sanding the bottom of a bridge

[mandrew]

I have Robs ebook, which is great, but one thing is not clear. He asks you to look at the bottom of the bridge where it meets the instrument, to see if you can see light. Then he instructs to see if paper will slide under it, and says that if it does, it definitely needs attention. I can see a lot of light, and have removed the bridge/saddle to sand the foot area down. He says do this until it fits pretty well. What is "pretty well?" Should there be a little light, or no light, so that there is constant contact across the entire bridge? I don't want to take too much.

[Denny Gies]

I think "no light" is the desired result. I did a replacement bridge on an old Gibson A by setting the sandpaper updidedown (rough side up) on the top, where the bridge goes, and then rubbing the bridge feet over the sandpaper until there was no light showing. Good luck.

[John Flynn]

A luthier friend showed me the trick of taking a .002" feeler gauge and running the corner of it around the base of the bridge foot where it meets the top of the mandolin, trying to "wedge" the gauge in between the two. Ideally, you should be able to go all the way around and not be able to get the feeler gauge in anywhere. It's a tall order!

The linked page has great advice on fitting bridges:
http://www.frets.com/FretsPages/Luthier/Technique/Mandolin/FitBridgeFeet/fitfeet.html

[Marc Berman]

Just to be clear - he's talking about the two feet. Most adjustable mandolin bridges have an arch in the middle so there is no contact there.

[violinvic]

I use the sandpaper method described above, moving the bridge laterally appx. 3/4" in a light sanding stroke. When you think you are close, mark the contact points with a pencil and sand lightly until the pencil marks are gone. Keep the bridge perpendicular to the top. I use 220 or 320 paper. Pals, Vic.

[Nevin]

You can also use chalk or lipstick. Apply it to the mandolin where the bridge rests. Place the bridge in position. Take it away. The chalk or lipstick will be transferred where they meet. Ideally you get the chalk on the entire foot. Sand, scrape or use a violin makers bridge knife until you are happy.

[jim simpson]

Has anyone here ever tried a contour guage?

[Gerard Dick]

Stewmac has a jig with a roller foot that you bolt the bridge onto and then roll it back and forth on the sandpaper. It keeps a constant angle. Look it over. It's not too hard to cobble a reasonable facsimile together that will do the same thing. I made one in an afternoon. :mandosmiley:

[Richard58]

Violin bridge fitter jig

[Ivan Kelsall]

Sand the bridge feet from side to side instead of towards the neck & away from it.That way you won't get the front & back edges of the feet rounded & you don't need any jig to do it. Those jigs are usually for luthiers,not for a 'one off' bridge fitment. Remove the bridge saddle as well,that helps in keeping the bridge feet rock steady. Aim for 'no light' under the feet & take it slowly,checking as you go. I'd only had my first good mandolin for a month or so when i fitted a Cumberland Acoustic bridge to it. I'd never done it before,but i took my time,sanded side to side & did a first class job,as anybody can do,
Ivan

[John Flynn]

Just to be clear - he's talking about the two feet. Most adjustable mandolin bridges have an arch in the middle so there is no contact there.
Thanks Marc, I should have been more clear. With a bridge that has two feet, you would run the feeler gauge around the outside of each foot where the feet are supposed to be contacting the top.

[Stephen Perry]

Sanding will pretty much inevitably leave a less than ideal fit. At least for me. I end up using a scraper and chalk fitting. It's been discussed on here a good deal. 2 thou is a lot of space.

[Mike Snyder]

May be obvious, but I'll say it. You will NEVER get the best sound posible from your instrument until the bridge fit is perfect. Or as near as a PROFESSIONAL can get it. You guys are better woodworkers than me, I'm sure. There are things my luthier does. Frets and bridges are two of them. I make my own banjo bridges and I can tune them up pretty good, but the bottom is FLAT!!!!!
The arch of your mandolin may be nice and parabolic. Smooth, even, easily matched in ebony. Mine is an uneven and, frankly, lumpy-looking arch. Me wiggling about with sandpaper would not get it. And using your eyes, wow. If you're seeing light, you've got major gaposis. A good luthier won't consider that a STARTING point.


PS - Mine may not be beautifully arched, in fact it's not, but the sound is there. In spades. Come to Winfield in September and play it.

[John Flynn]

I have an A4 by a major small builder. (see my current avatar). The top got wavy on the treble side. A luthier had to re-humidify for a week with the tension off and then install an additional brace. That put the bridge fit out of whack, so it still didn't sound right. It's a hand-built single foot bridge with a very thin foot. I had another luthier who has a great rep for mandolin work do some surgery on the bridge and he said the fit is as good as he can get it. There is no light showing through, but I can still get the feeler gauge under it in some spots.

However, the instrument sounds really great now, better than when it was new. I am completely satisfied with it. I tell the story because while I agree that a perfect fit is ideal, it seems it's possible to get great sound with just an OK fit.

The other point I wanted to make, and most people here will know this, is that no matter how good your fit, it's advisable to check it after every string change. It's common for the bridge to get pulled slightly away from the tailpiece during a string change resulting in a gap in the front. Then you have to coax the bridge back into position.

[kkmm]

I have done this once and would not consider (and would not recommend) it the proper way do get the bridge to fit.
I called it the "lazy man" process.
1) lay a small sheet of clear plastic (plastic wrap for example) on the top where the bridge would be
2) spread a layer of epoxy on it, again where the bridge would sit on
3) now put the bridge on it (at the correct spot for good intonation) and tune up the strings
4) the bridge bottom will be submerged in epoxy, make sure to wipe off epoxy from both sides of the bridge
5) next 24 hours, once the epoxy has been set and cured, loosen the strings to remove the piece of plastic
(it's kind of hard, but it could be done)
This worked great for me, there is no gap between the bridge and the top, I could not slide the thinnest feeler gauge under the bridge at all. I had no idea whether it sounds better or worst than before, but it does sound loud for this mando.

[John Kelly]

Lots of excellent advice here on what to do. I'd like to highlight the point Ivan makes about not moving the bridge back and forth towards and away from the tailpiece as it is very easy to sand a curve into the foot as you move the bridge and end up with poor contact - this is what the jig is designed to eliminate.

Another point is to check when you have restrung and brought the instrument to pitch, as there can be a slight variation in the profile of the top when string tension is applied and this can introduce slight gaps once more.

[Mike Conner]

As John and others state, some good advice here.

Following the Frank Ford Frets.com method has worked well for me, and I feel that using a pocket knife to scrape a slight hollow into the center of the bridge feet reduces the tendency to create a curved bottom, and it also greatly reduces the amount of material to sand off. Typically, when the hollow is very nearly gone you are done!

Good point on deflection of the top (or maybe even the bridge feet) under string tension. On some instruments, I have found that I need to compensate the fit a bit to eliminate a gap at the tips of the feet when at string tension.

//mike

[John Flynn]

I have done this once and would not consider (and would not recommend) it the proper way do get the bridge to fit.
I called it the "lazy man" process.
1) lay a small sheet of clear plastic (plastic wrap for example) on the top where the bridge would be
2) spread a layer of epoxy on it, again where the bridge would sit on
3) now put the bridge on it (at the correct spot for good intonation) and tune up the strings
4) the bridge bottom will be submerged in epoxy, make sure to wipe off epoxy from both sides of the bridge
5) next 24 hours, once the epoxy has been set and cured, loosen the strings to remove the piece of plastic
(it's kind of hard, but it could be done)
This worked great for me, there is no gap between the bridge and the top, I could not slide the thinnest feeler gauge under the bridge at all. I had no idea whether it sounds better or worst than before, but it does sound loud for this mando.
Wow. That's interesting. I like that kind of thinking, but I wonder if epoxy has the same tone transmitting qualities as wood. Perhaps something like DAP Plastic Wood could do the same thing. It also seems to me that a person could put a very light coating of something like Tri-flow on the plastic, so it wouldn't stick.

LOL. The luthiers on the Cafe' are probably having fits reading this! :disbelief:

[dang]

The linked page has great advice on fitting bridges:
http://www.frets.com/FretsPages/Luthier/Technique/Mandolin/FitBridgeFeet/fitfeet.html

This method worked for me also the few times I have had to do it.

