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Another thread on bridge to center line placement got me to thinking. What kinds of tolerances do you build to, and where does it matter? Of course, the nut to saddle distance is critical, as well as the frets, but beyond that, what matters, and how much does it matter?

Now obviously, we are all trying to do the very best we can, but does it matter if the sides on your form are a quarter inch off from the plan at the lower bout? What about a half an inch? An inch? 2 inches?

So, what dimensions do you think are important and which ones have some flex to them?

For myself, I have not done enough of these things to have a valid opinion, but I try to match the outline to my plans pretty carefully. I also am a stickler about top bracing, more because my ignorance needs some guidance than anything else. Due to manufacturing errors, I have yet to be on target for body depth. My bridges are pretty close to center, but that's because I worry about how it would look if the strings were off center from the sound hole, not for acoustics.

I guess a follow up question is why are precise dimensions important, sound or looks?

Mike

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Mike Lindstrom

I've never used a plan so I can't answer about that. I try to keep the stuff that needs to be symetrical.....symetrical. That means the soundhole centered, compared to the waist, and the upper and lower bouts the same distance from center. On cutaways I keep the edge of the heel, and fingerboard perfectly flush with the body. If my goal is a body that 15 3/4" wide, or 4 7/8" deep I don't sweat a 1/16", or sometimes even an 1/8". Obviously, like you said, bridge location, fret slots ect need to be exact. The rest of the stuff, if it looks right,(and it will fit in the case) it's right.

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I didn't mean to say it, but I meant what I said.
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Fingerboard end to soundhole is an important one for me- it can get really awkward if you make a miscalculation with a design where the fingerboard end follows the soundhole radius (like most classicals). So I'd like to make sure that 19th or 20th fret is where it should be. (Not always successful in this!)
And I like to keep the 12th or 14th fret over the neck body joint pretty closely - within a 'few' millimeters.
I don't get too excited if a brace slips a bit out of place when gluing- again talking in terms of a couple or three millimeters here.

Looking at some of the interior shots of guitars by past masters (e.g. Torres) shows nice, clean work- but not obsessive. You gotta keep this all in perspective!

Cheers
John

I have a friend who built his second acoustic and the entire treble bouts were larger than the bass bouts...really larger, noticable from ten feet away. I had to ask, "Did you do that on purpose? It looks kind of odd." He replied, "Who's to say it's wrong afterall I am the creator, builder." He laughed and said it makes the treble notes sweeter. "Yea that's it an increase in chamber volume on the treble side." It later became firewood.

He did make a good point saying he was the creator and who's to say it was wrong.

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"Try to be the person your dog thinks you are."

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Most don't really matter much for a Guitar to function as an instrument...

In my mind, everything related to the musical scale is a "Critical Dimension" ... The instrument won't ever play right if the frets are in the wrong place or the nut/saddle is in the wrong place...

Fretwork and setup also qualify in my book....

Getting the strings lined up on the fretboard right also seems to be fairly important....

The "Neck feel" also seems pretty important, though it is very subjective...

Everything else isn't so much so.... Sure, it may look a little Hinky if the body is lumpy... or if you can't buy a case for it... but it can still fulfill a Primary purpose as a musical instrument....

The converse of this is a project guitar I saw in a pawn shop.... Someone obviously spent a whole lot of time and money on it... Spectacular wood -- Master grade Rosewood and Spruce (Looked like Adi), very tight joints, fit in the case beautifully, spectacular finish.... Everything *looked* just right... until I tried to play it.... Fretwork was a total mess -- the fretboard wasn't cut right, the bridge wasn't in the right place, etc... It wouldn't play *Anything* in tune..... I understood perfectly ..... This is why it is in this pawn shop...

Thanks

John

I just had a few words on this in the other thread.

Basically, as has been said, the fret distances are the most critical: the tolerance there is set by mathematics and the ability of people to hear differences. After that, it all depends on who is setting the tolerances, and why.

Most American guitar buyers are so used to seeing and playing mass produced instruments that the only sort of tolerances they know about are production ones. Essentially, any measurable or visible deviation from 'perfect' is simply not tolerable, no matter how much or how little it effects the function. The guy who built the pawnshop box that truckjohn saw got that one backwards: he seems to have gotten all of the tolerances right _except_ the important ones.

The other end of the spectrum, in my mind, is the 'functional' standard, where anything goes so long as it works right. Most of us, I'm sure, want to put some sort of esthetic standard in there too, and that leads to what, IMO, is the 'proper' standard for us, the 'craft' one.

Of course, there are all sorts of levels of the 'craft' standard, and where you come in on that will depend on your level of skill and esthetic sense. Strad is sort of the epitome of that standard: he just made the cut and it was 'right', even if it was not the same as the cut on the other side. But his work is also beautiful, in part precisely _because_ it is not 'perfect'. Modern violin makers strive endlessly, and mostly without success, to achieve the combination of precision and 'flow' that Strad did week after week gfor decades. Those decades are probably the 'secret' too, along with a long tradition. We see that also in much Japanese craft.

