Official Luthiers Forum!

It's something I wrestle with on every build and I always think there must be a better way. I apply a gloss lacquer finish to my guitars. Before spraying, I mask off the bridge area, except for a 2-3mm border around the edge. I spray, level, buff with the tape in place. Scribe masked area with X-acto knife and remove tape. Put bridge in place and scribe the lacquer around the bridge with Xacto. Then, carefully, oh soooo carefully, scrape the 2-3mm lacquer boundary up to the scribe mark with a sharp chisel to expose wood and allow bridge to sit properly on the top for gluing (where the base had earlier been perfectly fitted).

This whole business of scraping the lacquer off is frought with potential hazards: it's tedious as hell, lacquer can chip off outside the scribe line, and an oops can occur so easily!! Is there a better way that gives excellent results (clean, no damage to lacquer outside of bridge) and leaves a good surface for gluing?

Other ideas I've seen:
1. Rout a rabbet around the bottom edge of the bridge to "clear" the 2-3mm lacquer border and don't scrape at all -- reduces gluing area and difficult to get the depth just right for a perfect fit against the lacquer.
2. Single layer tape over entire bridge area; scribe tape around bridge and remove mask from under bridge; use Dremel with base to clean off the lacquer and prepare top surface under entire bridge area (saw this in a Tim McKnight build photo sequence).
3. Don't mask the bridge contact area at all, just glue straight to lacquer (like I'm really comfortable with that idea, but I know it's done).

So, anyone got this licked, with a fool-proof, perfect finish everytime, with no "oops!"? Care to share?

No foolproof methods from me, but you should add to your list another common alternative: No masking, apply finish, level and buff, scribe around bridge, remove all finish from under bridge area, glue.
I tried masking and it was more trouble than I thought it was worth, for me. Scraping around the edges is the tricky part and that job still had to be done.

Cheers
John

im no pro. in fact, ive only built one and a half guitars. theres my disclaimer.

i did something similar to your first option. i built a little jig that has the same radius as the dome of my top. i then attached the adjustable roller guide that came with my bosch colt laminate trimmer to said jig. it takes a little adjusting and practicing on scrap to get the rabbet just right, but the result is pretty flawless. i did, however, finish the entire top and then scraped up to the narrow border that the rabbet lays over. next time i think ill mask.

if my explanation isnt clear enough, maybe i can shoot a photo or two. in fact, now that i think about it, i think there is something in the archives about that method. i know i didnt come up with it all on my own. let me know.

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sweat the small stuff.

So, is that the consensus on the preferred method of preping the bridge glueing surface? Todd's method of routing a rabbet around the edge of the bridge to avoid having to scrape/peel/rout the lacquer close to the edge? Or do most scrape right to the outer edge, like John?

Surely there are other opinions on this, as EVERYONE has to deal with this step!

Tim

All I know is that 15 years ago, my son's new Larivee bridge pulled up. It was glued directly to the lacqeur. Gluing over lacqeur probably takes some special preparation to work correctly.

This hobby/addiction/occupation/profession is the classic: 'Two people, three opinions' sort of place !!

Cheers
John

I finish the entire top of the guitar, sand and buff. Put down two layers of the wide blue masking tape, locate the bridge, drill the two outside bridge pins as locators, pin it in place and using a new x-acto blade, scribe around it. Then with a 1/8" carbide spiral bit I rout off the finish to about a 32nd" inside the line. Then I take a 1/4" or so sharp chisel and scraping away from the line, get that last little bit that really just falls off. I have done about 90 guitars using this method and have never gone outside the line or had a bridge pop off. You get a clean wood to wood joint every time and I don't have to worry about any contaminations. The trick is to lower the cutter very slowly until you are just routing off the finish. Make sure that your dremel base is clean and smooth though.

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Tickle your guitar daily, and it'll tickle you back.

You're right, John, but I was really hoping to be inspired by someone's genius on this topic. Like you, I've been scribing the edge of the bridge and then scraping carefully to the line. But it drives me nuts, and I had an "oops" moment last week that had me fuming. Lacquer is repairable, but my repair is not as perfect as I would like.

