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On my last few guitars I have put a micro bevel under the bridge to ensure good fit. I have found this exercise challenging and I wonder if it is really necessary. On previous builds without it, the bridges have not come off and they sound fine. (I guess those folks that scribe the finish around the bridge don't have this issue...) I like to make sure I have enough finish under the edges of the bridge. So, what's your thoughts? ...bevel or not?

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Well, what were you thinking of doing?
You really need good contact for gluing.
I used to just scribe the finish and chisel it off, but could sometimes see small imperfections.
Last build I tried routing a ledge/rebate around the bottom of the bridge, undersized Friskit to mask the footprint then removing the last of the finish to about 50 thou short of the bridge outline.
While nervous of the whole process, I was well pleased with the results, and it wasn't nearly as difficult as I thought it would be. Trickiest part was getting the depth setting (finish thickness) for routing the rebate.
It was just a process of trial an error to match to the finish thickness using thin maple strips, until the ledge would just slip over the "step"
I'm a convert.

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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 do not have a micro bevel set up ---- however I have always sanded a tiny slope all along the bridge perimeter to provide clearance (since 1966) I believe it provides adequate coating over lap relief and is still invisible to the eye.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I make a small rabbet/rebate with a scraper. Same difference.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

I use a razor blade as a scraper to make the bevel. The blade is clamped in 1/2" dowel that was split length wise and has a nut/bolt to clamp it together. I let the razor hang out about 0.050" or so. I made the scraper for bindings but it works well for this as long as the bridge material is not too soft.

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Steve Smith
"Music is what feelings sound like"

It's optional but we do it and believe in it too. So does Collings and since the last time that this came up on the OLF David Farmer educated me that Taylor does it too.

It's important to understand what the benefits are before deciding if it's for you or not. Here's what I like about the idea of the rabbet on the bridge bottom:

1) If you have ever removed a f*ctory guitar bridge you may have noticed that f*ctories can leave a LOT of finish under the bridge eliminating wood-to-wood contact. It's often one contributor to why some bridges lift especially when the wood-to-wood contact is not good on the back edge of the bridge where the heavy lifting is done in keeping it in place.

Using a rabbet can and does in our repair world greatly expand wood-to-wood contact and I've even measured one example where the maker, a f*ctory, left 40% of the available gluing surface under thick finish.

With this said the major functional benefit of using this technique is more gluing surface on a critical, under constant tension component while preserving perfect cosmetics around the bridge.

2) No one likes the look of a bridge where the finish has been cleared to the perimeter of the bridge where with time, RH swings and if the wrong glue was used and there is creep the cleared finish area becomes visible for all to see.

Additionally repair folks may hate a guitar where the finish was cleared to the perimeter because it will often require some level of finish touch up if the bridge has to be removed, or lifts..., and reglued. We like our repairs to be as good or better than new.... and this means invisible.

Although clearing finish to the perimeter is as much wood-to-wood area as possible a .050 rabbet is really mouse nuts in terms of losing gluing area.

With this said we prefer the rabbet over clearing to the perimeter.

3) When you rabbet the bridge you also clear the finish to match and create a "pocket" of sorts where the bridge will "snap" into the well that we created. What's great about this is when using HHG, you all use HHG don't ya........, and time is limited being able to slide the bridge into a resounding detent and then sung up the clamps just makes one's day! It's also beneficial in not gluing the bridge on in the wrong location and also stops the bridge from sliding around during the application of clamping pressure.

The bridge rabbet is part of a system and in my view needs to be thought of this way. Although you can do it with Titebond with no issues it really shines with short open times such as HHG.

For you guys your finish thickness should be predictable. You know how much finish you shoot, presumably or often have experience with prior instruments and you should be able to closely predict finish thickness. When you can't, such as in my repair world, measuring finish thickness is easy and that's what the depth is set to, what we measure.

