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Neck scale & bridge position question
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=42188		 Page 1 of 1
Author:  TAJ [ Sun Dec 15, 2013 1:52 am ]
Post subject:  Neck scale & bridge position question
This is a sanity check question, to make sure I'm adding things up correctly.

Project: I am replacing the bridge on this custom guitar. It originally had a LP Junior style stop bar as a wrap-around bridge. It didn't fit properly, and it wouldn't tune up properly. My buddy who owns the guitar asked me to replace it with a particular Gotoh wrap-around bridge (which is quite nice). So far so good.

A picture is worth a thousand words, but this forum doesn't allow image embedding by the looks of it (wtf?), so you get the 1000 words instead.

Problem: The Gotoh bridge isn't a drop-in replacement, it's saddles are offset from the mounting posts by 1/4" (the saddles are closer to the nut by 1/4"). Both the saddles and the post mounts on the new bridge are adjustable to a degree. I'm dowelling the old post holes and drilling new ones.

Scale: nut edge to crown of 12th fret is 12-5/16", double that is 24-5/8"

StewMac calculator (http://www.stewmac.com/freeinfo/Referen ... tcalc.html) says the bridge posts (therefore the saddles on a normal wrap-around bridge) should be located at 24.685" on the treble side (3/32" greater than scale).

So I add my 1/4" offset to this to get 7/16" greater than scale, or 24-3/4" from nut to bridge post on the treble side. And angle it slightly to to get an additional 3/32" at the bass side.

Does any of that sound horribly wrong?

Am I missing the method to include a picture here? I tried to "attach a file" but it would not accept a GIF file.) [headinwall]

..Todd
Author:  TAJ [ Sun Dec 15, 2013 2:40 am ]
Post subject:  Re: Neck scale & bridge position question
I see I can attach a JPG - fair enough. Here's the pic that should clarify things.

..Todd
Author:  dzsmith [ Sun Dec 15, 2013 9:16 am ]
Post subject:  Re: Neck scale & bridge position question
Todd,
I don't know the actual dimensions from the nut to the saddles, but I'd try to mount the bridge parallel to the nut rather than angled for appearance.
Author:  Freeman [ Sun Dec 15, 2013 11:48 am ]
Post subject:  Re: Neck scale & bridge position question
Todd, I have used the SM calculator to double check the location of the Gotoh bridge that I used on my Lester - it was very close to what was called for on the plans and intonated properly. One way you can double check is to put the old bridge back on temporarily and mark the location of each saddle. Then, since you said it "didn't tune up properly" (I assume that means it didn't intonate correctly) figure out which direction you would have needed to move the saddles and mark that (just guess, if it was sharp you would have needed to add a little compensation). Now temporarily position your new bridge and see if the saddles can be adjusted to the correct point. Compare that to your calculations and drill your posts.
Author:  TAJ [ Sun Dec 15, 2013 2:39 pm ]
Post subject:  Re: Neck scale & bridge position question
dzsmith,
The original bridge was angled and looked fine. dang, now you've got me thinking about it. No, it's fine. Visually, it's compatible with some headstock angles. 8-)

Freeman,
Good advice. I really should have investigated the intonation of the old bridge better, but the old post holes are dowelled in now, so that opportunity is gone. Yep, "didn't tune up" was a poor choice of words; severe intonation problems.

I'm not sure if there's a reasonable way to mount/test the position of the new bridge before committing. I think the effort involved to make up a temporary jig to hold it place without holes might be a serious challenge -- given the one-off nature of this project. A sanity check request was my alternative to that. I'm probably worried about nothing as there's close to a 1/2" of adjustment range between the post slot adjustments and the saddle adjustments.

I'm glad to hear of your confirmation in the StewMac calculator. My concern primarily lies with my own calculations and comprehension.

..Todd
Author:  TAJ [ Sun Dec 15, 2013 3:29 pm ]
Post subject:  Re: Neck scale & bridge position question
I should also mention that the original bridge was mounted such that the saddles were 24.5" from the nut (on the treble side). This is causing my apprehension. It seems to be a serious miscalculation on behalf of the original designer. I've measured the nut edge to 12 fret crown with every ruler I have and it consistently measures 12-5/16" which extrapolates to a 24-5/8" scale. Could I be missing something here?

..Todd
Author:  TAJ [ Sun Dec 15, 2013 4:40 pm ]
Post subject:  Re: Neck scale & bridge position question
TAJ wrote:
... the bridge posts (therefore the saddles on a normal wrap-around bridge) should be located at 24.685" on the treble side (3/32" greater than scale).

So I add my 1/4" offset to this to get 7/16" greater than scale, or 24-3/4" from nut to bridge post on the treble side. And angle it slightly to to get an additional 3/32" at the bass side.

Does any of that sound horribly wrong?


To answer my own question, yes, 24.685 + 0.25 = 24.935, not 24.75.

Note to self: Don't attempt simple arithmetic at 1:00 AM, esp. after drinking a bottle of wine (or more).

..Todd
Author:  Freeman [ Sun Dec 15, 2013 6:21 pm ]
Post subject:  Re: Neck scale & bridge position question
[quote="TAJ
To answer my own question, yes, 24.685 + 0.25 = 24.935, not 24.75.

Note to self: Don't attempt simple arithmetic at 1:00 AM, esp. after drinking a bottle of wine (or more).

..Todd[/quote]

Whatever you do, don't drill any holes......
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