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  • Bones 4:42PM
  • jpipper17 4:42PM

Techniques for hollowing out the bridge?

Have you guys tried making your own bridges? I would like to give it a shot but the process of hollowing out underneath is the only thing I am unsure about. I have already cracked one of my bridges(another one is on the way) while trying to modify it. I don't really want to repeat that, so I am wondering what methods people here are using. I have a couple dremel tools that I haven't touched in a while. Thinking the plunge router attachment with the right combination of bits might work. If anyone here has advice, I will listen to that first before rushing out to spend money! Thanks


  • Jeff MooreJeff Moore Minneapolis✭✭✭✭ Lebreton 2
    Sorry you haven't gotten an answer. It's perhaps prickly to try to suggest how to do this, but you want the lightest - stiffest bridge you can get. These two things are somewhat antagonistic.
    I've make a lot of bridges - traditional and not. I've experimented with super light and therefore weak bridges. They don't sound as strong and full as the stiff ones.

    The best thing I can offer is to make a simple clamp that holds the bridge up side down. Mine is nothing more than 2 peices of wood making a bridge sandwich with the actual bridge as the "meat" and the pieces as the bread. These are longer than the bridge and screwed lightly together with long screws. Then the sandwich is screwed down to a heavier piece.
    Because of the shape of a bridge, its only being clamped on the "feet". So this is a very low pressure clamp and the whole thing won't take much pushing and pulling of blades, but because a dremel doesn't have to exert much energy on the bridge, it makes a stable platform to abrade out some exess wood to lighten the bridge with better control than if I was just holding the bridge in one hand and a dremel in the other.

    Think of your little bridge like it's big cousin over the river. I don't know how to explain this but forces on any structure are resisted triangularly. So leave you bridge strong in all three dimensions by not disrupting the triangles in any dimension. Work only on the "inside" of the triangles leaving enough wall thickness as well.
    "We need a radical redistribution of wealth and power" MLK
  • Thanks! That does help a lot. I have been going over it in my head and I think I have come up with a jig that will do it on the drill press instead that might allow for more consistency. It will definitely be a learning experience. It is tempting to think about "how light can I make the bridge?" but I know that lighter doesn't necessarily mean 'more balanced'. So, it will be interesting trying to find where that line is. I am currently building an archtop, and have been going to Benedetto's book and video series for clarification whenever I need it. He says the same thing about carving the top plates, "the beginner/amateur thinks that the top needs to be carved as lightly as possible but the exact opposite is true. Only a top that is carefully graduated and properly braced will yield a clear, well-balanced tone" I am paraphrasing here, I don't have the book with me.
  • Craig BumgarnerCraig Bumgarner Drayden, MarylandVirtuoso Bumgarner S/N 001
    edited October 2017
    For what it is worth, I hollow my bridges out by hand with a Dremel. It is the last thing I do after the bridge has been fit, slotted and finalized in size and shape. I use three different bits. The first cuts are with a 1/8" spiral cut router bit combined with a Dremel router base to cut first a shallow trough in the under side, then a deeper ones. I vee this out with a conical bit and then finally get down deep in the center with a small bud bit. I free hand all of this. Free handing allows me a lot of flexibility in taking more here than there and more to one side than the other, following the slant of the top edge. BTW, I liked that picture of the little Dremel sanding drum for cleaning up the edges of the hollow, have to try that, but to get deeper, you need the bits.

    Regard bridge weight, I strongly believe that the lighter the better as long as structural integrity is kept in mind. I've never reached a point where a bridge collapsed or visually sagged under string tension. I have gotten the side walls so thin I could see light through in places (yikes, too thin :-), but the bridge still worked. I don't disagree with Jeff and others that a bridge can be too flexible, but I have not seen a Selmer style bridge of normal height (17-20mm) reach the point in spite of serious hollowing.

    A bridge contributes nothing to the stiffness of the top, so its effect is mass only and reducing mass in the top assembly without reducing stiffness almost always results in a livelier guitar that sounds better. I often get bridges down to 10-11 grams, but anything under 14g is generally okay. Above 14g, the effect on sound is very noticeable. I've replaced a couple bridges that were in the 25-30 gram range with 12g bridges and the result was nothing less than spectacular.