One last thing if I may please.... When I was building my goal was never to approach the quality of the best f*ctory instruments. That bar is pretty low in my experience.... Instead as a custom builder I always believed that our value add was to take it to new levels, do all the tricks, hot rod the thing so that the value proposition is "superior" to that of a f*ctory instrument. Being sure to build in "serviceability" for extended life AND doing all that we can to add value to our instruments was in my view what this is all about.

Rabbeting bridges is one small and easy thing that we all can do to help ensure that folks like me won't be billing our mutual clients when the guitar that they bought from you has a bridge failure.... It still can happen mind you but if you take advantage of all but say .050" of bridge perimeter as available gluing surface your bridges will likely require more trauma to make them fail.

Can a great guitar be built without rabbeting the bridge - sure and they have been for over 100 years now.

With this approach, how far does the finish extend under the edge of the bridge?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Could you expand on this, Hesh?

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

No way man.....

Brave man Alex

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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 can certainly see all the benefits of doing this, but isn't a bevel all around the edge of the bridge creating a stress riser in the worst possible place?

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I don't think it would prodouce any more (or less) of a stress riser than a bridge glued with 90 degree sides (all things equal like finish obstruction. . .). I could be very wrong though, I've never been to the front end of a train, much less driven one.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

....fearlessly the idiot faced the crowd, smiling.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Run a razor around edge. No power tools needed. I understand the concept, but the amount of material removal is very small. You can achieve same result with idea above. Very light amount of scraping. And, I use the LMI bridge clamp. Pulls wood in both directions.

I'm sure you're probably right and I'm over thinking it, but I was always taught that as the angle between the 2 surfaces increases between 90° and 180° the force theoretically goes to infinity. For example, a scarf joint that hasn't had the end glued down properly is liable to get cracks starting at that point. Seems like it'd be the same in this situation.

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I would say that the rabbet or bevel simply reduces the area/footprint of the bridge, the glued surfaces are still 180 to 180 --- at least that is how I see it.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Has anyone come up with a good template method to control where your router is going when routing out the finish for the bridge footprint? I would be a little nervous doing it free hand.

I use one of the die grinder inlay tools from Blue's Creek with a 1/8" downcut bit and I eyeball it. Not too hard if you have a steady hand and an Optivisor.

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Steve Smith
"Music is what feelings sound like"

I haven't, I tried a method based mixing what Hesh and some others suggest (IIRC), pulling back the bridge itself about 50 thou and scoring round it with the back of the point of a sharp scaplel blade.
As I mask an undersized bridge footprint before spraying, after that's removed I'm left with an narrow band of finish that's easily removed with a small sharp chisel.
I just feel it's a process more easily controlled than a router and there's no danger of the finish chipping out at the edges.
Quick light wipe with abrasive and it's ready to go.

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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.

That sounds safer than the method I now use where I freehand a chisel up to the edge of the bridge where there is no room for error.

Can we stop calling a rabbet (or rebate for you folks across the pond) a bevel. A bevel is an angled cut as in a beveled mirror. What David and Hesh are doing is cutting a stepped cut more properly called a rabbet. A binding "channel" (should be called a binding rabbet) is an example of this kind of cut. Champer is a bevel that most of the time refers to somethng at 45° and a bevel is an angled surface connecting two adjacent surfaces more or less.
L.

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Cut to size.....Beat to fit.....Paint to match.

Thanks for the definition clarification ---- but in this thread we are talking about both those machining operations. I for one actually do shave or sand a bevel/chamfer (which I could do with a router bit) as opposed to using a router and fixture/jig/attachment to make a step or rabbet on the perimeter.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Some are routing a rabbet and some are scraping a bevel.........worlds apart I believe the rabbeted bridge and the recessed pocket to bare wood is the way to go.

I used to just bevel the edge but now cut a rabbet with the razor blade clamped in a split dowel thing I spoke of earlier. I also think the rabbet is the way to go.

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Steve Smith
"Music is what feelings sound like"

Do you have a photo of your tool? I'm having a hard time picturing exactly how it works.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter