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removing finish for bridge glueing
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14198		 Page 1 of 1
Author:  TommyC [ Tue Oct 23, 2007 3:55 am ]
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Hello all. I have glued hundreds of bridges onto new guitars while
working at Gibson, MT. They use nitro so it's really easy to scribe around
the pinned in place bridge and use a heat lamp and sharp chisel to peel
off the finish, you don't even have to scrape. I hate working with nitro
and am looking at other more health friendly finishes such as shellac or
Tried and True varnish oil. When using these finishes, is it pretty much
just the same game to remove it from under the bridge footprint? Do oil
finishes soak into the wood making scraping difficult to impossible? I
have used masking tape before but did not love it. It was with a brushed
on water based finish and going over the masking tape created little air
bubbles. It also left this step in the finish that in hindsight was not
terrible but at the time I wasn't comfortable with. For you folks that use
these or similiar finishes what methods do you use? I guess the same
would apply for the fretboard tongue as well.
Author:  TommyC [ Tue Oct 23, 2007 4:33 am ]
Post subject: 
Thanks Hesh. I know that some experimenting is in order but like to get
some ideas before I start. Any varnish users care to chime in?

Hesh, I worked at Gibson for about a year and a half starting in '94 or so. I
have gleaned many tricks and techniques from them but it was such a
production sort of place that most people did not know why they were doing
what they were doing. Still, it was cool, and I did learn alot.
Author:  John How [ Tue Oct 23, 2007 5:08 am ]
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I have tried using masking tape as well but found it gets in the way when doing final leveling and if you take it off before finish sanding I risk getting water (used in final sanding) under he finish causing trouble. So I starting finishing the entire top and then marking and scribing after buffing and use a dremel router to rout the finish off. I put masking tape over the entire bridge area(double thickness), scribe and then peel of the bridge mask leaving the area surrounding it covered. Then about two minute with the dremmel in a router base set to cut just the thickness of the finish, leaves a nice clean gluing surface ready for the bridge.
Author:  Michael Dale Payne [ Tue Oct 23, 2007 6:10 am ]
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I have scarped, masked and routed.

French polish (hand rubbed shellac/PG alcohol): I prefer to lightly tape off the outer perimeter for protection. Then scrape with a single edge razor that I turn a burr on with the outer edges rounded over to prevent gouging.

Nitro and waterborne acrylic lacquers: I like to tape off prior to application then scribe at the tape prior to pealing off the tape after leveling and preliminary buffing.

My bridges have a small .005"deep x .063" wide ledge in the bottom so that my glue surface is an 1/8" less than my actual bridge width and length or 1/16" to the side. This allows the finish to actually be under the bridge 1/16" for a nice clean joint but not interfere with the the glue joint.
Author:  TommyC [ Tue Oct 23, 2007 7:40 am ]
Post subject: 
Thanks Michael. Are the bottom of your bridges radiused to match the top?
I can't think of how you would put that small rabbett on the bottom of the
bridge if it is radiused.
Author:  James Orr [ Tue Oct 23, 2007 10:09 am ]
Post subject: 
When I was with a builder this summer, he'd just gotten a guitar back
from Addam Stark, who had used Frisket Film under the fretboard and
bridge areas. The builder just cut a line around the film with an exacto
and peeled it off.
Author:  L. Presnall [ Tue Oct 23, 2007 10:22 am ]
Post subject: 
[QUOTE=Hesh1956] Hey Tommy having worked at Gibson I'll bet that you could really teach us a thing or two or three.

To answer your question I tape off the bridge area before my guitars are sprayed. Then of course I am simply removing the tape.

But I have also not taped off the bridge and fret board extension areas and used either a small scraper that I made or a very sharp chisel to remove the finish to the scribed line. This was done for French polish and nitro. I have no experience with True oil.

Consider cutting a small ledge around the edges of the bridge and then removing or taping the finish for the bridge foot print to the ledge. This way the bridge is actually sitting on top of the finish where it will show and makes for a very clean installation.[/QUOTE]

I have a question that's I've been pondering since this topic was posted originally back in the day...if we're cutting a ledge around the perimeter of the bridge which will not contact the surface of the top (and thus, the laquer) why not just leave the finish under the bridge say, 1/32" and forego the ledge altogether? Since the glue won't stick well to the finish, cleanup should be a snap and the same amount of bridge would still be glued to the guitar top? Or am I missing something? Speak o wise Hesh!!
Author:  Mattia Valente [ Tue Oct 23, 2007 11:52 am ]
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Someone here (I forget who) mentioned a possible advantage of taping off at least most of the bridge area; thin masking tape is about the same thickness as the finished film you're shooting for, so if it's recessed, it's too thick...
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