For us, since the folks we're trying to sell to are already indoctrinated to the stricter 'production' standard, we're sort of stuck trying to approach that. We can't get away with even the level of 'craft' that Strad showed: sanded surfaces are manditory, and tool marks are out. And heaven forfend that one shoulder of your axe would end up higher than the other, the way Strad's 'G' mold did!

I use the finish carpenter's adage...Fir it in, let it run wild, and cover it up with trim.

I thought of another one that matters, the distance between the tip of the heel carving chisel and the shoulders of the guitar seems to be important. I have yet to leave a large enough gap. I think I'm going to try shaping the neck completely off the body next time.

Mike

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Mike Lindstrom

I've finished 5 guitars to date, so take my perspective in that context.

I've tried to do most of my work from scratch, for a couple of reasons. One is that I get a greater level of satisfaction from the finished product when I know that I laminated the neck from rough stock, thicknessed (and on occasion, resawed) my back and sides, bent them (on a pipe) and built my own molds and jigs from scratch. I've found my own point in the continuum of "do it yourself", where I'm comfortable. While I don't cut my own inlay, I do make my own saddles and nuts, from cowbone, purchased at the A&P.

As a result of the "do it yourself" elements of this, no one would ever mistake my guitars for production guitars. I strive to eliminate the imperfections, and make them more repeatable, and I'm succeeeding, slowly, from one to the next, but if extremely fine tolerances on all points of assembly were the number one objective, I wouldn't do it this way. For me, the process of recovering from errors is part of the fun, and a big part of the learning.

Big preamble: For my building, what I've learned the hard way in terms of the "measurements that matter" are as follows, in priority order.

"Function" of the guitar.
Neck angle, and neck joint fit.
Fretboard flatness (ok, and relief when strung), geometry of frets, dressing of frets on ends (hate that sharp feeling on the left hand) nut and saddle setup, height, etc.
While I can't provie it, I suspect that fit and joinery of sides to top and back, and fit and gluing of braces are extremely important to sound.
"Feel" of neck - e.g. what is the profile, thickness of neck.
Geometry of the strings along the neck, from the nut to the saddle (too close to the edge - no good, etc.)
Width of the nut and spacing of the strings on the nut (Stewmac's tool works for me).
Thickness of the top - mass, stiffness, placing, carving of braces.

I'm sure I'm missing things.....

"Cosmetics" -
Maybe not critical to function, but sure does look crappy when you don't get it right.
Precision of binding channels - depth - tightness of binding and purfling when glued (yeah, I know there's a very important function for bindings, but what I'm saying is you could have it be structurally sound and still have visible gaps that just look shoddy).
Symmetry of the sides (e.g. - how perfectly does the side bending meet the perfect mold. I think this matters very little for function, but can be very visible. The one caveat is that asymmetry creates angles and other challenges that must be compensated for in later assembly, neck joint, etc.

Lots of others - don't think this was the intent.

Interesting discussion.

I think Al makes a great point about the difference between the Hobby builder (ME) and the Pro Luthier (Him)

The Pro builder can't get any respect unless your work looks at least as good as a Factory instrument... And -- the assumption is that the basic problems around the musical scale, fretwork and associated playability have already been worked out.... I would be pretty disappointed if an actual Professional Luthier couldn't get intonation and fretwork at least as good as an $800.00 factory guitar... That is cost of entry sort of stuff...

It may actually be worse for a Pro Builder dimensionally - Look at an actual 1930's Gibson or Martin... Dimensions were all over the place.... They could easily be 1/4" - 1/2" different in outside dimensions guitar to guitar.. and quite Asymmetrical... but yet the Pro builder is expected to hold far more precise tolerances on reproductions of these instruments than the original makers ever did...

As a Hobby Builder -- especially a new one... My personal opinion is that the 1st goal should be to figure out how to make an instrument that works right as an instrument... We aren't building Coffee tables or Kitchen cabinets... It is supposed to make Music... The things that help are getting a good fretboard, getting the nut and bridge in the right place, and then taking the time to try to understand how setup works and get it right....

Then.. Once the Hobbyist works out that stuff -- Using precisely cut fretboards, doing good fretwork, gluing bridges into the right place, Making and adjusting the nut and saddle for the proper action and intonation.... We should move on with trying to get the instrument feeling better, more pretty, more responsive, and sounding better... Doing it the other way around -- Making it pretty 1st, then slowly working your way into getting Intonation and Fretwork right ends up making a big pile of expensive guitar shaped duck houses and end tables while on the way to "Musical Instrument"

Thanks

John