Heading towards Todd's rabbet method, I've just tried out a mini-router table made for my Dewalt laminate trimmer. Made a new base of 1/4" phenolic. Drilled a notch near the edge of a 50-cent piece, then epoxied it to a 2-dollor coin. 2 screws hold the coins on to the phenolic, with a 1/8" bit sneaking into the notch of the 50-cent coin. One of the screws in the coins is through a slotted hole so I can adjust the width of the rabbet. The round edge of the 2-dollar coin serves to index the rabbet on an uneven bridge edge and the "table" (held in a mechanic's vise) is small enough that it doesn't notice the dome on the bottom of the bridge. Seems to cut a very clean shallow rabbet, so maybe I'll use this to try Todd's method this afternoon.

Cost me $2.50 New Zealand (US$1.80).

Oops, another "John". The method you're describing sounds identical to what I saw in Tim McKnight's build sequence. It's that last 1/32" that is driving me crazy. Maybe with 90 guitars under my belt, I'd be much better at it, but in the meantime, I'm fighting failing eyesight and ageing hands!

Have I had some lifts on client guitars? You bet! I've evolved into deciding the bridge and top radius must exactly match, there should be only a micro edge of finish under the bridge but a little ledge should still be routed for insurance, and the bridge should be clamped with at least three clamps. One or two in the middle on a well fitting caul and one on each wing. Complete removal of finish and shellac if present is a given. I think most of the unexpected lifts I've had could be traced to a missed edge of finish-usually on a wing, or uneven clamping pressure. Oh yeah, use enough glue so there is generous squeeze out all around. Seems like the raw spruce can absorb quite a bit of glue.
The first three kit guitars I built in the late 90's had the finish removed right to the bridge outline, were not radiused for the top, and were glued with plenty of Tightbond with four clamps. Those guitars have not been well treated and the bridges never budged!

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I made my router table platform out of three layers of 1/8" MDF. I glued up the layers in a 25' radius dish using my go-bar deck.

On the guitar I'm building at present, I used frisket film to mask off the bridge area and, after spraying and curing, levelled and buffed pretending it wasn't there. After much deliberation, the option of not masking, but routing off the finish in the bridge area came in as "plan B", although I now have thoughts of trying this approach on my next instrument. The one precaution I might take prior to finishing is to lightly mark the top in the area of the bridge with pencil to more easily judge when I'm through the finish and at wood level; on an earlier guitar, I found it difficult to be certain whether the shavings were finish material or spruce fibres.

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Cheers
Pete

Lots of ways to skin a cat but here is my method:
1 - Spray & buff
2 - Locate bridge after neck is glued on. If you do it in the white then after the finish is on it won't be as accurate due to a few mills of finish under neck heel cheeks.
3 - Mask bridge area off with 2 layers of blue tape
4 - Locate & square bridge to neck centerline. Drill E holes. Hold in place with pins or bolts
5 - Scribe perimeter with a scalpel & remove tape under bridge
6 - Rout finsh off up to tape / scribe line using 1/8" bit and lam trimmer or Dremmel
7 - Scrape corners clean with wood chisel, lightly sand with 180
8 - Remove tape
9 - Glue bridge
10 - Allow 24 hours cure time, string her up and then enjoy.

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tim...
http://www.mcknightguitars.com

Here's the way I've been doing it forever. I'm not saying its the most efficient but it has worked well over the years.
For a pin bridge, top completely finished no masking:
-position bridge, tape in place
-mark outer pin holes using appropriately sized brad point through bridge holes
-take bridge off,drill top
-insert pins into bridge (ream to completely seat) put bridge in place
-lightly scribe (carefully) around bridge
-remove bridge and apply masking tape (2 LAYERS) around scribe line
-Make full size cardboard mask for top with opening at bridge area, tape onto previously applied tape.
-Using small flat artist brush apply Zip-Strip (Stripeeze) carefully just UP TO tape edge.
-Allow time to soften finish carefully scrape off finish with 1/2 wide chisel used in scraper fashion.
-Fold 100 grit paper into 1/2" wide piece trim edges to sharp corner-Sand up to tape
-remove mask, tape and glue bridge.

Process is the same for classicals except locator pins are used through the bottom of the saddle slot.

Thanks for joining in on this, Tim. Your description confirms everything I saw in a photo sequence of your method. One thing I might clarify, is that build my SS guitars on a solera with a Spanish heel, so the neck is attached when I locate and fit my bridge in the white.

