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I have an Epiphone that came stock with a wooden bridge base and tune-o-matic top. This factory bridge has a perfect fit to the top of my guitar, but the posts are too tall so I've decided to switch to an all rosewood bridge from Allparts. Unfortunately the Allparts bridge was very flat on the bottom and has required a lot of fitting (sanding) so far to match the top. I've done the usual procedure: tape a piece of sandpaper to the top and take material away from bridge base by sanding front to back until it matches the top. I am doing this by hand with no bridge fixture/jig and I have it fitting the top really well except for maybe 2-3mm at each end which are ever so slightly not touching the top. I would say at this point 95% of the bridge is making good contact with the top. As a comparison, if I take the factory bridge and line it up on the top and press down it's difficult to turn whereas if I take the "fitted" Allparts bridge, line it up, and press down it more easily turns.
The thing is that since I'm doing this by hand, it's difficult for me to keep the bridge perfectly straight when sanding making it difficult to get a perfectly uniform shape of the top to the bridge. I know a lot here fit bridges by hand, but I don't see this mentioned here ever which makes me think this may be a minor thing to be worried about, but at the same time I don't want to put my guitar all the way back together again to find I needed to do more work to the bridge. I am also not super fond of the idea of spending $75 to get a jig just for this purpose. If this were a nicer instrument I'd take it to a luthier, but since it's an Epiphone I don't want to spend the $$ for that level of work.
Thanks for any inputs ahead of time.
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10-22-2024 07:42 AM
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I could have done a better job with mine. I can get an envelope under the edges(the feet outside the bridge), and also under the E and A strings.
The process wasn't going well for me, but I decided it was better than it was, slapped it back together. Then I never went back to touch it up. I've been meaning to go to a wooden bridge and I'll probably just pay someone to fit it. I've done about 20 gigs with the guitar this year, so even though it's an Epiphone, it deserves some care. And I can finance the upgrade with gig money.
Someone "upgraded" the bridge before the guitar got to me, it wasn't fitted at all, which is why I tried to fix it and then decided it was better than before.
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Does it sound OK that way? I'm assuming it does if you've gigged with it. I'd say my bridge is fitting about the same as yours from how you describe it. I'm kind of tired of sanding the bridge base and don't think I can get it much better.
Originally Posted by AllanAllen
Also, could I ask what grits you used? Mine needed a lot of work so I started with 80 and am now at 150. Was going to finish up at 220 and call it good.
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I used whatever was in the garage, and I only used one grit since my plan was to go back and do more work.
It sounds fine to me, there are tons of clips of me playing it on the forum. Check the Dexterity thread for unplugged or the Showcase Subform for live sound.
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FWIW, I understand that many like to have the underside of the base (bridge) just a bit more arched than the top is (without strings on it). This as the case with my original Loar bridge and may be the case with your original bridge too: I would definitely expect that to explain the "harder to turn" observation. Originally Posted by chris32895
If also put on an Allparts bridge (but the ebony variant) on my Loar, which I shortened by about 1cm on each side and sanded down the top of to make it match the original bridge more closely in footprint area and weight. I too found that the mating procedure was a lot more work than I expected. Could be because it was the 1st time I did it and I didn't dare to press down enough ... but it was already tricky enough to keep the sandpaper fixed to the top. I called it quits when the match seemed to be completed but I have the same kind of gap at the ends as you describe (and mine also moves more easily than the stock bridge).
I think you should string the instrument up. The pressure from a typical set of archtop strings is probably a lot more than you'll try to put on my hand and with the compression of the top that gives your bas might well make full contact. If not shouldn't matter much; it would correspond to making a tiny reduction to the base width that ought to be negligible given how wide it is (if you have the same item as I).
Do you even play that guitar acoustically in a way where you need the maximum energy transfer into the top?
A simple but somewhat crude way to fix "end gaps": use a thin piece of paper or a feeler gauge to mark the place where full enough contact is achieved, and saw off the excess "overhang". It's much easier to file and sand down the ends to something nice and thin than it is to mate the base to the top, and the reduced weight will only benefit the acoustic response.
EDIT: I used 80 grit too. When done I used one of those 3-grit nailbuffer "sponges" to smooth the bottom. You probably don't want it too smooth anyway as a "textured" underside will help it remain in place better (the underside of my stock bridge wasn't perfectly smooth either).
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BTW, "the posts are too tall" on the stock bridge? You mean the 2 metal bolts that hold the saddle in place? You should be able to unscrew them from the base and then shorten them as much as you want!
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I use carbon paper not sandpaper taped to the top.
I rub it just a little, then scrape off the carbon rubbing till the carbon rubbing is even across the bridge. This may take many rubbings.
You are now done with a perfect fit.
I learned this procedure watching machinist scrape fitting large metal parts.
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Based on the input I will sand to 220 then and call it good.
I could just snip the posts, but I want to change from a tune-o-matic to a rosewood bridge. The Allparts rosewood top does technically fit the factory bridge base, but the posts are narrower than the posts on the Allparts bridge and so don't fit quite as snuggly as I'd like. Once I'm done I essentially have a tune-o-matic bridge and rosewood bridge I can swap out if I wish. Originally Posted by RJVB
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This is the current set up on my German Fasan. It was like this when I bought it. The guitar sounds really nice as it is. Hopefully when I get round to sorting it, it'll be even better. Who knows?!
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The floating bridge foot is meant to be coupled with the top. While anything can work, including just sawing off the legs of the feet where there is no contact, a properly fitted bridge foot and top does give a more solid transmission of the sound energy, assures a real solidity of the vibration and especially in a solid topped instrument, can have a profound effect on the way a guitar feels and sounds.
In his last period of his life, Jimmy D'Aquisto believed that the bridge had a huge shaping effect of a guitar's sound. He'd craft a bridge, sometimes more than one and/or more than one tailpiece to offer a player the ability to match their playing with their guitar.
In truth, if you're mainly concerned with just having a working guitar, and you've never compared your guitar A/B with a poorly fitted and properly fitted bridge, live in bliss and don't worry.
If you can feel the subtlety in attack, decay and sustain that comes from a well tuned system, then yeah, it does make a difference. That's a vibrating interface between the energy of string vibration and the task of transmitting that amount of energy to a moving top. Any sloppy edges are just going to detract from the ideal of a seamless transmission of energy.
Does it matter? Should you care? Will you play better? That's up to you. A car was designed and built to have perfect alignment between 4 wheels. One day an unfortunate encounter with a fire plug puts the chassis out 5 degrees. Does it make any difference when you're making your way to work everyday just fine?
Ask yourself. Ask your mechanic. Ask a luthier. It makes a difference to me, but that's just me.
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Cool! It's like a booster seat for a small child in a high chair, something to raise up the actual bridge to a height where you can play. I have a suspicion in the back of my mind that the top arching height sank over time and dropped the bridge too low (it happens) and someone gave it a "lift". Originally Posted by garybaldy
This is the current set up on my German Fasan. It was like this when I bought it. The guitar sounds really nice as it is. Hopefully when I get round to sorting it, it'll be even better. Who knows?!
Put this in the book of Interesting Solutions to Difficult Situations.
If it sounds good to you, let it inspire you. Happy playing!
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Dentists use the same technique after filling a tooth or installing a new crown/inlay! Originally Posted by BBGuitar
A more proper way to get a better rough match is to take a marker like a thin pencil or ballpoint recharge and a tiny round washer, stick the marker through the washer against the base put in the proper position, and trace the curve of the top onto the base. You can then use whatever powerful tools you have to remove the excess material from under the base.
Note that I only suggested that for negligibly small remaining, improperly matched bits. The Allparts base is big enough maybe even for an 18" top so removing some material from the ends should only be beneficial for a smaller top. Originally Posted by Jimmy blue note
Either way it's pretty certain that there's a principle of diminishing returns at play here!
