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| Split through bridge pin holes http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=8669 |
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| Author: | JJ Donohue [ Sat Sep 30, 2006 7:21 am ] |
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Terry...I don't know why this happened but on future bridges you might want to consider drilling the bridge pin holes with their center lines parallel to the saddle slot. That way there isn't as much stress on a single grain line. |
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| Author: | GregG [ Sat Sep 30, 2006 9:15 am ] |
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I know some will drill their pin holes in an arc or slant to avoid a grain line split like this. Greg |
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| Author: | Serge Poirier [ Sat Sep 30, 2006 9:19 am ] |
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Great tip there JJ! Terry, you could also do a pattern like mine and put the low and high G strings at the same distance from the front of the bridge and move the inner strings backwards (1 mm) by pair of strings ie 5th paired with second and 4th paired with the 3rd string, if i make any sense. The result should be a smile as Greg said!  |
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| Author: | David R White [ Sat Sep 30, 2006 9:54 am ] |
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I have also moved to flitch cut for the bridge to lessen the chances of splitting. |
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| Author: | Alan Carruth [ Sat Sep 30, 2006 10:44 am ] |
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Sometimes I've seen this happen when the bridge pins were tight. They're toggles, and don't really need to be seated tightly to do their job. Six of those on one grain line can easily wedge a brittle wood like ebony apart. That, and the weight of the stuff, have pretty well turned me off from using ebony for bridges. |
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| Author: | crazymanmichael [ Sat Sep 30, 2006 11:00 am ] |
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regardless of the wood used, i try to have the grain going one way on the long diagonal and the axis of the pin holes the other. i also prefer to have the stock cut off quarter + or - 40 degrees. it all helps to prevent crating lines of weakness along the grain. |
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| Author: | Kelby [ Sat Sep 30, 2006 2:01 pm ] |
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This does not look like a crack along a single grain line. The crack between the D and the G strings look higher than the rest. If the crack is not along a single grain line, then my guess is that the bridge dried out after delivery and tried to shrink, but that the bridge pins/string/top prevented it from shrinking, so it cracked. |
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| Author: | Frank Ford [ Sat Sep 30, 2006 2:13 pm ] |
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In my not particularly humble opinion, this risk of this kind of crack can be reduced significantly by orienting the grain of the bridge plate parallel to the top grain. That way, the here's much less tendency of the top and bridge to try to bend upward as a result of string tension. Particularly when heat is present and aliphatic resin glue turns to chewing gum, I think there's a good tendency to acquire such bridge cracks as the bridge gets stress right in the middle. Whenever I try to repair one of these with CA, I always add a bridge plate overlay with the grain parallel to the top grain. After all that's the direction of all the string tension, and the ONLY top failure that happens in this area. So, am I saying that guitar designers are wrong when they orient the grain of the bridge plate parallel to the bridge grain? Yup - that's the way I see it - plain and simple. In the same conversation, good ol' Mike Longworth told me that Martin leaves the bridge pins standing a bit "proud" because some players like to tap them in tightly, and later that bridge cracks were due to players hammering the pins in too hard. Personally, I just don't buy that anymore than I do the "shrinkage" issue. Makes too little sense compared to all that string tension pulling straight up under the bridge. . . |
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| Author: | CarltonM [ Sat Sep 30, 2006 2:52 pm ] |
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Frank, that just sounds too reasonable. You must not know what you're talking about. 
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| Author: | Kim [ Sun Oct 01, 2006 12:04 am ] |
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Yeah, I'm with Carlton Frank, that grain orientation theory of yours sounds ridiculously sensible to me. It could not possibly be correct.
Seriously though Frank, have you put this into practise? Now that you have pointed it out, it really does sound sooo obviouse...but then, that why your Frank of Frets.com and I'm Kim of little lutherical achievements 
Cheers Kim |
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| Author: | Terry Stowell [ Sun Oct 01, 2006 11:23 pm ] |
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I woulda thought anything off square or parallel woud be best. (45 degree or so) Aligning adjacent grain doesn't make sense to me.... But then again... I may need a little convincing  I need to see some graphics. LOL!
I'm leaning toward staying away from ebony bridges too. Love it's look, but they are heavier than Brazilian
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