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PostPosted: Sun Feb 25, 2018 7:59 pm 
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Koa
Koa

Joined: Sun Sep 16, 2007 1:27 pm
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Location: United States
After fifty or so guitars I still struggle with a clean edge around the bridge.

So, what do you recommend?

My current process is to tape off the approximate shape and location of the bridge, then spray nitro.
Once ready, I remove the tape and scribe a line with an exacto blade and try to remove the rest of the lacquer.
Something ALWAYS goes wrong and looks wonky.

Please give your tips/tricks

Thanks
Dave


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PostPosted: Sun Feb 25, 2018 8:09 pm 
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Cocobolo
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First name: Andy
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If shooting nitro, it is a thin finish. Locate and set the bridge. Tape along the outside bridge perimeter so you know the actual size. Remove the bridge. Now tape about 1/8" or so inside - this is the bridge patch. Remove the outside perimeter tape. You now have an effective bridge patch area taped. Spray.

Once finish is set, lightly score finish along edge of tape and remove tape at patch area. When installing bridge, gently sand edge of finish at the bridge patch edge (just in case there is any raised finish along where the tape line was.) Chamfer the bridge edge (say 20 degree angle off flat) with a razor ... just several scrapes. Nitro is a thin finish so a light chamfer is sufficient. The bridge will glue down flat without the finish pushing against the bridge. The finish obviously goes under the bridge, so it looks perfect. Hope this helps. It's actually a very easy process.

Andy



These users thanked the author AndyB for the post (total 2): Barry Daniels (Mon Feb 26, 2018 12:35 am) • Dave Livermore (Sun Feb 25, 2018 10:01 pm)
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PostPosted: Sun Feb 25, 2018 9:40 pm 
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Location: Cobourg ON
First name: Steve
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I just tried this and it worked really well, but it was for french polishing, so I don’t know if it translates.

Unfinished body. Uncarved neck, but it’s fitted to the body. Place the bridge and drill locating holes.

Remove bridge, place Frisket on top of guitar, replace bridge, and cut around bridge with scalpel.

Remove Frisket scrap. The exact bridge area is now covered with .02 plastic.

Finish, remove Frisket, and glue on bridge.

Steve


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PostPosted: Sun Feb 25, 2018 9:44 pm 
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Koa
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I just spray finish and then when ready to set the bridge, hold it in place and score around it with an exacto knife. Use an artist brush with paint stripper right up to the score line. Let it dry and scrape it off with a razor blade. Done.



These users thanked the author Glen H for the post (total 2): pat macaluso (Sun Feb 25, 2018 11:41 pm) • Dave Livermore (Sun Feb 25, 2018 10:01 pm)
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PostPosted: Sun Feb 25, 2018 9:49 pm 
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Sorry, that’s .002 plastic.

Steve


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PostPosted: Sun Feb 25, 2018 10:42 pm 
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Glen H wrote:
I just spray finish and then when ready to set the bridge, hold it in place and score around it with an exacto knife. Use an artist brush with paint stripper right up to the score line. Let it dry and scrape it off with a razor blade. Done.


Same here.


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PostPosted: Mon Feb 26, 2018 12:48 am 
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Koa
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Location: The Woodlands, Texas
First name: Barry
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AndyB wrote:
When installing bridge, gently sand edge of finish at the bridge patch edge (just in case there is any raised finish along where the tape line was.) Chamfer the bridge edge (say 20 degree angle off flat) with a razor ... just several scrapes. Nitro is a thin finish so a light chamfer is sufficient. The bridge will glue down flat without the finish pushing against the bridge.


That could possibly reduce some of the stress risers that are inherent to the more normal squared rabbet approach for insetting a bridge footprint. And that's usually a good thing in a highly stressed area.


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PostPosted: Mon Feb 26, 2018 9:18 am 
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Brazilian Rosewood
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Lots of good techniques here. I think the key is always to finish slightly inside the foot print and then work your way back. When I started I would try and tape off perfectly and there is always a little ridge of thicker finish where the tape edge is so I now do what Andy suggested and come 1/8th inch in. What I do differently then what has been mentioned so far is I first lay down tape on the unfinished top big enough to cover the bridge. Then I hold the bridge in place and score a line in the tape to the exact bridge foot print. Then I remove the outside tape which leaves the foot print in place. Then I come in and remove about 1/8th inch around it and finish the guitar.

Always always always be very careful not to scratch into the spruce (and especially cedar) top when using the razor knife. You just want enough pressure to cut the tape.


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PostPosted: Mon Feb 26, 2018 11:53 am 
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Cocobolo
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Razor blade.


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PostPosted: Mon Feb 26, 2018 12:10 pm 
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I have been shooting the whole top and setting the bridge afterwards.
I set the bridge and tape off around it then come back and score my gluing perimeter 1/16" inside the tape line. I then use a soldering iron with a chisel tip to quickly burn off the bulk of the laquer getting as close as possible to the scored line. A steady, quick hand helps. The perimeter chips off easily to the score line. Then I scrape inside the footprint with a razor blade to clean up any residual.


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PostPosted: Mon Feb 26, 2018 8:39 pm 
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Cocobolo
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I've done the scoring and scraping before many times but switched to frisket film about 10 guitars ago and really like it a lot. I finish sand and fit the neck and position the bridge. The bridge I have partially drilled the pin holes but have not gone all the way through yet. With the bridge in position I drill small locating pin holes through the bottom of the outside pin holes and into the top, but again not all the way through I use plastic side dot rods for the locating rod. Remove the bridge and put down the frisket film over the bridge area. Put the bridge back in place with the locating pins in the holes, they poke right through the film easily. Then with a brand new exact blade score the film, at a slight angle so it is scored just under the edge of the bridge. Remove the scrap and the bridge. Apply, level and buff the finish. Then pry up the edge of the film with a razor blade and peel the film and finish off. the film comes up cleanly leaving a perfect outline. Put the bridge back in place and I have yet to have a bad fit, no finish trapped under the bridge to hinder glue up, and so far no spots showing that aren't covered in finish.

YMMV, but I hope not,
Kent


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PostPosted: Tue Feb 27, 2018 12:21 am 
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Cocobolo
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Plenty of good suggestions here. The bottom line is that the finish is so thin that there’s no need to go crazy getting every last square inch of glue area covered. I’d feel confident with 1/8” under the size of the bridge masked off. Spray, surface prep with acetone to be safe and clamp it up as hard as the wood can take it for 24 hours.


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PostPosted: Wed Feb 28, 2018 1:09 pm 
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First name: colin
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Sorry, bit late to the party, but had a bridge to fit today.
Chisel, 6mm, sharp, freshly, scary.
Attachment:
DSCN0960.JPG

Remove Friskit film (fitted 1/8" inside bridge footprint) and then finish to 0.8mm inside outline of bridge. light sand 240.
Attachment:
DSCN0953.JPG

Rebate bridge to finish thickness + 1 thou or so, after scraping/light sand 240
Attachment:
DSCN0955.JPG

Keeps it pretty tidy.
Attachment:
DSCN0956.JPG


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“There are two men inside the artist, the poet and the craftsman. One is born a poet. One becomes a craftsman.” - Emile Zola


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PostPosted: Thu Mar 01, 2018 10:32 pm 
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First name: Chuck
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I glue the bridge before spraying.


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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins



These users thanked the author ChuckH for the post: Colin North (Fri Mar 02, 2018 5:34 am)
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