Official Luthiers Forum!

I can see where a precisely routed ledge will serve the purpose of avoiding interference and contact with the finish thickness. Like I mentioned I use a mask. I don't like the plan of laying down material then doing more work to remove that material so the surface is pristine. Plus the chance of damaging the now completed finish. I don't contaminate the area in the first place. Anyway for many years I have just sanded a very slight bevel on the edge of bridge gluing surface. Has worked for me for many years and is invisible. If I decide to use a miniature router bit I'll have it cut a bevel as well to prevent the sharp edge from showing.

Here's how I make the masks:
http://www.kennethmichaelguitars.com/bridgemask.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

Not to high-jack the OP's original thread but routing a ledge on a bridge bottom and clearling finish accurately enough so that one has a "pocket" of sorts for the bridge to be clamped into is most certainly not required AND more guitars have been built though all of time without this process than with.

On the other hand I always viewed my own guitar making as not just excreting yet another stinkin... guitar but doing the details, going the extra mile(s), and providing upgrades that were not available on your run of the mill, high-end f*ctory model. To each their own though.

We didn't invent the pocket/ledge thing and as far as I know the earliest adopter of this practice that I can recall (but I could be wrong) is Bill Collings and Collings guitars. For those in the know about Collings they are superb instruments in every respect and in my view a very good example of what a f*ctory instrument can be when the maker is a stickler for the details and obsessed with quality!

It's harder to do the ledge thing, at least the way that we do it because we take the ledge very nearly to the bridge perimeter which requires 1) the ability to see well.... and 2) a very steady hand, and 3) the chops and experience from having done this hundreds of times to get it right. It also requires the ability to understand the process and what this process seeks to improve on.

Millions of guitars have bridges that have been slapped on, clamped and glued with lots of finish not cleared under them.... and the bridge spanning the finish termination ledge making for a not-so-great bond in the area that it's spanning the finish ledge with some dependency of finish thickness in the bridge patch area too.

Bridges do lift though and one can almost expect it in the life of an acoustic guitar. For those who sell you know all too well that our clients are not always obsessed with caring for our creations with vigor.... and instead they let them dry out, leave them in hot cars, expose them to very high RH, etc. helping anything that is not perfect give way in time.

Most of all though this practice, routing a ledge and making a mating pocket in the finish does have notable advantages or Bill Collings would not be dong this on their guitars.

First far more gluing surface is available with only one method providing more gluing surface and that is clearing all of the finish under the bridge. Some very good repair guys do this and take it to the perimeter and exploit every bit of gluing surface. It works well but be a little off and it will show. Time, shrinkage, cold creep depending on one's choice of glue can all expose bare wood though which does not happen with the pocket method.

When using HHG to glue bridges or even Titebond the pocket provides a hedge against the bridge skating around on wet glue while clamping it in place which is a welcome thing.

Regarding the appearance the finish tucks under the bridge, no glue lines are visible, and it makes for a very neat and professional look.

Most importantly though and depending on what degree one takes this too nearly all wood-to-wood surface is exploited and put to work to help hold the bridge on and that's desirable, always.

It is necessary - hell no. Can a great guitar be built without this method - hell yes.

On the other hand it all boils down to what your bag is or more specifically what your value proposition is. If you are intent to do the very best work that you know how to do, always, and if you are keen to offer a level of value, attention to detail, and quality that exceeds others this is one of those things that will never be noticed, no one will ever thank you because the bridge stayed on and in place... At the end of the day though we prefer this method because we believe it to be superior to other methods, for now... things change... and we are very keen to do the best work possible at all times.

Going back to where I began... again it also depends on what your specific value proposition will be or is. If you are keen to do the details even the ones that will never, ever be noticed because.... well.... that's who you are this is a very good method and has notable benefits.

Required though? Not at all.

Agreed Hesh. I've had hundreds of guitars in my shop this year alone that had no bridge lifting issues (and several dozen that did) and I'm certain that many, even most, have a lacquer border under the bridge with no special allowance made for the loss of glue surface. Some will eventually fail, some won't. I've never been completely comfortable with these borders from the first time I learned to glue a bridge on. My own process has been worked out by trial and error with consideration given to the methods of others. On my new builds, I require a perfectly clean mating of the bridge and top with 100% assurance that the bridge isn't going to lift because of inferior glue contact. As we have seen, there is more than one way to accomplish that. Mine works for me beautifully and there was some pain involved in getting it worked out. I'm sticking with it, no pun intended!

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It will probably be alright.

It is not a very good picture of the cuts but they do wind up even. There was a learning curve. They are almost never even on the first pass, especially the corners, and multiple passes with varying degrees of pressure are usually necessary. I can see how the free hand method would work just as well once you got the hang of it.

