string height at bridge.

Construction and repair of Classical Guitar and related instruments
Stephen Eden
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Location: Bexhill on Sea, England

Re: string height at bridge.

Post by Stephen Eden » Fri Mar 18, 2016 10:06 am

One thing to note Chris is that although the neck rises, the top will also drop slightly too as the strings pull the bridge forward. I would think if the neck pulls forward far enough that you have to adjust the saddle by 1mm or more you should probably re-fret instead as it will probably start to get awkward playing in the middle of the neck.

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Chris Sobel
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Re: string height at bridge.

Post by Chris Sobel » Fri Mar 18, 2016 4:17 pm

Stephen Eden wrote:One thing to note Chris is that although the neck rises, the top will also drop slightly too as the strings pull the bridge forward. I would think if the neck pulls forward far enough that you have to adjust the saddle by 1mm or more you should probably re-fret instead as it will probably start to get awkward playing in the middle of the neck.
Stephen,

I would agree -- I was making an extreme case up to illustrate a point. I usually have to adjust the saddle + or - .5 mm or less, but usually a tad to get things dialed in.

Thanks,

Chris
CE Sobel Guitars

Massimo Barbi
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Location: Connecticut, USA

Re: string height at bridge.

Post by Massimo Barbi » Sun Jul 16, 2017 1:02 am

A question about bridge height in relation to string height at the bridge- I'm reading here that common string heights at bridge are 10.5 - 11.5mm, even 9mm or lower. My problem is that the books I've used to build my first two guitars (Cumpiano/Natelson & Courtnall) have bridge height dimensions that were 10mm. This leaves only .5 - 1.5mm for saddle projection, or even less than 0. What height bridges do makers who use those lower string heights use? If I can safely reduce my bridge height and thus saddle height, I could resolve the high action problem I've been plagued with.

This would be especially helpful on my last instrument, where the neck angle and top dome came out exactly right and a straight-edge on the frets reads 4.5 - 5mm high at the bridge, and still mysteriously has 4mm high action on the high 'e' with the saddle projecting only 1mm.

Thanks!

Imbler
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Re: string height at bridge.

Post by Imbler » Mon Jul 17, 2017 11:01 pm

Massimo, something doesn't seem to add up.

You have 4.5 minimum height at bridge with straight edge on top of frets. So your 4mm action at high e would give a string height of 4.5 plus two times 4mm action equals 12.5. So you should have 2.5 mm of saddle showing over your 10 mm bridge.

I would suspect something was mis measured or you have a very flexible neck that is pulling up under tension to increase your action. The latter would be pretty rare for the low tension of a classical unless you have a very thin neck,
Mike

I just edited this to note that neck pull up is discussed previous to my post and they give some typical numbers of .5 mm or less of saddle adjustment.

Massimo Barbi
Amateur luthier
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Joined: Mon Feb 29, 2016 1:37 am
Location: Connecticut, USA

Re: string height at bridge.

Post by Massimo Barbi » Tue Jul 25, 2017 12:41 am

You are correct. I'm not sure what math I was doing there. I did have a back bow from being in a humid location for a while, and I must have measured the projection on the forward slope of the bow, giving me a falsely low measurement. In either case, I reduced the height of the bridge and the saddle slot too, and was able to get the action at 2.8 or so on the high e, so that worked. And the neck straightened out again. I missed that the Romanillos plan I was using had a lower bridge height, unlike the 'build' section of the book, by Courtnall.

Thanks for pointing that out.

Imbler
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Re: string height at bridge.

Post by Imbler » Tue Jul 25, 2017 12:44 am

Glad it had a happy ending!
Mike

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