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| Bridge location to centerline tolerance http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=27362 |
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| Author: | pjsch [ Wed May 12, 2010 12:30 pm ] |
| Post subject: | Bridge location to centerline tolerance |
How close to centerline of the top is a reasonable tolerance to shoot for when aligning the neck to the top? I have my neck joint to body almost perfect, no gaps, good neck angle, but the centerline projection to bridge location is off center about .030 to .040. How far off center is too much? This is my #4. My #1,#2, and #3 I spent as many hours as it took to get it within .010. Closer the better , but when to call it good enough? After getting the neck this close with a good joint, I don't want to end up chasing the neck angle, centerline, and joint fit again just to get a perfect alignment. Pat |
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| Author: | Mike Collins [ Wed May 12, 2010 12:48 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
your talking 1mm MAX! This is acceptable -wood swells & and poop happens! No one but you will ever notice. I've seen bridges as far as 4mm off center-because I do alot of repair work Plus tone will not suffer. BUT I shoot fo NO tolerance-check out your jigs or method of fitting to make sure you get it spot on in the rest of your guitars. You'll be much happier if you figure what is causing the misalignment . good luck! Mike 
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| Author: | WaddyThomson [ Wed May 12, 2010 12:53 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Not a SS, but I've read that Hauser positioned his bridges off center on purpose, to the treble side, as much as 1/8". |
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| Author: | Alan Carruth [ Wed May 12, 2010 2:19 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Mike Collins wrote: "No one but you will ever notice." Don't be too sure. There was a thread last year on one of the groups started by a fellow who had noticed that his bridge was 1/16" closer to one edge than the other. That's 1/32" off center, considerably less than a mm. He was worried that this might not be 'acceptible'. Most of the builders on the list asked the usual practical questions, like whether it sounded and played OK. A couple of the players insisted that this was simply too far off, and that he should return the guitar for an immediate refund. It became quite a long thread. There are obviously people in this world who simply have no idea about what's important, but who are more than willing to impose their witless standards. |
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| Author: | Fred Tellier [ Wed May 12, 2010 2:59 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
At 10 or so paces away it can be of quite a bit and no one will notice, except the guy Al mentioned who it sounds like checked his guitar with a micrometer. I also spend way to much time worrying about getting this perfect as I will always know if its out. Fred |
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| Author: | Tom West [ Wed May 12, 2010 3:13 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
This could turn into a real interesting thread,not just about how close the bridge should be to being on center but in regard to tolerances in general. What are they ,and who establishes them,the builder, the customer, the luthier community. Think it's a complex proble we all have to struggle with and there is no easy answer. Tom |
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| Author: | wbergman [ Wed May 12, 2010 3:23 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
My 1980 Kohno 30 has the bridge glued off center. I did not notice when I bought it, or I would not have. It's enough difference that I had more than the usual problem pulling the high E off the finger board at times. A few years ago, I had the holes plugged and the bridge redrilled to get the strings aligned properly. Off course, now the error is more visible, but at least I play a little better. |
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| Author: | Colin North [ Wed May 12, 2010 3:40 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
wbergman wrote: My 1980 Kohno 30 has the bridge glued off center. I did not notice when I bought it, or I would not have. It's enough difference that I had more than the usual problem pulling the high E off the finger board at times. A few years ago, I had the holes plugged and the bridge redrilled to get the strings aligned properly. Off course, now the error is more visible, but at least I play a little better. 1/16th off in bridge centring is one thing, in string positioning it can be a bit more inconvenient. Depends on when you drill the pin holes. |
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| Author: | JohnAbercrombie [ Wed May 12, 2010 3:54 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
wbergman wrote: My 1980 Kohno 30 has the bridge glued off center. I did not notice when I bought it, or I would not have. It's enough difference that I had more than the usual problem pulling the high E off the finger board at times. A few years ago, I had the holes plugged and the bridge redrilled to get the strings aligned properly. Off course, now the error is more visible, but at least I play a little better. It sounds like the neck was properly aligned but the bridge glued in the wrong place- very irritating! This points out the fact that it is the alignment of the bridge (and the string holes/spacing) with the neck that is the critical thing. Nobody will notice if the bridge is a bit off-center, but if the bridge/strings aren't lined up correctly with the fingerboard, it will be very obvious, especially to the player. A spool of thread (better than string) to check alignment and double- and triple-checking before gluing the bridge are good ideas. A notched saddle can be a temporary work-around if you have a guitar with string alignment problems. Cheers John |