[Ivan Kelsall]

This clip was posted onhere a short while back. It shows Wayne Henderson finishing off one of his F5 style mandolins.He uses the side to side method of sanding the bridge base,as does another great luthier,Gale Hester,
Ivan;)

http://youtu.be/2NQ8xRBaQOs

[seg]

This clip was posted onhere a short while back. It shows Wayne Henderson finishing off one of his F5 style mandolins.He uses the side to side method of sanding the bridge base,as does another great luthier,Gale Hester,
Ivan;)

http://youtu.be/2NQ8xRBaQOs

Thank you so much for this info! I'd been scraping my bridge for several hours and it didn't look much better than before I started. I then used this side to side sanding method and quickly had a perfect fit!!! Thank you (and Go Sox)

[sunburst]

I use a method I haven't seen mentioned in this thread.
If the mandolin is new, I fit the bridge before buffing the finish, but if the mandolin is not new, the top finish must be protected, so I put some masking tape (the thinnest I have) over the bridge position on the top, then place the bridge in position and hold it there with a strip of 320 grit sandpaper under one foot. I pull the sandpaper strip so that it slips between the bridge foot and the top a little ways. Now, look at the bridge feet for the scratches (streaks) left by the sandpaper. Scrape them away and repeat. Alternate bridge feet from time to time. Eventually, the sandpaper will rub the entire surface of the bridge foot, and since the bridge wasn't moved from it's proper position during the fitting, and since the actual cutting of material from the bridge was done with a scraper (the sandpaper is to mark the places to scrape, mostly) the fit will be very good. Remove the tape from the top of the mandolin, check the fit of the bridge, and if any adjustment is needed, I use a little chalk and tidy up the fit.

[fscotte]

Has anyone here ever tried a contour guage?

Yup. Transfer the contour to the bridge with a white marking pencil, rough sand it to the line with power sander, then I do the typical sanding method by placing sandpaper on the mandolin and move bridge sideways. Takes about 5 minutes I'm done.

[Paul Hostetter]

Sand the bridge feet from side to side instead of towards the neck & away from it.

Couldn't disagree more. Side to side, the arch changes. You've fitted your bridge to nothing of value.


Has anyone here ever tried a contour guage?

Not terribly useful, and in fact, many people try to use this and leave a permanent track of indentations across the top of the instrument. Only worth doing if you really know how, and take the right precautions to protect the top. Laregly unnecessary if you know what you're doing.

Btw, it's gauge, not guage. :disbelief:


A luthier friend showed me the trick of taking a .002" feeler gauge and running the corner of it around the base of the bridge foot where it meets the top of the mandolin, trying to "wedge" the gauge in between the two. Ideally, you should be able to go all the way around and not be able to get the feeler gauge in anywhere. It's a tall order!

For a beginner, but if you work at it, and get it right 50 times, you achieve the vacuum fit required for good sound transmission.

No one yet has mentioned how to compensate for the inevitable sagging of the top under tension. If you fit it to the top with your little piece of sandpaper, and think you've got that right, nine times out of ten, it won't fit after you tune it up.

[Ivan Kelsall]

Quote - "Side to side, the arch changes.". On both my mandolins,closer to the neck away from where the bridge sits,the top slopes down towards the neck & flattens out quite a bit.Side to side,where the bridge sits is more of a constant radius,
Ivan

[Stephen Perry]

Paul, I'd be curious as to your method of taking distortion under pressure into account.

[Lou Giordano]

Paul, I'd be curious as to your method of taking distortion under pressure into account.

Me too.

I have to do a better job on mine. I did not get it as good as I wanted.

[Paul Hostetter]

On both my mandolins, closer to the neck away from where the bridge sits,the top slopes down towards the neck & flattens out quite a bit. Side to side,where the bridge sits is more of a constant radius

On the hundreds of mandolin bridges and thousands of violins/violas/cellos/basses bridges I have fit over the last fifty years or so, that's not how it has worked out for me. Not that I haven't tried the lateral thing—I have, or at least did a long time ago. It just wasn't as effective.

