Purfling groove 2 mm, Really! Because we are taught to do so?


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I think we are over working many things. I'm at the beginning of learning this craft and I see a lot of foolish habits in modern making. 

Having tried lots of different methods, I still purfle into a thick edge.

 

I don't see it as a foolish habit, rather a tried and tested technique that gives me the results I want. 

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Note the slight angle at which the purfling has been set in.

 

My purfling can look like that because I don't hold the knife vertically. Sometimes I cut around the plate in the same direction (the trench slopes are parallel) or I cut in the opposite direction (the trench slopes are not parallel).

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hmm the Quote function doesn't seem to work for me.    What would cause the purfling to be at an angle like that?   Maybe an indication of the purfling being put in an already closed box.  The purfling cutter would be held at an angle because the ribs get in the way of the cutter or the makers hand? 

 

 And also interesting is how the grain lines are not vertical...   

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It was suggested to me early on to cut purfling groove by hand and I never have regretted it.  It makes a difference in the finial look.  The slight  irregularities come through in the end and it looks much more interesting to me.  I cut my grooves on a thick plate and it is not really that difficult (unless you are trying to churn em out like a production line where the extra effort and time has some disadvantage)

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You can choose how to do it now, but not how it was done then. 
Looking at old plates you can see how stray knife marks were not 
gouged out after, as is done often today. A bit like inlaying a decorated back. 

I like all of Roger's articles, they hold together like wood and glue.
Perhaps at some point they all come out as a massive hard back book. 

The Betts scan and photo above are very cool. 

I do it like Conor trying to leave plenty wood under the purfling for strength. 
When the corners and button are thicker than the rest of the plate,

the fluting and purfling won't look 'flat' as it can on some plates. 
The purfling depth on the Betts scan looks quite shallow compared to edge thickness.

If your purling knife is sharp and has a rounded end on it, and if you use a little soap 
with repeated cuts, you don't need any strength to cut a groove. 
Melvin, interesting to hear about your Dad.



 

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to follow the protocol as described in Roger's book/articles? yes it does.

 

To follow the protocol as described, yes you will get this result.  If you look at the links I posted earlier you can see I have worked in this direction.

 

The same result can be achieved with almost finished arching/channel and shallow groove. This is the question I ask, not questioning Roger's methods.

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The same result can be achieved with almost finished arching/channel and shallow groove. This is the question I ask, not questioning Roger's methods.

 

I find the deeper purfling groove useful particularly when forming the corners. I find it much easier to make the shape I want, when there's a good depth of wood to support and shape the point . If I make the purflings with three loose strips, this is even more important.

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To follow the protocol as described, yes you will get this result.  If you look at the links I posted earlier you can see I have worked in this direction.

 

The same result can be achieved with almost finished arching/channel and shallow groove. This is the question I ask, not questioning Roger's methods.

I do it the same way as you are suggesting. Actually I was taught this method years ago by Neil Ertz, who worked with Roger in the 1990's

But I think Roger feels that there are certain advantages to his original deep purfling protocol, as described in his articles.

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It seems obvious from the posted CT scans of very old instruments, and descriptions of methods used by modern makers, that the purfling can be set very shallow indeed compared to the finished thickness of the plate. 

 

Wouldn't this suggest that purfling is really decorative and doesn't contribute to any structural stability?

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I find the deeper purfling groove useful particularly when forming the corners. I find it much easier to make the shape I want, when there's a good depth of wood to support and shape the point . If I make the purflings with three loose strips, this is even more important.

 

Three loose strips?

 

I do believe this is the first I've heard of this method.  Do you find it any different/easier/??? than using pre-glued purfling strips?

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It's not easier, except when you're making a complicated design, when it's really the best way, I think.

 

I usually do it this way, because I like to have a little variation in the thickness of the strips, so I cut each one separately. They're very thin and floppy, especially when you add glue, and a good depth of channel makes life easier. 

 

I find that when I make pre-glued purflings they can be quite clean and sterile looking. I'm making a Strad model at the moment however, and I've made up sets of purfling from veneers for that.

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Three loose strips?

 

I do believe this is the first I've heard of this method.  Do you find it any different/easier/??? than using pre-glued purfling strips?

 

The ‘trios brins’ method used by the 19th-century French violin makers.  Frank Ravatin  did a demonstration at the VSA in 2000

 

More can be found http://www.thestrad.com/cpt-latests/7-tips-perfecting-purfling/

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In my workshop cutting the channel, of course there is nothing wrong with a 2 mm deep groove. And it doesn't take long with some small sharp hand gouges to work the channel down to 3,5 mm, working with the wood grain. I think the result is acceptable too. The edges are ~4,5 mm and up to 5 mm in the corners.

 

post-37356-0-34808200-1454760257_thumb.jpgpost-37356-0-28612700-1454760277_thumb.jpg

post-37356-0-97155500-1454760300_thumb.jpgpost-37356-0-57538900-1454762069_thumb.jpg

 

The wood is dry and chippy so it helps moistening the channel with a small brush.

 

Done

 

post-37356-0-52803300-1454764486_thumb.jpgpost-37356-0-98339500-1454764469_thumb.jpg

 

 

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Peter, I think you might want to re-think your channel depth.  Three five is, I believe, a bit thick.  I had one dealer tell me he wanted to see 31 to 3.2 for finished edges.  I think that is a bit thin, 3.5 final edge thickness is what I like, and I think it looks better than a thick heavy edge.  This is just my opinion, so take it for what it's worth. 

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How often does purfling stop a top crack from getting to the edge, and if it can, how much does the purfling depth matter? I have wondered this for awhile, and there are plenty of great restorers here. Please settle this!

Hi Not Telling

From the instruments I see, I'd say that tha front purfling does act as a barrier to cracks. I think it protects the front from damage coming in from the edge when the front gets a knock. And of course it limits wear and tear, and gives you a starting point when you must repair it.

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