Replies to This Discussion

Permalink Reply by Timothy Hunter on April 8, 2019 at 7:43am

its functional. the bridge rakes to get the intonation correct. the rake compensates for not only scale length but also string diameter. you roughly place the bridge at the scale length used. tune the string to pitch, then check the octave at the 12th fret. if it is sharp move bridge back a bit. then do the process over again. tune the string to pitch and check 12th fret again till its correct. do this on the 1st and 3rd strings and the bridge will naturally have a slight  "cockeyed" look. if you are using a solid 1 piece bridge like a bolt this is the best you can do. the middle string has to be what it is as you cant adjust it.  if you use a bridge with individual bridge pieces then you can get all 3 strings exact.

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Permalink Reply by KOOL DOG HOOCH on April 8, 2019 at 8:54am

Thanks for the reply. If I'm understanding this right, if each string height is adjustable, skewing the bridge is unnecessary? But moving the bridge forward or backwards may be?

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Permalink Reply by Taffy Evans on April 8, 2019 at 6:15pm

Hi Will, the bridge is set at an angle as explained for getting the correct length for each string.

On full size guitars the bridges are straight and the saddle only is angled to get correct string lengths.

Electric guitars normally have individual adjustable saddles and some acoustic guitars mandolins, and arch top guitars have wider saddles which are shaped so each string length is catered for.

The scewing of the bridge is done regardless of the adjustability of string height.

However the amount of scewing (compensation) is governed by string thickness and the string height (action) above the frets, normally measured at the 12th fret, sometimes at other frets.

Because all guitars, scale lengths, string compositions and other factors are different any "formula would put you "ball park", one normally fine tunes using a digital tuner. Plenty of info on here re doing that.

Taff

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Permalink Reply by KOOL DOG HOOCH on April 8, 2019 at 10:28pm

Is this what Stew Mac talking about using the fret calculator for 17 frets, 25.5 scale acoustic guitar. 

Bridge placement for 25.500" scale length

Distance indicated is from the fretboard edge of the nut, to the break-angle of the string at the peak of the saddle.  Treble "E" or 1st string: 25.589" (± 0.030") Bass "E" or 6th string: 25.715" (± 0.030")

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Permalink Reply by Taffy Evans on April 8, 2019 at 10:43pm

Yes that may be The measurements, but it still needs action height and string mass/diameter to be factored in for final fine tuning, as explained posts below.

I can't measure that small a number so I use my tuner and ears and eyes. Ha ha.

What you are compensating for is the different stretch rates of the different strings as you push them down to the fingerboard. If playing slide only you may not need to compensate as you are not fingering so not stretching the strings

Taff

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Permalink Reply by KOOL DOG HOOCH on April 9, 2019 at 5:16am

Thanks Taff, I have the means to, but not the intentions of getting that damn technical. I want it to sound right, but I'm also a "close enough it looks good from my house" type of person! Its a CBG not a handmade $2000 flat top! I'll dial it in with a tuner as best as I can and go from there. Thanks again for the advice.

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Permalink Reply by Daniel Walter on April 8, 2019 at 6:46pm

hi folks. good info, i get it. what i don't get is that the bridge i'm about to install has anchors, pieces that go into the wood. you know what i'm speaking of. drill large holes, sink these things in, then they accept the threads to hold the bridge. like many chrome tail pieces. so i recon ya gotta measure, then install. so moving the bridge around after is not an option. bothers me. many factory guitars use these mounting methods. so how do you know how to get it right the first time? measure. twice?

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Permalink Reply by Taffy Evans on April 8, 2019 at 7:51pm

Hi Daniel, what I would, and do, is before fitting the bridge permanently lay it on the top with the strings fitted to the guitar and tuned up. 

Your bridge will be in the " ball park" scale lengnth position. Set your intonation in the normal way with your desired action height and string gauge by moving the bridge and referencing a digital tuner. When you are happy mark the posi with tape. Fit the bridge when ready. If your strings terminate at the bridge take them to the tail using a mock up tailpiece.

i only use the two outside strings for this set up. I got photos if it helps.

Taff

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Permalink Reply by BrianQ. on April 9, 2019 at 1:28pm

Luthiers in a factory work off of jigs & templates, so the measuring has already been done for them, they just measure to confirm it’s within the correct parameters? Once you’ve done one, it’s all gravy from that point, taff is right on the money tho?

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Permalink Reply by Daniel Walter on April 8, 2019 at 7:56pm

thank you Taffy. makes sense.

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Permalink Reply by Daniel Walter on April 8, 2019 at 7:58pm

plus you can check the neck position with the two strings. bit of fiddling required, not for the less than focused mind.....................

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Permalink Reply by Taffy Evans on April 8, 2019 at 8:09pm

Nothing ventured nothing gained. 

Theres a saying I used to work by when I worked with people with disability years ago it was "try another way" I still keep that mind in my workshop now.

Taff

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