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Good points. This is an Epiphone I paid a little over $600 for so I'm going to get it close then not worry and just practice. If it was an all carved instrument like the Eastman Pisano 880 model I had a couple years back I would be more inclined to take it to a luthier or at the very least get a jig to ensure the fit was as good as I could get it. I may just do it like this, live with it, and if so inclined later take it to a luthier.
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Will a poorly fit bridge slowly strain the top until it breaks one day? The pressure of a 5 degree bend in the chassis with unaligned wheels will cause some big problems down the line. Originally Posted by Jimmy blue note
I'm seriously asking the question.
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Chalk fitting a bridge foot is an art of great patience. If you're using the "tape the sandpaper to the top and sand it to fit" method, be careful not to rock the bridge or you'll wind up with an even worse non-flat surface. Patience. Originally Posted by RJVB
Diminishing returns? Like why buy another guitar when there's not enough time to practice on the ones already in the collection? Oh yeah! Wonky bridge. Sounds like a great excuse to buy another guitar with a solid bridge... just in case, ;-) Originally Posted by RJVB
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Thanks. I've had a good look at the top and, to me, it hasn't sunk. Now the neck is a different matter. High action needed to play! Originally Posted by Jimmy blue note
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I empathise ….
I ‘fitted’ my rosewood bridge to
my jazz box by eye and trial and error
a few years ago
the treble end is ‘flying’ a mm or so
but the rest of the base is now in good
contact with the top
it sounds good , doesn’t move
so yours is probably fine too
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No, as in why continue sanding and sanding to get the last fractional few % fitting perfectly and take the risk of ending up with a non-flat or skewed bottom if you can't hear the improvements anymore, for instance because the guitar isn't exactly a top-of-the-line instrument? Originally Posted by Jimmy blue note
Or, when does "better is the enemy of good" start to apply (valuable question my PhD directory taught me, if any) ?
When I did this operation myself I went to a local luthier's workshop because I don't have a proper workbench to do it, plus I wanted some guidance from an experience wood worker. We went to where sanding left more or less uniform traces of wood dust on the sandpaper and the fit looked good. What with the chatting it we must have spent about 2h to get to that point, so I put on the corresponding wood saddle and strung her up. It sounded at leat as good as with the stock saddle but realised quickly it didn't have enough radius so had made the instrument unplayable for me. Call me lazy for not reworking the ebony saddle but I simply decided to put on the rosewood-with-bone-insert saddle that I had bought to test how I'd like the sound with that. Easy call: I had access to a grinding wheel to take off the required amount of material from the bottom of the bone insert, and it already had an appropriate radius.
Turns out I actually prefer the sound overall, due to a probably better transmission of vibrations. I probably wouldn't have found that out anytime soon if I'd not been in a lazy hurry.
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I've always used a contour gauge to guide and check progress. These are inexpensive (about $10) simple devices with a line of sliding fingers in a row. Gently press one edge against the surface until the fingers all contact it. As they slide upward, you'll see the exact contour on the top and the bottom. Lay the contour against the rear face of the bridge and scribe or trace it on the side of the bridge with an easily visible marker. The front and back of the bridge will not be the same, so you need to trace both front and back faces separately. If one face is perfect but the other still needs some removal, you have to angle the bridge toward the side that needs more removal to get the best fit without removing more than necessary.
I use the bottom edge (the concave side) to mark the bridge, so that all of your markings will be removed when you're done. You can scribe a line along the top edge, but then that line will be higher than the limit of desired removal. If you prefer to do it that way, use a marker you can easily remove and stop when the bottom of the bridge is just at the marked line.
