Jump to content
Maestronet Forums

PROJECTING STRING HEIGHT TO BRIDGE


Scott S
 Share

Recommended Posts

I have one cello and four violin bridges to fit, good opportunity to change my technique. Currently, I set calipers, mark and nick the bridge top, string up the E and G strings, measure string height at fingerboard end, use this measurement plus some to mark and draw prefered radius on bridge, shape bridge radius and replace nicks. After this first shaping of the bridge top I then re-measure and re-shape once, maybe twice, more.

How do other people do this? I would like to change my technique to do one precise shaping of the bridge top. I have contimplated using nylon thread and spacer blocks on the end of the fingerboard. What techniques work using only two hands?

Scott

PS I absolutely refuse to discuss fitting bridge feet, especially with Burgess.

Link to comment
Share on other sites

To mark preliminary string heights on a bridge after the feet fit the top, I use a little wooden stick a bit shorter that the string length. The stick's rectangular cross-section measures 11 by 7 millimeters. These dimensions are double the string heights that I want to mark on the bridge -- 5.5 and 3.5 millimeters for the G and E strings, respectively, for full-size violins. A small sharpened spike protrudes from the center of one end of the stick, making the point of the spike 5.5 millimeters from the short sides of the end of the stick and 3.5 millimeters from the long sides.

To mark the E string side of the bridge, I hold the bridge in position on the top of the instrument with one hand, lay one of the stick's 11 millimeter faces on the E string side of the fingerboard with my other hand and make a little prick mark with the spike on the E string side of the bridge. Then I rotate the stick so that one of its 7 millimeter faces is sitting on on G string side of the fingerboard and make another mark on the bridge for the G string location.

After the G and E string locations are marked on the bridge in this manner, I lay my bridge curve template on the bridge and use it to trace a pencil line a little above the marks. With a knife I quickly cut away the wood above the line, mark the preliminary G and E string locations on the top of the bridge with a bridge string-spacing marking tool that I made from scraper stock and file preliminary string grooves at the marks. Then I mount a taipliece, G and E strings and the bridge. The strings will be a bit high, so I remove the bridge and file the grooves deeper until the string heights are where I want them.

After the G and E string grooves are the right height, I trace the final bridge height line with the template at the height of the grooves and remove the excess wood above the line with knife and file to achieve the finished bridge height. Then I mark the D and A string locations with the bridge string-spacing marker and file grooves for these strings.

It takes longer to explain it than it does to do it.

I made the bridge marking stick to indicate full-size violin string heights, but I also use it for smaller violins and any size violas and cellos. When using it with different sized instruments, I place my template on the bridge a bit higher or lower than the marks on the bridge, as required. The bridge string-spacing marking tool only works for full-size violin bridges so I use dividers to mark the string spacings on other bridges.

When I made the spiked bridge marking stick, I figured that it would be easier to put the spike in one end then plane the stick to 11 by 7 millimeters with the spike centered than it would by to first plane the stick to 11 by 7 and then try to get the spike in the exact center.

Though it's a bit complicated to explain them in words, these tools are very simple. I will try to put up pictures of them tomorrow.

Link to comment
Share on other sites

For violin I simply lay a sharp pencil on the fingerboard, and draw the profile on the bridge by simply moving the pencil across the fingerboard. Most pencils are 7mm in diameter, ie the tip of the pencil would be approximately 3.5mm. That sets the height of the E-string. For G-string just add 2mm from the profile, then use a nice bridge template to join this two points (E and G) together.

Link to comment
Share on other sites

i use one of many old used bridges, string up and measure how far off the strings are from 5.5mm for g and about 4mm for e, then i hold the used bridge against the new bridge, off set at the feet by exactly the amount, left and right, it was off from being the right height with the used bridge, then put a knife mark at the g and e spot at the top(on the new bridge). then line up my curve template 42mm radius with the two notches and gently score a line with the knife, etc etc i think this is a little/ simpler than above :unsure:

Link to comment
Share on other sites

I use something similar to Brad, with the following differences:

All four sides of the stick are different heights, with one side for violin E, another for the G; one for viola A, and another for the C. I have a separate one for cello, but one could make a six sided stick....

The other difference is that rather than a spike, I drilled the end to accept the cartridge from a cheap Bic ball-point pen. That's probably more trouble than it's worth, because sometimes you need to scribble on a piece of paper to get the pen working, but it makes it easy to draw a short ark at the string positions which can later be intersected with your string spacing, rather than needing to stab the bridge at the correct point.

I drilled the hole for the pen (spike) first, and then planed the sides to set the correct height, using a standard finished bridge as a guide rather than calculating, or trying to drill the hole in precisely the right place. This just seemed like a faster way to do it. The tool is only a rough guide though. Instruments flex to varying degrees once string tension is applied.

Link to comment
Share on other sites

Here's the spiked stick bridge marker. Mine is about 10 1/2 inches long. A visiting luthier recently suggested to me that this tool could be made to indicate 4 different string heights by installing the spike off-center just as David does. But then I would have to pay attention to which side was which. Instead, I just draw the preliminary bridge curve line a bit above the stab marks for violas and cellos.

post-4504-0-00061700-1295011111_thumb.jpg

Link to comment
Share on other sites

....it makes it easy to draw a short ark at the string positions which can later be intersected with your string spacing, rather than needing to stab the bridge at the correct point....

I figure that I've done enough violin bridges to be able to stab the bridge at close enough to the right points to be able to establish a preliminary bridge height. Since I make the preliminary height about a millimeter too high and achieve the final height by measuring with strings on and filing the grooves deeper as need, it doesn't matter if I don't stab the bridge at exactly the right points.

