Preparing the Back and Side Plates
There are a number of steps between buying a piece of lumber, and turning that wood into a guitar.
The sapele that I bought was quarter-sawn, which means that it was purposefully cut in the sawmill with the grain running completely vertical. As opposed to traditional lumber preparation, in which the log is rift sawn to produce the maximum number of boards, quartersawing does involve some careful planning, and more time to produce the lumber. The resulting pieces, however, are much more stable and less prone to warping and twisting than rift-sawn wood.
While it is possible to build a guitar with rift-sawn wood, I try to use quartersawn plates whenever I can. The resulting instrument will be more likely to last way beyond my lifetime.
Far and away, the best tool purchase I've made over the last several years has been my Jet 14-inch bandsaw. With a 12-inch riser block attached, I can resaw just about any board out there.
Resawing is the process - as you can see in this picture - of taking one relatively thick (about 13/16 inch) board, and sawing it into sections, or plates, each a little thinner than a quarter inch.
I use a Woodcraft Timberwolf blade, which tends to make things much easier.
In this picture, I am resawing one of the future sides to my guitar. After that, I will also produce two plates that will be joined to become the back of the guitar.
By the way, it's hard to see the writing on my tee shirt in many of these pictures, but it says I WRITE DEAD PEOPLE on the front, and has pictures of my books on the back.
I am not above becoming a walking billboard for my published works!
When it is properly thinned, a guitar side can often be flexed quite easily. Getting it to bend and hold a shape, however, takes some work, which I'll detail in a future page.
To begin the thinning process, I use my Delta portable planer. This is a very dangerous tool, and you can be certain that I'm extremely careful with it. Inside is a drum with two incredibly sharp knife blades rotating at something like 10,000 rpm.
I can adjust the height using a crank on top of the machine. I take off about a tenth of an inch with each pass, until I'm within two or three tenths of my desired thickness. The thinner you get your piece, however, the more careful you have to be. I've played the odds too closely on more than one occasion, and this little baby has turned my resawn piece into toothpicks and splinters.
There are other ways to thin your stock, of course. The most popular way is to use a hand plane with a toothed blade, planing in first one direction and then another, then change to a smoothing blade to erase the tooth marks, and finally finish the job with hand scrapers. This is the traditional method, and is detailed very nicely in Cumpiano and Natelson's book Guitarmaking: Tradition and Technology.
I've done it both ways, and I really prefer using the power planer. It's faster, and the resulting piece has a much more uniform thickness. Stradivari would frown, of course, if he weren't dead, but I bet he'd have used one of these babies if they'd been around in the seventeenth century!
I've thinned them about as much as I dare with the planer.
When you resaw thick boards like I've done, and then lay the resawn pieces side by side, you get pieces that are said to be bookmatched because they open like the pages of a book. When the two pieces are joined, as the two on the right will be to make the guitar back, you get virtually identical grain on either side of the center seam. This is aesthetically pleasing, and also separates guitars made from solid wood from those made out of laminates.
I can adjust the drum height almost infinitely with the wheel on top of the sander, so I can take off wood literally the thickness of a hair if I want.
I run each piece through repeatedly, until I get within several thousandths of my desired thickness - around .095" for the sides, and about .115" for the back plates.
Before I glue the two halves of the back together to make a single plate, I need to join them. Joining is the process of planing the two sides to be glued to the point that they are as close to flat as possible. Ideally, when you hold the jointed halves together, you should not be able to see any sunlight through the seam - before gluing!
There are lots of ways to do this. Some people use a long jack plane and a shooting board. I even know some people who use a flat piece of plate glass and fine grain sandpaper. I prefer to use my Delta Variable Speed Bench Jointer. Like many of the tools in my shop, this is a very dangerous piece of equipment. In the picture above, I've taped the two halves of the back together, and I'm running them over the 10,000 RPM knives rotating under the flat bed of the jointer. The red finger guard likes to believe that it is protecting me, but I know better. I keep my fingers well away from the business end of this tool.
After two or three passes, the joint is pretty clean. It's time to glue!
This is my joining board. It's very simple. I clamp two straight edges on either side of the board. Then I place the two halves of the back to be joined between them. I use wedges on the left side of the board to provide the clamping pressure.
Long-time luthiers will claim that - if you've properly jointed the two halves - no clamps should be required. Call me cautious, I guess. I don't use a lot of clamping pressure - just enough to assure that the joint is closed.