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Thread: vintage mandolin bridge replacement

  1. #1
    Registered User mandosonthemarsh's Avatar
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    Default vintage mandolin bridge replacement

    I have a 1926 Brazilian rosewood oval hole Martin mandolin. I have been sanding the fixed original bridge to lower the action. It is very small and have been wondering if I replace it with a fixed classic model, how that affect the sound quality. The one I have on there is so skinny and small I am wondering if the larger one would be able to transfer more tone. I have seen many flat bottom bridges on line which might work. Also I am wondering about the difference between ebony and rosewood bridges, and where to buy a quality one without breaking the bank. Thanks, Bruce.

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    Café habitué Paul Hostetter's Avatar
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    Default Re: vintage mandolin bridge replacement

    When a bridge is that small, the difference between those two materials is almost insignificant. I'd always opt for ebony though. The important thing to remember on even a little slip of a bridge like that is to have as tight a fit to the top as possible. The mass of the bridge is not nearly as important as the fit. I doubt there's a blank worth buying—you have to make one from scratch if you've gone too far with the original. Fit the base first, then take the top down and make it all nice. And keep it as close to the original was as possible.
    .
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  3. #3

    Default Re: vintage mandolin bridge replacement

    Reviving this "zombie" thread because I have a Martin Model "C" mandolin with action that is a little too high. The neck is straight. The base of the bridge is rather thin, and I don't want to damage the original bridge. Would it be unreasonable to make a replacement bridge myself? I'm handy with small machining operations (dentist!).
    Any advice will be most appreciated.Click image for larger version. 

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    Steve

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    Default Re: vintage mandolin bridge replacement

    .. duplicate post. please delete.

  5. #5
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    Default Re: vintage mandolin bridge replacement

    By all means, feel free to make another bridge for your style C if you wish. Be sure to keep the original.

    And you are correct, you want to avoid removing material from the base of the original bridge. The one exception might be the strategic removal of a few thousandths of material if it is poorly fitted. But if you're going to make a replica, you might as well leave the original alone.

    It's probably best to rough fit what will be the base of the bridge to the top before you start carving away everything that doesn't look like a style C bridge.

    I made a bridge for a style C out of Sambar stag horn, which is similar in density to elephant ivory. It took about three hours with hand tools, plus a little while to fit it so that the ends would touch the top. On that instrument, the deer ivory bridge sounds noticeably different from its original ebony bridge. I like the ivory bridge better.

    If I remember correctly, some of the tools I used were various X-acto needle files, a round file, a small flat file, a couple of small sanding blocks, and a razor saw. If you are a dentist, I'm sure some of your rotary bits will be useful.

    To address the now ancient original post, I'm pretty sure that an ebony bridge was standard on all Martin flatbacks in the 1920's except for style E, which was ivory.
    Rosewood might sound a bit different. Some of that depends on the piece of rosewood and the way a particular mandolin might respond to it.
    The size, shape, and thickness of a bridge can have some effect on the sound, just as it does on a violin.

  6. #6

    Default Re: vintage mandolin bridge replacement

    rcc56, thanks very much for that prompt reply!
    I was pretty sure making a new bridge wouldn't hurt anything as long as I didn't damage the original. This is a very sweet-sounding mandolin which I got from my father. I've had it since the early '70s... I built the case over 40 years ago when I should have been studying for final exams! I want the action to be lower because I have a touch of arthritis in my old (71) age.

    I figured I'd start with ebony since that's what the original is made of. Can you point me to a good source of wood? I found a place( https://www.bellforestproducts.com/gaboon-ebony/) where I could get a 3/4" x 3/4" x 6" piece of Gaboon ebony for $3.50 but shipping is over $9.00. Heck, I guess that's not too outrageous... I wouldn't bat an eye if the prices were reversed.

    Also I wonder if there is a guide somewhere (video or text) explaining how to construct a bridge. I feel comfortable tackling the construction itself, but wonder about how high to make it. I plan to put a straightedge on the fingerboard and see where it projects onto the existing bridge, then measure the distance from that point up to where the strings sit. That will give be an idea of how much shorter the new bridge needs to be. I'm sure there are more details to it though.

    Thanks for any information you can provide or point me to!
    Steve

    Heh... I have discovered your web site and am looking for relevant information. And I *do* say "no" to crack!
    Steve

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    Default Re: vintage mandolin bridge replacement

    Steve if you measure the string height at the 12 fret, top of fret to bottom of string. Now how much do you want to lower it? If you lower it 1/32" you will have to make your bridge 2/32" shorter to achieve that. If you make the intonation adjustments on the top of the bridge too wide you can then you can string it up and fine tune the intonation on each set of strings so it plays in tune.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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  9. #8
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    Default Re: vintage mandolin bridge replacement

    If there is a Woodcraft store anywhere near you, they usually have a few chunks of ebony in stock.
    Or if there is a guitar maker or a repairman who makes guitar bridges near you, they might have some scrap big enough for your needs.
    If that fails, find out if there is a hardwood supplier in your area.
    Or you can order an acoustic guitar bridge blank from Luthier's Mercantile and see if they have anything else you need to help justify the shipping costs.

    When I make a mandolin bridge, the first thing I do is to thin the blank to just over finish thickness. Then I start carving away. For a flat top bridge, I rough fit the bottom to the mandolin before I carve the feet. For a Gibson style bridge, I carve the feet before I fit the bottom.