To Stephen and Lou: after getting the feet trimmed as close as possible by hand with the top at rest, I tape the sandpaper (usually 150) to the top and carefully work the bridge under pressure over the paper over the area of eventual contact. This requires keeping the angle of the bridge correct front to back, so it doesn't end up pre-tipped the wrong way, and also requires some educated pressure. Violins and violas I do in my lap. Mandolins, cellos and on up I do on the bench. But getting the right amount of pressure to anticipate the future fit involves a learning curve, as different instruments' tops exhibit a different amount of flex.

Here's one that, while it's a continuous one-footed item, still illustrates my point:

http://www.lutherie.net/gibson.bush.mandolin.bridge.jpg

That bridge probably fit right when the top was at rest, the way they do when you use these things:

http://www.stewmac.com/product_images/1lg/5046/Archtop_Bridge_Fitting_Jig_Detail.jpg

...but look at how the ends have lifted under tension. Useless mass out in space.

Many of us have seen the impression left by bridges after they've been on for some time. Quite often the divots are all in the middle, but over time everything slumped so the ends of the bridge finally touched. That's possibly what will happen with the Sam Bush F-5 above. Or not. In any case, it's not the best way to do things.

I think it's worth the effort to get the bridge really well fitted from the beginning, because it will tend to stay that way for ages. I just checked a bunch of old Gibsons around the house and in my shop, and they managed to get it right most of the time. I think most of the problematic ones are after-market bridges, ones that were put on later by people who just bought a bridge and thought it would fit. They almost never do, and they don't have enough natural flex to adapt to a curved surface.

[Ivan Kelsall]

Honestly Paul, if i saw a gap as per your pic.under the bridge feet on either of my mandolins,i'd whip it off & re-sand it. Using the Stew-Mac sanding fixture begs one question :- If the area where the roller is running is 'one contour' & the bridge area is yet 'another contour' (as both my mandolins are),how accurate is the finished bridge foot contour ?.Taking it to an extreme level - if the area where the roller is was totally flat & running 'up-hill' towards the bridge area,the bridge would be lifted off the top of the mandolin completely. On both my instruments,there's quite a difference in the contour closer to the neck than the contour at the bridge position & i don't think that using a sanding fixture would help at all in obtaining an accurate contour for the bridge feet. The roller needs to run on the same contour in order to be accurate. You can't have the roller running on one contour while the fixture is trying to sand to another. Whether you agree or not,i used the side to side method of sanding a CA bridge to fit to a mandolin. It took me 4 hours & a lot of constant checking,but it was as accurate as it could possibly be - i couldn't accept it any other way,
Ivan~:>

[Stephen Perry]

I have the saddle off and do fitting at the end with the posts squeezed in a bit - accomplishes the the same thing! Then a polish under pressure with 600. For deformed tops, make some estimates and see how I can slide it in. Squeeze and put in place with dilute lipstick on the top to see where I'm contacting.

Thanks!

[Paul Hostetter]

You're quite welcome. There's more than one way to skin nearly any cat. :cool:

Ivan - much of what you point to is why I don't have any use for those things. They get things fitted only approximately, at best. I can do what they do by hand and eye, then finish it by touching off the bottom with the sandpaper. I also have misgivings about those gizmos because people often leave tracks in the finish.

[Lou Giordano]

The first time I tried to fit a bridge I used coarse sand paper. The grit of the sand paper made impressions in the finish. Brilliant!:disbelief: They buffed out but, I had a fit when I noticed them. I guess the paper was too thin.

I often have more guts than brains when it comes to tinkering.

[Folkmusician.com]

Fitting bridges is not as straightforward as it seems. It takes a good deal of practice to be able to fit one to a top that is not uniform. I just fit this bridge to an MD305. As pictured it is getting perfect contact with the top under full tension.

118367

[Dan Krhla]

The stew Mac jig page has a video of someone using it. Clearest explanation I've seen. Its arch top guitar but gets the point across well


http://youtu.be/-c9r6Nl0Yas

[Pete Jenner]

I've always done side to side with pretty good results but I can see that the 'Sunburst' method makes sense. I''ll try that next time.

