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Ouch! Help repairing rosette?
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14169		 Page 1 of 1
Author:  Jim Kirby [ Sun Oct 21, 2007 4:51 am ]
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I was cutting soundholes for a set of classical guitars I'm starting. One of the rosettes was odd shaped and was easier to coaxe into a channel that had a smaller than nominal diameter, which means that, unless I made the soundhole smaller, it was going to have a very narrow ring of wood inside the I.D. of the rosette. I didn't want to make the soundhole smaller, so I went for it. Apparently, my possibly-getting-old-and-dull upcut bit didn't agree, and tore up part of the ring of wood (actually, a region on each side of the circle.



I'm wondering how you would go about recovering from this. My idea is to take a small (and newer and sharper ) bit and try to rout a little binding ledge around the hole. The damage only extends down about a mm, so there is clean wood at the bottom to cut the ledge into. Then, bind with light colored purfling strips (maple? holly?) I need to repair the entire width from the inside of the rosette to the soundhole edge.

I'd be glad to hear your alternate suggestions. This is the stiffest top across the grain of any in the batch I'm starting, and there is no way I'm abandoning the top.

An attempt (feeble) at a picture follows. Thanks.

Jim


Author:  Rod True [ Sun Oct 21, 2007 5:19 am ]
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Dang Jim, that's no fun is it.

Well, I have a couple of ideas but I'm not sure if it's the best ones, but I'll give them anyway.

1st, how thick is the top? Can you sand down a 1/2 mm and than round over the edge of the sound hole? This would not require you to make a "plug" to center the rosette on.

2nd, if you do have to make a plug for re-routing purposes, you could flip the top over and install another rosette on the flip side. You'd have a rosette on the inside which you could could cover with a soundhole reenforcement plate like Dave White does and it would cover it. Like this



Check out this page on Dave's website for some other details.

And you might want to use down cut bits for cutting out the sound hole next time
Author:  Rick Turner [ Sun Oct 21, 2007 5:50 am ]
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Cut the sound hole out with a sharp fly cutter.

For the repair, I'd consider removing all the spruce from the sound hole to the inside edge of the rosette, and then you can inlay a plug of spruce, back it up with a thin "donut", and then re-cut the soundhole.   

You could cut the spruce "coaster" plug with a slight taper on the outside edge so it fits nice and tight. Glue it in with HHG, and tap in in place with a soft faced hammer, and you'll have an invisible repair.
Author:  Jim Kirby [ Sun Oct 21, 2007 7:11 am ]
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Rod - top is already down to 2.7mm. If it had been at it's original thickness, I could have sanded the top mm off (original rosette and all) and started over.

Rick - Sounds like a plan, and the design I am working from has a soundhole reinforcement anyway, so there is no problem adding one in. I think I'll give it a shot!   

I should get more proficient with fly cutters. I've used one in someone else's shop but haven't set one up myself.

Jim


Author:  Rick Turner [ Sun Oct 21, 2007 7:30 am ]
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I'm going to make a vacuum chuck drill press table for using flycutters. It can be a bit hairy holding onto a top with one hand while pulling down on the handle with the other!
Author:  Shawn [ Sun Oct 21, 2007 11:06 am ]
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Because the top is at 2.7 you still have plenty of material to work with.  How deep is the rout for the rosette?  How is your rosette area reinforced?  If you are using a "donut" ring of spruce to reinforce the rosette area as opposed to flat braces running towards heel to tail on each of the rosette, you should be able to take down the rosette area and still have material left.  If your rosette is thin (1mm or thinner) then you may not have the ability to thin as you would take away the rosette.


I believe that Rick's idea makes the most sense and in the end will give the cleanest result.
Author:  Rick Turner [ Sun Oct 21, 2007 3:28 pm ]
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Knowing how blow-outs telegraph pretty deep (don't ask...), I would not start sanding planning on success.   You could get down to 2.2 mm, and still have those things going...and then it's what? 1.75 mm? 1.5 mm?   Oh, you're out of top now...
Author:  Jim Kirby [ Sun Oct 21, 2007 9:21 pm ]
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Shawn - No, not enough rosette left there to do something like that. I think Rick's idea is the plan.

Thanks everyone. I'll send pictures!

Jim

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