    Nearly all ebony these days has streaks in it. That's no problem, but if you want the bridge to be pure black, you can dye it with leather dye. Let it dry well and clean up the bottom before you put it on the mandolin so it doesn't stain the top.

    I do not have a website. I have a second or third cousin with the same name as me, and I see that he has a website. I have never met him.

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  11. #9

    Default Re: vintage mandolin bridge replacement

    Steve, you can’t go wrong. Just make your measurement with full string tension first, and don’t forget to keep your mask on. Ebony dust should be less toxic than rosewood, but no need to experiment. On the mechanical side, these very minimal bridges are not strong as beams, so nearly all the load on the top is directly under the strings, so can’t imagine that fitting the far ends is critical, but they should at least leave no visible gaps. When re-installing, just make sure that when you tension up that you don’t make the bridge lean forward from string friction.

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  13. #10

    Default Re: vintage mandolin bridge replacement

    Quote Originally Posted by rcc56 View Post
    I do not have a website. I have a second or third cousin with the same name as me, and I see that he has a website. I have never met him.
    Sorry... my confusion. I clicked on Paul Hostetter's link in an earlier post and somehow thought it was yours. Some good information there though!

    Thanks to you and the others who responded. It's going to take me some time to work on this project, but I will be sure to post a report with images. :-)
    Steve

  14. #11

    Default Re: vintage mandolin bridge replacement

    I have made some preliminary measurements.
    First off, the fingerboard isn't *quite* straight. There is a gap of about 0.25mm (0.010") between the G string and the fret in the middle of the fingerboard (at about fret 10).
    A straightedge laid along the fingerboard between the two G strings intersects the bridge about 3.5mm (0.138", a bit over 1/8") above the top of the instrument.
    The distance between the 12th fret and the G string is 2.35mm (0.093").
    The strings currently sit about 8mm (0.315") above the top of the instrument.
    So my first estimate at the bridge height I would be shooting for is about 7mm (0.275").
    Does this sound reasonable?
    Sorry for the metrics and thousandths of inches!
    Steve

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    Default Re: vintage mandolin bridge replacement

    0.010" of relief at the 10th fret is not bad for a 90+ year old Martin mandolin.

    I generally shoot for between 4/64" to a maximum of 5/64" [.062" to .078"] between the 12th fret and the bottom of the G string on this type of mandolin.
    Since the current distance is .093", you will need to reduce that distance by perhaps .020" to start with. To do that, you will have reduce your current bridge height by twice that distance, or .040", so yes, a minimum of 0.275" for the height of the new bridge is a good place to start.

    When in doubt, leave it a little bit high. It's easier to reduce the bridge height than to have to make a second one because you cut the first one too low. Most of the time, I reduce the height of a solid mandolin bridge from the top, and reshape it as necessary to make it look right.

    Good luck. If you get it right the first time, go to the head of the class. If you mess one up and have to do it over, it is no great sin. We all make mistakes, and you will have learned something and kept yourself out of trouble during these difficult times.

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  17. #13

    Default Re: vintage mandolin bridge replacement

    Quote Originally Posted by rcc56 View Post
    If there is a Woodcraft store anywhere near you, they usually have a few chunks of ebony in stock.
    Thanks for the Woodcraft recommendation. I found the necessary wood, and shipping is much more reasonable. Now I'm thinking about tools. I have a coping saw, but I'm looking at a small powered scroll saw and wondering if it would be a good addition to my collection. I like tools!
    Steve

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    Default Re: vintage mandolin bridge replacement

    I have made several bridges like you are going to make. I do them all with hand tools. I am not saying to not buy the scroll saw, but I wouldn't use it for this purpose. A small hand saw and chisels are mostly what I use. A block plane to start, but to shape mostly the hand saw and chisels. You might find a scraper useful too.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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  20. #15

    Default Re: vintage mandolin bridge replacement

    Steve, if you intend more small-scale hobby work and want sort of dental nostalgia, buy a Foredom rotary tool and shaft. It’s much more expensive than a Dremel, but both items are useful in shaping little pieces of wood, like, e.g. a bridge. An assortment of small files including some jeweler’s ones is helpful. A small pane of glass and some varied sandpaper grits is all you need for making things smooth and flat. In addition to a coping saw, a small handsaw, especially of the variety called a Japanese pull-saw, allows for longer and accurate straight cuts, as in cutting that block of ebony to size. A decent pocket or fixed blade knife rounds out the initial collection.
    If you want to get involved with chisels and planes, I’m afraid you need to take the graduate courses. There’s also a whole topic called vises…

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  22. #16
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    Default Re: vintage mandolin bridge replacement

    FYI. Here’s a web site I stumbled upon which has some good info about making bridges for vintage bowl-backs and flat tops :

    http://www.mandolinluthier.com/Hbridge_building.htm

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  24. #17

    Default Re: vintage mandolin bridge replacement

    Well, I have received the ebony wood for the new bridge. It's in a 1" x 1" x 6" chunk. For some reason (moisture resistance, I suppose) it's coated in wax.
    I have a new package of 6 blades for my coping saw, which I think will be adequate for roughing out the bridge. I will post my progress as time goes by.
    Click image for larger version. 

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    Steve

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