[Dr H]

A couple of questions occured to me while reading this thread, that maybe someone here could address? I don't want to derail the discussion, so if there's another thread more pertinent to my questions already going, a pointer would be appreciated.

First off, as Marc points out in post #4, a lot of adjustable mandolin bridges have two feet with an arch between them. The feet contact the mando top, but the arch usually clears it by a 16th inch or more. However, in tthe video Dan provided in post #34, the bridge is fitted to the guitar top in one continuous arch -- no feet; no space.

This is all consistent with my experience: three of my mandolins have an arch between the feet that is not in contact with the top; my archtop guitar has one continuous "foot" that contacts the top along it's entire length.

* My question is, what are the feelings here regarding having two separate feet, as opposed to one continuous contact surface for the bridge bottom?

Intuitively, it seems to me that more contact would be better, but intuition isn't always the best guide. Would there, for example, be any reason to try the continuous-style bridge on a mandolin, or is there some reason why that shouldn't be done?



* My second question is, what are the feelings about using adjustable bridges, as opposed to a single piece fitted bridge?

The advantages of an adjustable bridge are obvious, but I have to say that on the instruments that I've owned for years I've never touched those adjustments once I decided on the string gauges and heights I wanted, and the instruments settled in. So wouldn't it be just as good -- perhaps better -- to just have a solid, one-piece bridge made to appropriate specs? Always seemed to me that the fewer moving parts you can get away with, the better off you are. :)

TIA.

[sunburst]

Sometimes the top of a mandolin has enough structural weakness that the bridge feet start to distort the top. In those cases, a continuous base (as opposed to a 2-foot base) can help preserve the shape of the top arch.
When the top is in good shape, there doesn't seem to be much difference in structure, performance, and sound between adjustable bridges with continuous bases and those with feet.
I like to cut the arch between the feet so that the base starts to feel somewhat flexible. As mentioned in this thread, string pressure can distort the top arch slightly and the bridge base must be fit so that there is good contact with the top when under string tension. It hasn't been mentioned that the top arch changes shape (as all wooden objects do) in response to moisture content of the wood. That shows up as changes in the mandolin in response to relative humidity. If the base has a little flex, it can fit the top better when the top changes shape, whereas the fit of a continuous bridge base can change with the changing of the top arch shape. I think of the center arch of the base providing somewhat of a hinge to help keep the bridge feet fitting the top under many circumstances.
The mass and internal damping characteristics of the bridge have more to do with sound than whether or not the bridge is adjustable, but obviously there can be significant changes in mass and damping between adjustable and non adjustable bridges, so we can sometimes hear a difference. Whether one or the other type is an advantage then, comes down to which sound we prefer.

[Paul Hostetter]

Well put, John. Quite a number of bridges I've fitted started out with the cutout between two feet, but by the time it was really mated to the top, it was one continuous foot, like the bridge on the F-5 in my post #28.

I haven't found a huge sound difference between a one-piece bridge like this:

http://www.lutherie.net/gibson.non-adjustable.bridge2.jpg

...and the standard later adjustable. They're different, but not as much as one would expect. Some folks don't hear any difference.

BTW, someone mentioned how a bridge can leave an impression in the finish on a top. Here's an A-00 where the bridge had rocker (not sandpaper) tracks in the bottom:

http://www.lutherie.net/A-00.bridge.impression.gibson.jpg

The marks were clearly made when the finish was fresh.

[Jim Adwell]

* My question is, what are the feelings here regarding having two separate feet, as opposed to one continuous contact surface for the bridge bottom?

Intuitively, it seems to me that more contact would be better, but intuition isn't always the best guide. Would there, for example, be any reason to try the continuous-style bridge on a mandolin, or is there some reason why that shouldn't be done?

A continuous foot would have more area in contact with the top, and so would have less pressure per square [your length unit of choice] that a two footed bridge of the same width and length. Whether this matters or not, I have no idea, except that I modified a continuous foot bridge on a mandola I built to a two footed bridge, because the continuous footed bridge looked odd to me. The tone may or may not have been slightly better after the conversion, but not much change at all, if any. I sanded an arch into the bottom of the continuous foot bridge to make it two footed, so the same non-adjustable bridge with less contact area and mass after the conversion.

