Newbie guitar repair questions - Yamaha acoustic

[vintshave]

Originally Posted by charles Tauber

I did explicitly say, "There is some technique involved to produce a flat surface without tearing the #$^% out of the softwood top." Now you know, first-hand, what I meant. Ditto for a scraper. That was contained in my statement, "If you don't have or are unfamiliar with a cabinet scraper, I suggest...learning to sharpen and use it." What you have experienced is the first step in "learning to sharpen and use it". You now know how not to use it in this application. A scraper will exaggerate hills and valleys if used parallel to the hills and valleys. Used perpendicular to the hills and valleys it will lop off their tops producing a flat surface. For a gluey mess, start by removing some of the excess using the chisel as a chisel.

Charles, if I keep the scraper perpendicular (vertical) to the guitar top, I would only be guaranteed flatness of the overall surface if I could keep the scraper at an identical vertical height throughout the scraping process (like setting up a router). How would I do that part?

Originally Posted by charles Tauber

I use the screws, as I described. Simple, dead-accurate, no shifting during gluing.

I was thinking more in terms of how do you ensure that a bridge is in the correct place on the guitar. This may be a more academic question. I was just curious

[charles Tauber]

Originally Posted by vintshave

Charles, if I keep the scraper perpendicular (vertical) to the guitar top, I would only be guaranteed flatness of the overall surface if I could keep the scraper at an identical vertical height throughout the scraping process (like setting up a router). How would I do that part?

A scraper/chisel isn't a router. A router is set/held at a certain depth and anything in it's way is removed, without regard to what is in its way.

Neither a chisel or a scraper is used that way, generally. Instead they are used in conjunction with/response to what "is in their way". One alters what one does with the tool to suit what needs to be done/removed. That's where technique and skill fits into it. For example, one identifies high spots then selectively works on the high spots to reduce their height, rather than treating the surface uniformly. It's about identifying what needs to done and then doing only and exactly that. Just running a scraper back and forth, for example, and treating the surface uniformly doesn't guarantee success. Instead, first identify what condition you have, then work selectively towards what you want to end up with. In some circumstances, this is an identifying difference between power tools and hand tools.

Think of a bulldozer and a large hill. If the goal is to remove the hill, making it level with the surrounding land, you wont just drive up to the side of the hill with a bulldozer and start pushing. That's, more or less, what a router does. Instead, the bulldozer will start by selectively removing material from the top of the hill, starting, perhaps, where it is highest and gradually change what area to work on as the entire hill is slowly lowered. The results of one action are accessed to determine what will be the next action. It's a closed feedback loop in which the previous action determines what the next action should be, iteratively until the desired result is achieved. Different from just pushing on the side of the hill with the bulldozer (router).

While I haven't tried it, I'd bet that with a good router, capable of height adjustment to a thousandth of an inch or so, you probably could level the glue/mess where the bridge was. But, recognize that it is a different approach. No, I wouldn't even dream of trying that with a Dremel.

I was thinking more in terms of how do you ensure that a bridge is in the correct place on the guitar. This may be a more academic question. I was just curious

Sorry, I misunderstood your question.

Short answer: know the scale length, add compensation, design a bridge around that to locate the saddle, slot and the bridge pins and allow sufficient material all around for structural integrity. Ultimately, the position of the bridge is all about putting the saddle where it needs to be to achieve the correct (compensated) string length.

For an existing guitar, you don't have that much choice about where the bridge goes since the finish and pin holes pretty much establish where it's gotta go. You can determine if the string length is correct by measuring from the nut and adding 3 to 5 mm to the scale length. That'll give you a ball-park measurement. If the guitar still has its bridge attached, just check the intonation. If the intonation is acceptable, the bridge is in the right location - actually, the saddle is in the right location. if the intonation isn't correct, it'll be a lot less work to move the saddle slot than to reposition the entire bridge. See other recent discussions on filling and recutting the saddle slot.

