Are you cutting full depth with the gauge or just marking?

No, but I make quite deep traces, then cut to the final depth with the knife. Keep in mind that I purfle with the channel already done, I only need to go 1.5mm deep at most (less for the inside cut). If you look carefully, the tips of my blades are also set to different levels to match the slope of the channel.

Oops, realized the question was meant for another David. Read too quickly, sorry

Edited by Davide Sora
Question not directed at me
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58 minutes ago, J.DiLisio said:

The dremel guide works well and is fairly easy to use but I would caution that it results in a channel with a machined look that is inappropriate for copying certain makers. 

Even to produce modern instruments, showing one's mistakes and imperfections is part of the future personality of our violins.:)

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I've used a bunch of things, what I do now is more or less like what Davide is using. I like rib-backed bard parker scalpel blades for finishing, especially the corners. The type of double bladed marker, set up with blades shaped like Davide's, makes laying out your groove rather easy, quick, and repeatable on a free plate or closed box. 

I will admit that the Dremel rig (I found i had to modify the radius of the guide portion, making it smaller, to fit my upper inner c bout curve) is nice in maple, but barely saves you any time in spruce which is so soft and easy to groove. If you use a rather smaller bit than your intended purfling, and make your purfling yourself, you can then open it with a knife and get good variation like you might see in rougher styles. If you're going after a more exacting style, don't feel bad about machining the groove entirely aside from the corners. 

 

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7 hours ago, nathan slobodkin said:

David, Are you cutting full depth with the gauge or just marking?

I'm cutting to full depth. Jabbing the cutting blade into a bar of soap periodically helps a lot.

The photo below illustrates the setup. Note the shim clamped against the cutting blade, between the edge guide and the blade, which can be adjusted vertically (separately from the blade) to control the final depth of cut.

(Confession: This is not the cutter I actually use any more. The one I use now has the handle below the plate rather than above, more like the one HoGo illustrated, but it's apart for further tweaking and re-designing right now)

purfling2.jpg

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3 minutes ago, David Burgess said:

Too many darned David(e)s! Really confusing. But I had the name before you did, so it is you who will need to choose a new name. :lol:

I know, you are pretty old, and your brass purfling cutter betrays your age. I have one like it somewhere too, but when I bought it I was basically still in the diaper...:lol:

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2 hours ago, Rico Suave said:

 

It is said that an expert Luthier makes no mistakes, but a Master Luthier knows how to hide one's mistakes.  ;)

I would rather say that a master luthier knows the value of his mistakes. ;)

Or rather, he knows when a mistake is a mistake (therefore unacceptable), or when it is an authentic trace of his work that bears witness to a work made by his hands with traditional tools.

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8 hours ago, Davide Sora said:

I would rather say that a master luthier knows the value of his mistakes. ;)

Or rather, he knows when a mistake is a mistake (therefore unacceptable), or when it is an authentic trace of his work that bears witness to a work made by his hands with traditional tools.

Well, it is an old, oft used American (or English?) quip for any Craftsman...

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8 hours ago, Davide Sora said:

I would rather say that a master luthier knows the value of his mistakes. ;)

Or rather, he knows when a mistake is a mistake (therefore unacceptable), or when it is an authentic trace of his work that bears witness to a work made by his hands with traditional tools.

Agreed. I think it's a mistake to not incorporate ones personal working style and methods into the final product. Without that, it might as well be just another factory fiddle.

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3 minutes ago, David Burgess said:

Agreed. I think it's a mistake to not incorporate ones personal working style and methods into the final product. Without that, it might as well be just another factory fiddle.

Thirded. There is a boatload of sterile work out there from the cheap to the eye wateringly spendy, but regardless of price it's very uninteresting. All it takes is a glance at the most beloved instruments of antiquity and today to see that laser precision is not equal to tonal/performance excellence. 

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