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I've searched the archives to no avail, for someway besides free-hand for cutting shell rosette strips. The id is a no brainer by grinding on a desired diameter wheel but I'd like to have something dependable, repeatable, and adjustable for parallel od pieces. Anyone have a plan, idea, or picture they'd like to share?
thanks,
Tom Armstrong

Tom,
Here are some pics from Amy Hopkins class at ASIA last June. I've never made this jig, but it looks very useful. Enjoy!



Tracy

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Tracy
http://www.luthiersuppliers.com

Lance has a really cool jig he made up. Somewhere there is a video of it. I will dig a little, or perhaps he can just post a link.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

HERE is my jig.

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Lance@LuthiersForum.com

If you are looking to make curved pieces for rosettes, after grinding or sanding the inside diameter, make up two discs from MDF or ply that are the same diameter as the desired outside diameter of the shell ring. On one disc, make a small ledge with the same inside diameter as the shell ring. It helps to pad the bottom of this ledge with some thin cork. The depth of the ledge should allow the cork/shell sandwich to sit slightly proud of the top of the disc. The second disc is then used to clamp the shell in place and the outside diameter of the shell is sanded on a disc sander using the wooden disc as a guide

Thanks for the tips so far.
I should have explained a little better that I am looking to make curved strips. Like I said in the original post, the inside diameter is not a challenge, it is keeping the outside to a precise arc and parallel to the inside diameter. I've not used shell in rosettes before and maybe I'm making this more complicated than it really is???

I dont have a pic handy, but I use a 5 inch fine grinding wheel to create the inside curve, then mark and cut by jewelers saw the outer curve rough, and oversize a bit. I then made a rotating vise that holds the shell piece in a little slot that is also cut at a five inch diamter, and clamp the base of this on the table of my sanding wheel, then simple adjust to teh right arc and sand each piece - i can make enough for a rosette in 15-20 minutes. Whats nice is I can use any shell type, and make virtually any width I want. The 5 inch inner diameter will work with almost any rosette pattern/size you will encounter. If I need smaller, say for a 3.5 inch soundhole, I sand the shells inner edge on a 4 inch drum/sandpaper first, and have a different arc setting for the clamp to sand the outer edge.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tom,

I used jigs out of Campianos book. My rosette inlay is made up if sections
cut from 25mm square pieces of abalone. I first sand the inner curve on
the piece on a 50mm sanding drum in the drill press. I then hand cut
outside radius with jewellers saw. I then mount the piece in a pivoting
arm that swings in a radius equal to outside radius of the inlay. I swing
the piece past the sanding drum untill close to final radius. Final
trimming gets done by hand with a sanding board.

I also do a full mock up rossette in channels cut into a polyurethane
chopping board. Once everything is ready to go I set the router up using
the chopping board channels as a guide.

Tony and Martin,
Sounds as though your process of a pivoting vise against a fixed grinder is similar to what I had in mind. If you know a source for a picture it would be helpful, if not, your advice validates what I was thinking....thanks.

Tom, do you have the C&N book (Cumpiano & Natleson) -- the jig Tony describes is illustrated there.

jsut took the pic this morning - here it is. Notice I have used both ends, one gives the std 5 inch radius to the inner curve of the shell, the other is 4 inch. Using a circle cutter jig I routed the ledge that the shell sits in - about 40 thou deep to hold 50 thou thick shell. The wood is afr blkwood, so it holds a thread well, the clamp bar is a pc of aluminum with a couple small pieces of veneer CAd on at each end - they allow the alum to sit just above the blkwood, and give the screw some ability to apply pressure on the shell piece. SImply clamp up to the sanding disc, set for whatever width of shell you are after and pivot/sand away.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Thanks guys....got it!

Tony "the Grizzled Veteran", I like yours better than the one in the C&N book.