    BTW, watch out for the weight of mustaches. Thick ones out of ebony can weigh over 4g apiece. By using lighter wood and hollowing the undersides out, I get them down to ~ 1.5g each.

    Good fit to the top and shallow string notches are important.

    Regards the Bob Benedetto reference, while I can see what he is getting at, I'm not sure that what is true for archtop guitars is necessarily true for gypsy guitars as they are very different. In gypsy guitars, my experience is the reduction of mass in the top assembly is quite important and everything else being equal, less is more. Mass and stiffness are obviously related, Reducing mass without reducing stiffness is at the heart of a string instrument builders craft. There are many ways, old and new. Arched bracing combined with the pliage is a perfect example.
  • Thanks a lot, Craig! I am blown away by how people on this forum are always willing to share so much great, sometimes hard-won, information. It has made my transition into playing and being able to set up this type of guitar a lot smoother than it might have been. Very much appreciated.
    BucoJim Gallaher
  • Jeff MooreJeff Moore Minneapolis✭✭✭✭ Lebreton 2
    Joshi-m. For simplicity and just to quickly arrive at the best points of intonation and playability, I started making bridges that look like a bent stick of wood. Like a stick of wood with two feet and a overall C shape to carry the strings.
    Intonation and playability involve getting the saddles for each string arranged in all three dimensions, so by throwing bridge stiffness out the window, and just focusing on the geometry of saddle placement, I learned how to maximize intonation and playability.
    These bridges "worked". The guitars sound "ok", but I was playing live and plugged in so I could eq away most of deficiency, sort of.
    Later, I wanted to to build bridges that were easy to build, lighter than hell, yet still stiff enough not to loose "any" energy and transfer "all" the frequencies that a string produces to the top.
    These new bridges brought more life to my guitars than I expected. With only a simple balance scale to compare any two bridges and not even a conception of a way to measure "stiffness", I am confident about my results regarding intonation and playability - that i can make lighter bridges than what comes even on high end guitars, but quit worrying about exactly how "stiff" "perfectly stiff" is!
    I could visually see the twisting when I physically twisted my bent stick bridges. My aim in making bridges now is to just attempt to make them "perfectly stiff" whatever that means, yet confidently make them perfectly intoned and maximally playable, and we can all imagine what that means.
    What "perfectly stiff" means to me (without any real measurement) is that "no" vibration of the string is lost.
    Strings vibration in all three dimensions even trying to go in all directions at once. I want bridges that translate all of this (as if that were possible) to the top of the guitar. Maccaferri's bridge design is powerfully pyramidal in all three dimensions, so I make my un-scientifical reductions of bridge weight with that in mind to get a 'perfectly stiff" bridge.
    The result is that even marginal sounding guitars sound better, and my really nice guitar sounds terrific.
    I've no doubt most of us with the inclination can improve our bridges. I think the harder task (compared to reducing the weight of a bridge) is getting really good intonation and playability.
    Making a C shaped "stick" bridge blank on a jig saw takes a couple minutes. Finding exactly where all 6 saddle grooves belong on that stick takes a lot of trial and error till you get to a maximum point in the intonation and playability tradeoffs.
    "We need a radical redistribution of wealth and power" MLK
  • You bring up some really good points. Some really obvious ones that I have completely missed! I have been spending so much time thinking about how to make the guitars louder and more responsive but I have devoted very little time to think about the shape/arch and angle of the saddle. I suppose that is a whole other ball of wax to dive into now. I ordered a few cheap bridges from China just to see what you get. The first one showed up yesterday and it is mostly garbage, but, it might be good to hang on to and tinker with. Re-shape the saddle and see where I can take the guitars with regards to playability and comfort.

  • Jeff MooreJeff Moore Minneapolis✭✭✭✭ Lebreton 2
    Even if one's ideas aren't completely valid (mine), most guitars need work to get them to play well - a big advantage if one plays a lot. I focused in on making bridges because I want to keep the guitars I have running at a peak. My attempts at improving the sound of guitars ended at 0, so I can just buy a sound (the body) and get the feel and intonation at my leisure. I have a small shop and some jigs to make a bridge that'll work, quicker. I've bought chunk's of rosewood and can just whack off a block and go to work on it.
    Pleasure talking with you.
    I bet your efforts will pay off as you go!
    "We need a radical redistribution of wealth and power" MLK
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