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| Author: | Tom West [ Wed May 12, 2010 4:32 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Pat: Think you had answered your own question before you even asked it here on the forum. Your tolerances were established in your first three guitars. Deep in your heart you will feel like your taking a step backwards if you use a different dimension.Now a days when I see some of my earliest guitars I have second thoughts about some of the things I let slip by,wittingly or unwittingly.Good luck with your decision. Tom |
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| Author: | JohnAbercrombie [ Wed May 12, 2010 4:43 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
pjsch wrote: How close to centerline of the top is a reasonable tolerance to shoot for when aligning the neck to the top? I have my neck joint to body almost perfect, no gaps, good neck angle, but the centerline projection to bridge location is off center about .030 to .040. How far off center is too much? This is my #4. My #1,#2, and #3 I spent as many hours as it took to get it within .010. Closer the better , but when to call it good enough? After getting the neck this close with a good joint, I don't want to end up chasing the neck angle, centerline, and joint fit again just to get a perfect alignment. Pat Pat- How have you determined the centerline? Is this the center joint line of the soundboard, or the mid-distance point across the lower bout, or...? You are talking about 1mm or less, right? ![[uncle]](./images/smilies/surrenderflagqv6.gif "Uncle") Cheers John |
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| Author: | pjsch [ Wed May 12, 2010 5:19 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
I use the soundboard centerline joint. The centerline to sides dimension can vary 1/8 inch or more side to side. I ignore this variation as it is hard to control and overall body dimension variance shouldnt have an effect on tone or playability. I was curious what others shoot for in setting this alignment. Placement of the bridge in relation to the bridgeplate and X braces is what would be affected and I don't see how .03-.04 would make a difference there. One end of the bridge extending farther over its X brace than the other side could be a problem but it would have to be a lot more that .03-.04 to be a problem. But as others have pointed out, if it can be made dead on center why not do it. I will probably work on it to bring it closer to center. Pat |
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| Author: | es guitars [ Wed May 12, 2010 5:55 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
I am just starting my first harp guitar build. I have the GAL Dyer plan and if you put a straight edge down the center line of the top the you will see that the neck has quite a bit of a tilt to the right. I assume to get more clearence between the bass arm. the top is X braced with the X crossing in the center of the top. If you look at the bridge it is way way off center with the bass wing only a couple inches from the edge. I plan on changing the design on my build to get the bridge more in the center. This means my neck center line will be about 1 5/16 " off the center line of the top. And my bridge still will not be in the dead center. So I also wonder what effect this will have. Brent |
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| Author: | JohnAbercrombie [ Wed May 12, 2010 7:03 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
pjsch wrote: ................................ but it would have to be a lot more that .03-.04 to be a problem. But as others have pointed out, if it can be made dead on center why not do it. For me, within a mm or two on this sort of thing isn't a problem (I do try to get the string to fingerboard edge spacing good to about .5 mm, though.) Why not do 'better'? At some point I feel it is the time to 'push on' and get the project completed. Trying to get everything 'perfect' is just not feasible, or very productive. It's part of the whole 'craftsman/artisan' approach, for me. Then again, I've read of some folks boasting they work to within .001" with wood, so lots of different opinions on this! Cheers John |
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| Author: | jfmckenna [ Wed May 12, 2010 7:22 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
I actually have an insane ability to notice when things are off ever so slightly. BUt even I wouldn't worry about a 1mm difference. Well... ok I'd worry about it but I at least know no one else would. ![[:Y:]](./images/smilies/smiley20.gif "Thumbs Up")
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| Author: | walnut47 [ Wed May 12, 2010 9:07 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
WaddyThomson wrote: Not a SS, but I've read that Hauser positioned his bridges off center on purpose, to the treble side, as much as 1/8". Waddy, I think Hermann was onto something. Asymmetry is a good thing. Walter |
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| Author: | Foster [ Wed May 12, 2010 9:17 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
I'm getting a visual of "Monk" scrutinizing a guitar holding his thumbs at arms length saying, "Somethings just not right." |
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| Author: | JohnAbercrombie [ Wed May 12, 2010 9:26 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Foster wrote: I'm getting a visual of "Monk" scrutinizing a guitar holding his thumbs at arms length saying, "Somethings just not right." I think the 'Obsessive-Compulsive Registration' lineup would be long at most luthier get-togethers! 