Use tape on the top and mark the exact starting location of the bridge, to be sure you're gauging the contour at the right spot for your intended bridge location. Locate the ends well side to side, and only move the bridge against the abrasive paper in line with the strings. If it's a new bridge, you won't know exactly where you want it for best intonation until you can fit it and check. But you'll be close enough to just angle the bridge a tiny bit and not need additional sanding in most cases. If you do need to sand more to accommodate the necessary angle,, hold the bridge at the angle you find best for intonation when doing the final few passes.
With this guide on each face, you know when you've reached your end point.
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JimmyBluenote put it well. In a nutshell, the better the contact at the base, the better the fit, the better the vibes transfer to the top. It's all one instrument.
First, protect your guitar's surface by taping a sheet of typing paper and masking over the ef-holes. Mark on the paper where the saddle will be close to intonation length
Relieve the middle of the bottom by using paper shims under 80 grit sand paper for initial sanding.
Remove the paper shims, then replace with 120 grit for final sanding. During both stages of sanding I keep the saddle on the base with a high E string wound up with just enough pressure to guide the bridge in line between the tailpiece and the nut, and it helps keep the bridge perpendicular to the surface.
(Because the middle is relieved by several thousandths of an inch, it makes sanding the ends easier.)
Continue to sand only until wood dust colors the sandpaper fully across the length of the bridge base.
Can't go wrong.
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I'll add that for me, once it looks like I've got a good fit across, I'll secure the bridge foot (vice is nice in this situation) and with a flat cabinet scraper or wide chisel add a slight concavity to the centre part of the base. This is just the smidge needed so the string pressure pushes the bridge snug against the top, gives the outer edge a seamless contact and allows for that fit to remain as seasonal change effects the height and curve of the arched top (these fickle archtops DO change seasonally, tho the degree depends on lots of things... not so much on a laminate).
It's a bit of an ordeal to get it right, but seriously, the time and effort you put in is a point of pride and a gesture of how much you put into what you do, and you'll know it every time you hold that guitar and play it.
Just a two cent thought.
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How much is a smidge? Originally Posted by Jimmy blue note
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According to the international standards of weights and measurements... Originally Posted by garybaldy
Less than a paper's thickness, enough to allow light through, and for that light to disappear when pressed. Just enough to assure that the strings will seal the interface rather than cause the ends to lift. Avoiding the base to be convex in any way is the name of the game.
Again, this is just what I strive for, and it seems to fit. For me.
In violin family lutherie, everything rests on two feet, that assures the greatest amount of movement along many axes. Some earlier luthiers used bridges with two feet, actually building an open space in the middle. Guitar lutherie is a relatively young art and it was Jimmy D'Aquisto who had an unquenchable thirst for innovation and understanding. He saw the bridge as an integral part of the top. On my own Jimmy D', the bridge is surprisingly thin, but the base is WIDE, and the transitions in depth are smooth. This was the way he saw ideal.
Either way, I believe that pressure at the outer edges of the bridge foot are more important than the centre pressure if the outer edges don't even have contact. But I am not but one person with my own notion about why and how things work.
I worked with a great luthier Al Carruth and he was CONSTANTLY evolving his designs. Low mass bridges, high mass bases that stored energy, archings, graduation depths changing with archings... it's all part of a system. One thing that was always a minus: Sloppy transitions and undefined edges. So when you see light at the edge of a bridge foot, some edge where the bridge goes from touching to space is not clearly defined. This means energy is sloppy at that transition point. Avoid that. It's just inefficient. There was a maxim: If it looks beautiful and has clean lines, it tends towards naturally clean sound. If you have a mug with wonky surfaces, it won't "ring" the way a beautifully crafted bone china cup will. Function follows design.
That slight smidge of light is to assure a better "seal" at the outer parts of the foot. Smooth and gradual transitions, defined edges.
In my narrow view of things anyway. I will never argue with someone else's success otherwise. I just try to understand how and why it is better.
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Hats off to Jimmy Bluenote!
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Ken Parker hollows out the inside center of his solid bridge. This makes sanding to a perfect fit easier.
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