Bridge profile Options

[DougP]

When planing bridges, what should the profile be for the front of the bridge. I know that a good bridge is shaped somewhat like a scallop shell, with more wood taken off the corners of the top. Exactly where should the taper or roundness begin? Should the taper start at the foot, or higher up on the bridge?

[Michael Darnton]

I plane the front and the back (much less than the front) from about the waist up, in almost straight radiating lines from the waist up, as if you took a collapsible fan, opened it, and pushed the top edge into the line you wanted. In order to keep these lines from looking concave, they're actually just a bit convex, but not much. This leaves a facet line at the waist, which I then blend in. When you get done, looking at the bridge from both the side and from the top, the top edge should appear as a straight line.

That's how I do it, anyway.

The more belly you have, the more nasal and less open the sound.



The trick is to make it look like you haven't done anything--that you got from here to here without anything happening that anyone notices. That's what del Gesu does with his top arches, too, by the way--up from the edge to the peak of the arch and back down again without any apparent curves except right across the center. [This is a thicker bridge than I normally make, for a tonal adjustment, but the principle is the same for it.]

[HongDa]

Once I have my bridge to thickness, feet fit and hight and curvature established, I then use a knife to make the thickness of the top to about 2 mm. I then file that to a clean champher or facet--filing from one side to the other in clean motions.
I then make the side profile straight from the corner of the top down to the corner of the foot---removing a hair of wood down at the foot so it's bottom profile is slightly curved.
At this point there are now one facet on each side and one along the top of the crown. Now everything between has to be blended into those established edges to give it a nice , as you say -scallop shell appearance.
I was taught to take 2/3 off the front and 1/3 off the back so I do the same thing slightly on the back but this is a very minute amount of wood and so only the upper area has a slight curve to it if you lay a straight edge along it.

[Jeffrey Holmes]

My feeling is that bridges are a game flexibility, mass, and how (where) mass is distributed. I tend to shape the front of my bridges similar to the way Michael does to start with, but leave a slight "chest" that has it's apex at about the heart level on the front. I agree about the "belly". If the apex is too low, strange things seem to happen to the sound. I make the front of the bridge slightly curved from side to side, waist up... and this leaves the edge taper *appearing* pretty much straight (the chest is over the heart, not at the edge). This allows me to make the edges of the bridge look "lighter" while still keeping enough mass in the center. I use the kidneys (or eyes, if you prefer), ankles and lower arch to adjust the sound, depending on the fiddle. The back of the bridge starts out flat, but I relieve the upper portion (1/4 to 1/3) slightly... a very small amount more on the e side than the g side.

[Oded Kishony]

Jeff, Michael, etc.

What are you using to finish the surface of the bridge? Sandpaper, file, do you burnish the surface?
What are you using to blend surfaces after you've (I assume) planed them?

Oded

[Michael Darnton]

I just started, after years of sanding up through grades, scraping and going directly to 400-grit paper.

Another view. How does this compare to yours, Jeffrey?

[DougP]

Thanks to all of you. Exactly what I was looking for. Beautiful work, Michael. I arrived by trial and error close to what it should be, but that was the finishing touch. Time to get the plane out again.

[Jeffrey Holmes]

Hi Michael;

Yup. That's what I was talking about. My cello bridges are even more curved (in relation to their size)... and I extend the arch down the outside of the leg to just above the ankle.

Oded; I use files for shape and finish. I file across the grain (from the feet toward the top). A sharp fine file gives a burnished look to the surface. Just personal taste/technique, but a half way shiny (burnished) surface is easier for me to see when I bounce light off it from my overhead lamp (I catch irregularities in the surface shape more easily).

[Michael Darnton]

By the way, I cropped the top picture exactly parallel with the edge. If you put a square piece of paper on your screen, with one edge on the bottom of the photo, and compare the front and the back of the bridges against this "square" you can see how much "back tilt" I use. I don't think it's obcious there, either, by eye, exactly what's going on.