[Dr H]

Thanks for the replies. What I seem to be hearing is that it's a 'six of one; half dozen of the other" kind of situation.

Sunburst's point about the arch providing something of a flexible "hinge" which will accomodate minor changes in the arch of the top due to humidity and such, makes a certain amount of sense to me. On the other hand, everyone seems to agree that good contact between the bridge and the top is essential for good sound, and wouldn't contact be "better" with a continuous-foot bridge than in one with an open arch? (Assuming both to be properly fitted, of course...)

As to the adjustable versus fixed bridge, my thought was that with a fixed bridge, you once again have better contact, since you have a continuous mass between the strings and the top.
With an adjustable bridge you really only have two points of contact -- where the saddle rests on the adjustment nuts. It seems like this would favor transmission of vibration from the 1st and 4th courses, and be less efficient for the two inner courses. But I don't know that for a fact, as I've never actually compared two otherwise identical instruments fitted with the different bridge styles.

I guess on the one hand, with a fixed bridge you're not going to accidentally knock it out of heighth adjustment; but with the adjustable brigde you can make seasonal adjustments if needed. Though, as I say, once I got my bridges adjusted properly, I've not touched those adjustments again -- going on 20 years for one instrument. (I live in an area where the relative humidity is relatively constant through most of the year -- high, but constant.)

[Rob Roy]

I haven't done a lot of them but here's what works for me. On the top of the instrument I use couple of pieces of blue masking tap at each end of the bridge, leaving a quarter inch of space and mark the center line of the existing bridge before taking it off. With the new bridge in position, I use a thin piece of plastic binding (0.040) as a spacer to scribe a fine pencil line on the side of the bridge matching the top contour. Then I go to the oscillating spindle sander and true to the line. The tool maintains the 90 degree angle. It also makes quick work of the excess ebony. I've honed the technique to where I can split the pencil line, leaving very little sanding on top of the instrument.

I use 220 grit sticky back sandpaper between the blue tape, never a rougher grit as the friction makes it hard to keep the bridge level. I've found by accident that rather than try to move the whole bridge back and forth or side-to-side, it works better to pin one end down with finger pressure and work the other end forward and back in small angled strokes. This fanning motion is not ideal but pinning one end down eliminates the rocking motion I can't seem to avoid. I scribble pencil marks on the bottom side of the bridge before I start, when they're all gone and I see consistent, smooth 220 grit scratches, I know I'm there. On gloss tops I repeat with 320. Sunburst's method of keeping the bridge in place and pulling strips of fine grit paper through is the only method of truly mating the bridge to its exact position on the top. Allowing for top distortion under full load, now that's a fine art that must just come with doing a ton of them.

[fscotte]

I wonder if there's truly any noticeable difference between a bridge that is perfectly fit to the top, versus one that may be a little less than perfect. Is it just the placebo effect when one puts on a perfect fitting bridge or is there really something noticeable in a good way?

After all, you have two metal posts in the mix... Why would a little light at one end of the bridge feet make much difference?

[Richard58]

Iv fitted many violin bridges in the past. I also do small changes to the bridge that can affect tone such as thinning the feet from the thickness they come in. How much of the feet on the mando bridge is removed? Or is any removed off the top of the feet area. Are the sharp edges rounded off?

[MysTiK PiKn]

Sounds like every instrument is unique. There's no definite recipe. Lots of great info.

I'm surprised no one mentioned the experiments of Red Henry.
http://www.murphymethod.com/index.cfm?event=pages.content&contentId=87

My thought is to keep your existing bridge, which might not be so bad - and make a new one-piece, w 2 feet, from maple, ebony, rosewood, etc. and make it lighter by rounding edges, drilling holes, and cutting wings a la violin style, only thicker. And fit that.
I think I could do that in about a year. (that's basically Red Henry's discovery). Might be faster to buy one.

I like the idea of scribing to fit, and arching w perhaps a drum sander. (oscillating was mentioned, I don't know what that is). And then testing under pressure. It's no easy job, huh.

Great discussion. Thanks to all.

[JeffD]

The more I read, the more in awe I am of folks that know how to do this stuff.