[vintshave]

Again, thank you for the comprehensive explanation and the bulldozer metaphor. So there IS a lot of "art" to this craft. Apparently not everything can be accomplished with a stewmac jig . After seeing all of their stuff, one wonders how guitars were made in the old days ;-)

[charles Tauber]

Originally Posted by vintshave

So there IS a lot of "art" to this craft.

At the risk of nitpicking, I'd say no, there isn't. There is, however, a lot of craft to this craft. Many people have lost the meaning of "craft" and what it meant to say that someone was a craftsmen/craftsperson. It meant that one was well versed - had knowledge and skill - in the tools they used - originally hand tools - to produce a high quality result with those tools. And, obtaining that knowledge and skill took a lot of time and effort. The basic skills are technology, rather than art.

I think that it is great that many people these days want to make and repair their own guitars. But relatively few doing so have the basic tool skills and knowledge necessary to do so well. Some learn those skills along the way - that's how I did it. Still, I find I often just shake my head when I read about peoples exploits without knowing how to properly sharpen a chisel or use a plane. I'm happy to help those that want to develop those skills, even as I continue to develop my own skills.

Things get more interesting when one begins to mix in power tools, manual machines and, more recently, CNC machinery.

With the internet, Youtube, discussion forums... there is so much more information available now than even 10 years ago. But that doesn't replace "craftsmanship" and the knowledge and skill required to achieve that.

Soap box off.

Apparently not everything can be accomplished with a stewmac jig .

The catch is, it probably can. Or you can learn to use a small number of simple hand tools well to do what their catalogue of tools does.

Here is an example. In less time than it takes to change the collet and bit on your router, you can make perfect hand-cut dovetail joints used in furniture construction. But, it may take several years of daily dovetail making to achieve that. Here's an example of "craftsmanship" from one on my teachers, Rob Cosman, doing "The Three Minute Dovetail Joint":

http://www.youtube.com/watch?v=xxIgNel0H_I

Don't misunderstand me: in the right context there are lots of advantages to power tools and jigs and fixtures.

After seeing all of their stuff, one wonders how guitars were made in the old days ;-)

By using a few, simple hand tools well.

Technology allows more to be made in less time for less money. Often with greater consistency.

While I love using hand tools, I power thickness sand backs, side, fingerboard, etc. In the old days, I hand planed all of that. It is so much quicker and easier to power sand them. I still hand-plane all tops. I like having the ability to choose.

[vintshave]

My far greater expertise is in the world of blades and their care. I have one of the world's largest collections of (primarily) straight razors - I think I'm up to 1,300 at last count. I understand and have a great respect for craftsmen - both the people who made something which, even in the 17th century, was fine enough to bisect a hair cleanly and those of us who have spent tens of thousands of strokes learning to hone the product of their labor.

I believe that learning to work the hand tools before going to power tools and jigs, is essential. It keeps you more "in touch" with the work and both the consequences of doing something right and doing something wrong. Power tools in inexperienced hands enable them to do "wrong" a whole lot faster and worse than had hand tools been employed. Sometimes I think that the Dremel has destroyed as many projects as it has aided.

A primary driver of the loss of crafts such as woodworking, metalworking, etc. is our tolerance for cheap, poor quality products, as well an an economy that does not reward such work. Personally, it is a colossal waste of my time financially to ever touch a tool - hand or power. Buying is almost always cheaper than building. But there is something about the feel of the tools in your hand, the smell of the workshop and the look of the workbench located on one side of my 2nd floor office, that is immensely comforting, pleasurable and satisfying. And creating something that you can put to use - something with which you can make music - is awesome indeed.

I appreciate that you have taken the time and effort to pass along the craft to me. I hope that my questions are not too tedious.

[charles Tauber]

Originally Posted by vintshave

I have one of the world's largest collections of (primarily) straight razors - I think I'm up to 1,300 at last count.

Impressive, indeed.

I understand and have a great respect for craftsmen

Sounds like we're on the same page.

I hope that my questions are not too tedious.

No, not at all. They are well thought-out and well expressed.