[BarryD]

What process do you use to establish the bridge height?

[ctviolin]

Aren't you pretty much stuck using the string height above the fingerboard for establishing bridge height?

[Michael Darnton]

Somewhere towards the middle of the process, I put on the strings after setting a preliminary height, then file the E and G grooves until those strings are the right height, remove the bridge, contour the top based on those grooves, and then finish the bridge.

[DarylG]

I do what Michael says for the final height. To find the preliminary height I use a 6" metal ruler held against the f-board, while holding the bridge in place, and poke the bridge with the edge of the ruler. Then measure up and trace my template. I can usually get it quite close to the final measurement.

[Brad Dorsey]

I have simple gadget for determing the preliminary bridge height. It is a straight maple stick whose length is a bit shorter than the distance from the nut to the bridge. It is rectangular in cross section with the ends measuring 7 by 11 millimeters. These dimensions are double my desired string heights of 3.5 mm (E) and 5.5 mm (G). There is a sharp metal point protruding from the exact center of one end. To use it, after fitting the bridge feet I hold the bridge in position, lay my gadget flat on the E string side of the fingerboard and mark the E side of the bridge. Then I lay the gadget on edge on the G string side of the fingerboard and mark the G side of the bridge. My gadget works the same as what you do with your ruler, but I don't have to measure up from the mark.

[Michael Darnton]

I use a pencil. It lays a line 3.5mm up across the whole front of the bridge as I sweep it across the end of the board, and then I mark up 2mm more for the G string. I cut my preliminary shape just above those points.

[DarylG]

Thanks Brad, very clever. I might have to make one. I'd be interested in hearing what measurements others are using for string heights. I use 5.0mm(G) and 3.8mm(E) for a standard setup with synthetic strings.

[kraut]

I use a blued-steel saxophone needle spring on my maple stick. It works great to give preliminary points for my bridge template. I think that my resuls are consistent this way. You just have to make sure that the fingerboard is fairly flat, especially on cello. A fingerboard that dips at the end presents problems with this method.

[HongDa]

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I use the kidneys (or eyes, if you prefer), ankles and lower arch to adjust the sound, depending on the fiddle.

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I'd like to know if most of you here work with a standard cut and then work down from there for adjusting the sound---and what that standard cut would be.
From my small selection of bridges I have to work from it seems the waist is normally about 16mm,the ankles about 4mm,legs 5.5mm, and section between the kidneys and heart(arms?)--about 5.5mm. I also find with a straight edge placed at the top of the kidneys the distance between that and the bottom of the heart is about 1-1.5mm.And finally the bottom of the heart down to the arch is usually 13mm.
Do you all pay a lot of attention to these measurements?
The problem I always have is getting the arms to the width I want while at the same time accomplishing a nice looking shape to the kidney…., any advice on this?

[Jeffrey Holmes]

Quote:

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The problem I always have is getting the arms to the width I want while at the same time accomplishing a nice looking shape to the kidney…., any advice on this?

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Shape and size of the arms has quite a bit to do with how much and where you take wood from the outer curve of the kidney... If you just cut them down without adjusting these curves, the kidney shape can get rather strange.

Michael had a nice shot of a bridge in progress he posyed a while back. Still got that around, Michael?

[HongDa]

[quote
Shape and size of the arms has quite a bit to do with how much and where you take wood from the outer curve of the kidney... If you just cut them down without adjusting these curves, the kidney shape can get rather strange.

Michael had a nice shot of a bridge in progress he posyed a while back. Still got that around, Michael?

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Over time I have come to realize how these outer curves influence the shape.Lately I have found if I do some initial trimming of these outer curves and try to bring them more upwards and then trim the arms into them-things work better and look better. where do you usually begin your trimming Jeffrey? I guess it has alot to do with the bridge blank?
I hope to see Michael's other bridge photo.
I also took some shots of some shop bridges I have and will post those for anyone's interest.