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| Author: | mhammond [ Wed May 12, 2010 11:14 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Mr. Somogyi says that mounting the bridge so there is a little extra room on the treble edge of the fretboard is a good thing. I did this to the last one and am waiting to hear back from the new owner as to the results. Mikey |
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| Author: | Daniel Minard [ Thu May 13, 2010 12:26 am ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Alan... You crack me up! Thanks for a good laugh. |
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| Author: | Colin S [ Thu May 13, 2010 4:33 am ] |
| Post subject: | Re: Bridge location to centerline tolerance |
If it is less than 1mm off centre, just a few sandpaper flossing strokes on the heel will bring it on centre, why not do it right if it is so easy? Colin |
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| Author: | Michael.N. [ Thu May 13, 2010 4:48 am ] |
| Post subject: | Re: Bridge location to centerline tolerance |
1 mm off wouldn't overly concern me. That's just my opinion and I guess there does come a point where it becomes unacceptable. Ultimately you make your own decisions on these type of parameters. For some makers perhaps 0.2 mm is too far off. . . |
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| Author: | John Ray [ Thu May 13, 2010 7:46 am ] |
| Post subject: | Re: Bridge location to centerline tolerance |
I glue the bridge on using a plywood mock-up of the string layout. I move the bridge over to the bass side in order to get that "little extra room" on the treble edge (doesn't everybody?) and so I suppose my bridge is off centre. However in 140 guitars I have never checked it. Where does it say that the position of the bridge is in the centre anyway? John Ray Granada |
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| Author: | Bill Hodge [ Thu May 13, 2010 9:37 am ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Greg German in Broomfield CO makes a pretty good case on behalf of asymmetry. 
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| Author: | Alan Carruth [ Thu May 13, 2010 12:33 pm ] |
| Post subject: | Re: Bridge location to centerline tolerance |
Tom wrote: "This could turn into a real interesting thread,not just about how close the bridge should be to being on center but in regard to tolerances in general. What are they ,and who establishes them,the builder, the customer, the luthier community. Think it's a complex proble we all have to struggle with and there is no easy answer. " That's where the other thread went. To me it all comes down to 'what matters?'. You'll get different answers from different people, of course, depending on the circumstances, so there's no one 'right' one, but there are standards. Sadly, an awful lot of these standards seem to default to the 'production' level, which is where that guy was coming from, probably without knowing or thinking about it. In a mass production setting the object is to make identical interchagable parts. Any deviation from 'perfect' jeopordizes that. I remember Bob Taylor talking about the time they put an extra coat of finish on some necks, and had to throw them out because they no longer fit the neck pockets. Correcting such an out-of-tolerance issue takes a lot of time, and time is the most expensive intput in mass production. So, for Taylor, getting the bridge a millimeter off center is as bad as getting it a millimeter off in the length direction. For us, the latter is far more problematic than the former. Getting the length wrong messes up the intonation, but getting the bridge a little off center just makes problems with the string alignment on the fingerboard. Maybe: maybe you needed to move the bridge because the neck is off center! The poster in the other thread defined the 'center' as the line halfway between the wide points of the bouts. Again, in a production setting, that had probably better be where the center join is. For us, often enough, there are some little asymmetries in the shape, and the center join is a far more visible and meaningful 'center' to shoot for. But, of course, that's not always the case in hand making either: Romanillos mentions that Torres' tops seldom had the center joint on the center line, in part because they were often not book matched. Which makes the point that, in a craft setting, there are often very good reasons why things would not be 'production perfect'. Torres used trhe best wood he could get, book matched or not. Obviously we strive for tight fits and perfect surfaces, but the fact is that there's no way to get the best possible sound and playability consistently unless you can vary things a little. Any time you do that it puts a premium on tool chops: you can't rely on the jig to get it right. Is there anyone among us who doesn't sometimes wish he had better tool chops? So the reality is that in a craft like ours there will be times when stuff is just 'off' a little. IMO, if it's little enough so that it doesn't hurt the function of the instrument, and it doesn't look bad, then it's not a 'defect', as it would be in a production setting. That, to me, is a proper 'craft' standard. Now if we can only get the customers to accept that! |
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