On the other hand, I haven't done enough cello bridges to use the same process. Instead, I first mark a cello bridge with two vertical pencil lines to show the C-A string spacing then stab the lines to indicate the preliminary heights. Since cello string heights are higher than on violin, and my marking stick is calibrated for violin, I draw my preliminary cello bridge height line about 3-4 millimeters above the stab marks.

Link to comment
Share on other sites

The stick's rectangular cross-section measures 11 by 7 millimeters. These dimensions are double the string heights that I want to mark on the bridge -- 5.5 and 3.5 millimeters for the G and E strings, respectively, for full-size violins. A small sharpened spike protrudes from the center of one end of the stick, making the point of the spike 5.5 millimeters from the short sides of the end of the stick and 3.5 millimeters from the long sides.

Though it's a bit complicated to explain them in words, these tools are very simple. I will try to put up pictures of them tomorrow.

I like your doubling up of the stick! ;)

I think this web-page might be helpful.

www.andrewcarruthers.com

Stick

David ... for some reason it doesn't surprise me that you took it to a new level! :rolleyes: :rolleyes: :rolleyes:

Brad I take it that you then space your strings on center, that is with equal spacing from the center to center of each string, and not with equal spacing between strings. :unsure:

Link to comment
Share on other sites

Here is my lame contribution to this high tech discussion. Simple sticks with one height on each end. They were prepared by adapting the height on a finished bridge, strung up to pitch on the instrument.

The ends of the sticks taper back to allow the upper edge of the gauge to come into full contact with the chest of the bridge. I usually trace a line with a sharp or fine lead pencil and then trace my curve. I cut away wood slightly above the line.

Photos two and three show the e string end and the g-string end that follow the bridge curve.

Bruce

post-29446-0-50282000-1295028575_thumb.jpg post-29446-0-79007400-1295029099_thumb.jpg post-29446-0-52171200-1295029110_thumb.jpg

Link to comment
Share on other sites

....Brad I take it that you then space your strings on center, that is with equal spacing from the center to center of each string, and not with equal spacing between strings.

It depends on where I filed the points on the bridge/nut string-spacing marker. And I made the thing so long ago that I don't remember which way I spaced the strings.

Link to comment
Share on other sites

....Simple sticks with one height on each end....

I made one of these before I got the spiked stick idea. I found that using it required three hands: one to hold the stick on the fingerboard, one to hold the bridge on the top of the instrument and one to draw the pencil marks. How do you do it?

Link to comment
Share on other sites

I do something similar to the pencil on the fingerboard method. However, the pencil I use, I planed half the pencil away to a half round cross section, so when you lay the flat side on the fingerboard, you can draw an arc on the bridge exactly the fingerboard height. It's just a simple matter to mark the G and E to the desired height above this line, and then draw the arc between them for the final shape to be trimmed to.

Link to comment
Share on other sites

I made one of these before I got the spiked stick idea. I found that using it required three hands: one to hold the stick on the fingerboard, one to hold the bridge on the top of the instrument and one to draw the pencil marks. How do you do it?

I have a clip to hold the bridge in place.

It's just a piece of hanger wire, bent to a squarish looking C shape, with a slot on one end for the crest of the bridge and a rounded piece on the other so it won't damage the inside of the table. I can bend the clip to get enough tension to hold the bridge up in place while I mark, or even while I set a neck etc. The small rounded end of the clip is slipped in through the f-hole and rests on the inside of the belly under the bridge and the slot is positioned in the center of the bridge crest. Works great.

Bruce

Link to comment
Share on other sites

....a piece of hanger wire, bent to a squarish looking C shape, with a slot on one end for the crest of the bridge and a rounded piece on the other so it won't damage the inside of the table....

Oh yes, these are shown in the Weisshaar book. I made one many years ago and never found it convenient to use. Maybe I didn't make it right.

Link to comment
Share on other sites

I made one of these before I got the spiked stick idea. I found that using it required three hands: one to hold the stick on the fingerboard, one to hold the bridge on the top of the instrument and one to draw the pencil marks. How do you do it?

Actually 5 hands ....an extra 2 to pull the elastic bands! :blink:

Another view.

Thanks Russell Hopper

Link to comment
Share on other sites

I always fit a bridge with it held up with two pieces of fine nylon thread - from the pin to the pegs - nicked into the bridge top at their proper locations, treble side, bass side.

So I can always see what I have at the board end under the string. I just drop the bridge to suit.

I can also set the clearances under the strings at the nut pretty close. Once treble and bass side is more or less right, I check the bridge top profile and string up properly for final adjustments for clearances and top radius.

Geoff

Link to comment
Share on other sites

Actually 5 hands ....an extra 2 to pull the elastic bands! :blink:

Isn't that just one elastic band? Maybe there's a knot underneath. It doesn't seem to be very easy to control the stop length.

I like the bridge clip because I can use it for so many different operations.

Determining the exact bridge position before fitting starts.

How much wood to take off the feet and where (roughing out only); especially handy if the arching is somewhat deformed.

Marking initial string heights; before the strings are up.

Alignment while preparing and gluing fingerboards.

Neck alignment and fingerboard projection height while setting or gluing a neck.

Positioning a new bassbar; I always do this once I have first determined the bridge position and together with the bridge I intend to use on that particular instrument. (Probably not necessary if you are making new symmetrical instruments. Restorers always do everything backwards. :lol: )

Bruce

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.



×
×
  • Create New...