[foldedpath]

The more I read, the more in awe I am of folks that know how to do this stuff.

Yeah, same here. I can do my own basic setup work, but I leave the subtle things like fret work and bridge fitting to the experts.

Last year I brought my Lebeda mandolin to Cat Fox in Seattle for fret work. I was afraid it was going to need a full refret, but she said a fret dressing was all it needed. She also said she didn't like the way the bridge was mated to the top, and offered to fix it. She explained how just rubbing the bridge against sandpaper wouldn't work (the 2-dimensional problem against a 3-dimensional surface), and said she fitted bridges by hand scraping with a knife. As it turned out, the bridge fitting was as expensive as the fret dressing, but it sure does fit tight now.

As a final note, I'm not sure how critical this is. The mandolin played like butter after leaving her shop, but I think that was mainly just her overall setup work with neck adjustment, bridge height adjustment, and truss rod adjustment after dressing the frets. Playability was improved, but the tone was in the same general ballparkpark after the bridge fitting.

I mean, yes... if you have huge gaps it's a problem, and I think this was money well spent. If nothing else, it kept the bridge mated to the top as the top starts to age and settle a tiny bit over the years. But if a two-foot bridge is 90% in contact with the top, I'm not sure that final 10% makes or breaks the tone. There is a lot more going on with mandolin tone than just how tight the bridge is in contact with the top.

[Richard58]

Sounds like every instrument is unique. There's no definite recipe. Lots of great info.

I'm surprised no one mentioned the experiments of Red Henry.
http://www.murphymethod.com/index.cfm?event=pages.content&contentId=87

My thought is to keep your existing bridge, which might not be so bad - and make a new one-piece, w 2 feet, from maple, ebony, rosewood, etc. and make it lighter by rounding edges, drilling holes, and cutting wings a la violin style, only thicker. And fit that.
I think I could do that in about a year. (that's basically Red Henry's discovery). Might be faster to buy one.

I like the idea of scribing to fit, and arching w perhaps a drum sander. (oscillating was mentioned, I don't know what that is). And then testing under pressure. It's no easy job, huh.

Great discussion. Thanks to all.

Sounds as if hard rock quarter sawn maple wood is better then ebony...for a bridge.

[Fred Young]

Maybe now would be a good time for me to try posting a picture in a reply. This is my take on Bridge setting tools.131906

[sunburst]

..
131918

[fox]

I have tried various methods on archtop guitars, with time and patience you can get a good fit using basic tools but, the easy fix for me has been.... to get a close fit then place a strip of tape over the correct position, sprinkle the tape with fine wood dust (ebony or whatever the bridge is made from). Then coat the bottom of the bridge with superglue & quickly press it down hard in place.

This has worked extremely well for me, I use electricians tape but cling film would probably give an even more accurate fit its just that I am a bit nervous the film might split a stick the bridge in place!

[Larry Simonson]

I think my thoughts parallel Fscotte when he posted earlier "I wonder if there's truly any noticeable difference between a bridge that is perfectly fit to the top, versus one that may be a little less than perfect. Is it just the placebo effect when one puts on a perfect fitting bridge or is there really something noticeable in a good way?"

It seems while we can't agree on sound/tone issues there is quite a bit of agreement on workmanship attributes and one of the easiest to spot is an ill fitted bridge and it seems nearly everyone thinks it is important to the sound/tone. Has anyone ever actually tested this theory and published their results?

[MysTiK PiKn]

Well, I'm not about to publish; but I made a one piece bridge, and sanding, fitted it to an Fhole Astyle cheap old plywood topped harmony mando - and it got lots louder, and I spose the tone was better. Problem was the bridge feet splayed just a bit; but worse, the plywood top sagged - both making the fit impossible. Even with all that, and the resulting lousy fit, it sounded a lot better. So bad fit is certainly cosmetic; but good transmission of sound can be achieved better with better fit, better wood, and no adjusto metal. One could also vary the thickness, weight, and material, etc etc etc. And to publish all variables? Well, Red Henry tried, and published a lot of results.

I have no affiliation with Red Henry. It's just useful info to me, and maybe to others. But he sells bridges, and you do the final fit.