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

Can you guys tell me what exactly you are using for the masking tape under the bridge?

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Formerly know as Mandodiddle.

To make masks I use 3M green from the auto paint store.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Joe White turned me onto to Fishers Film which can be found in art supply houses, great stuff. One of the advantages of Fishers is the thickness is predictable and consistent which is desirable of course.

Frisket film, Matte, low tack.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Fishers Film --- I think its made by 3M I am going to give it a try, I assume it stays put when applying the first coats which is a problem with some tapes when using nitro based coatings.

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Ken Cierp

http://www.kennethmichaelguitars.com/

That's it! Thanks Colin!

Ken I've used it with nitro and it stays down fine and better still does not leave any adhesive on the bridge patch but I would scrape anyway just prior to gluing.

I'm looking for a tape to place on top of a waterbase finish (EM6000) to outline the bridge that won't pull/damage the finish when removing. Any suggestions?

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Formerly know as Mandodiddle.

Frisket film low tack as above maybe, but it might be a bit delicate at 2 thou thick - depends on what you want to do with.
Do you want to protect the finish on the top while removing it from the bridge area for gluing?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I want to draw an outline of the bridge on the tape. Score a line just inside this drawn line on the tape. Remove the tape inside the scored line. Then route away the finish inside the scored line. (Using the tape left outside the scored line to rest the router base on.)

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Formerly know as Mandodiddle.

Bill two things: First I would test on scrap. I never used this film on top of finish, any kind of finish so I would test first.

Second what I did was trace the bridge on top of the film and then cut off the excess film but, and here is the difference, before the finish was sprayed. Then I sprayed over the tape and after the finish had cured carefully with a single edged razor removed the film and it always came up very clean with no issue. Doing it this way avoids any concern for the adhesive eating the finish regardless of what kind of finish it was/is.

To take the discussion in a very slightly different direction, can you mask the bridge location when you French polish? I'm guessing the rubbing would mess up the mask to the point where it wouldn't work at all.

Am I wrong?

As always, thanks in advance.

Steve

Yes and I really like this process

https://www.youtube.com/watch?v=lsGTJlLACYg

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Ken Cierp

http://www.kennethmichaelguitars.com/

It will accumulate shellac at the edge of the mask, but otherwise doesn't cause any trouble. Just make the mask a little undersize, and you can chisel or route away the ridge the same way that you'd clear the whole bridge area if you hasn't masked it.


I use a paper mask, with a few bits of blue masking tape that I've stuck on my arm a couple times to de-sticky.

I have always used low tack drafting tape in liberal amounts. No issues on many guitars with water based, nitro, and cat urethane finishes. Never tried with shellac/French polish.

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

My daughter, a repair tech in Brooklyn, learned of a cool tool from one of her "old guy" mentors. It is called a mezzotint rocker and is used to roughen up the surface of an engraving plate so it holds more ink. He uses it to "pulverize" the lacquer under a bridge for easy removal. This is what it looks like - this one is 1/2" wide:

https://www.flickr.com/photos/ruby1638/18531834688/in/album-72157654016889888/

Here is a page from his site - look halfway down:

http://www.lutherie.net/B-25_bridge2.html

Here is the company site and page:

http://www.eclyons.com/index.php?main_page=index&cPath=12

Note that it looks just like toothed plane blade, and if you have one you could cut it down, or order one like this and put a handle on it. Highland has them in all sizes from 1/2" wide on up:

http://www.highlandwoodworking.com/palmplaneblade275mmtoothed.aspx

My daughter's - in the first pictures - is 45 teeth per inch and she loves it but says she would get fewer teeth per inch if she had it to do again.

Ed

Bump

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Max Bishop
Brighton, Michigan

Great idea, a worthwhile tool to have around. Lee Valley also has toothed blades available for their detail palm planes that are good (I have the toothed blades and the palm planes). 1/2" Wide so about the same size as the Ibex.

http://www.leevalley.com/US/gifts/page.aspx?p=67716&cat=1,41182

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Steve Smith
"Music is what feelings sound like"

Research done by the US showed that a toothed glue joint was not as strong as a smooth one. It may be good enough for a guitar bridge but why spend the money on one?

Wednesday I agree and that's been posted here before but I think in this case Ed's daughter who is a friend of ours too by the way is advocating the use of the tool not to tooth a glue joint but to get old lacquer to lose adhesion and flake off. I could be wrong but that's my read of the post above.

It's a cool idea for that!

Hesh, that was the way I read it as well.

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Steve Smith
"Music is what feelings sound like"

I understood that the purpose was not to surface the wood but in removing the finish texturing would be inevitable I would think.