As you said, many ways to skin a cat, and obviously your method is working fine with little chance on an "oops" moment. But, I'm still hesitant to clean up a glueing surface with a router. I just have this feeling that prepping the top and profiling the bridge BEFORE finishing, has got to give me the best possible surface for a joint. So I like to mask off most of it to preserve in that perfect condition. Then, after removing the mask, I've only got the laquer left around the edge to contend with. Your system could still work there.

Likewise, I don't like the idea of trying to scrape or dissolve "most" of the finish off a top bridge area, as it can't possibly leave a fresh, uncontaminated glueing surface. But, as David described, people do it and it works.

I've used pretty much the exact same method as John How described since day one and have never had a problem. The real key is to scribe to the perfect depth. Too shallow and you risk pulling up finish beyond your scribe line. Too deep and you weaken the top and risk shearing, especially with cedar or redwood.

As for gluing, I've often thought that one of the main reasons for bridge failure is a glue line that is too thick but not just because of poor fit or poor clamping. I've noticed that with PVA, the edges seem to seal up before all the glue can squeeze out. Even worse with hide glue. Ever notice when cleaning up squeeze out that, as you wipe with a damp cloth, more and more glue keeps coming out? Seems like wetting the glue line reduces the viscosity and allows more glue to keep coming out. That same glue would otherwise be sitting in there making for a thick glue line.

Just a theory but it's worked well for me. No failures in 16 years.

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http://www.chassonguitars.com

After scoring, I've been slicing the finish off with a chisel rather than scraping. It's faster and lots more fun. The key for me is to use a very thin, long paring chisel--the kind that used to come from Sheffield--and to get it really sharp.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

What Howard said. I'm not sure why it's so much fun to start cutting across the top of a brand new guitar, probably some sort of latent sadistic thing. It's even more fun with French polish.

I mask and scribe like alot of people have described. The I scrape the finish off with a heated chisel. About once a year I decide it would be easier to mask the top before finishing. I do that and then go back to scrapeing the finish off. I sand the bridge and top with 120 grit for "teeth". I know there's alot of arguements against that, but I've always done it that way. I use HHG only. I've had one failure, (out of 25 builds, and a bunch of bridge replacements and re finishes) which happened almost as soon as I strung it up. I believe I heated the bridge too hot before gluing and starved the joint. I used to just (blindly) heat the bridge on a hot plate. I now monitor the temperature, and heat it to 110 degrees.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

You guys are funny. A couple of screws takes care of this situation.

Bob Gleason from Pegasus Guitar and Ukulele has a tutorial on his web site.

http://www.pegasusguitars.com/lacquer_removal_from_bridge_foot.htm

Enjoy!

Philip

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aka konacat

If you think my playing is bad you should hear me sing!
Practice breeds confidence and confidence breeds competence. Unfortunately, I'm stuck in practice.

Interesting that Mr. Gleason is yet another advocate of leaving a border of lacquer (1/16") and relieving the edge of the bridge to clear it. Various ways to relieve the bridge edge, but all attempt to avoid removing finish right to the outer perimeter of the bridge.

"...but all attempt to avoid removing finish right to the outer perimeter of the bridge."

Right, because that way it's much easier to get a clean look at the edge of the bridge. A sharp chisel used as a scraper removes finish quickly and easily and a small rabbet on the outer bridge edge (you can quickly scrape with a new razor blade using your thumb as a depth guide) allows the bridge to sit nicely for good contact with the top.

I'd love to see your technique, Howard. Not quite sure what you mean by slicing. Are you cutting toward the score line, away from it, or parallel to it? Are you getting the chisel edge under the finish and lifting it, or paring the finish until you get down to wood?

Thanks -

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Paring, mostly cutting across the top, parallel to the long axis of the bridge, perpendicular to the grain of the top.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Thanks, Howard.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

This thread has got me thinking again about the idea of using epoxy (thickened) to glue bridges on. I imagine there will be some strong opinions against that here, but I see some advantages that seem to me to make it worth serious consideration. I think I'll start a new thread to think out loud about this and see what some of you think. Tomorrow. Gotta go to sleep now.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/