Guitar Building Techniques – Plate Joining & Book-Matching
Two guitar building techniques that are used over and over throughout the guitar building process are plate joining and book-matching. Plate joining is the method of edge joining two pieces of wood. The edge faces of two pieces of wood are glued together to create a wider board. On a guitar plate joining is done on the top and back of the guitar to create the necessary width. Done properly it can be a very strong joint. Done poorly it can mean disaster for your guitar.
Two pieces of wood can also be edge joined to create a mirrored visual effect. This technique is known as book-matching. This is an age old woodworking technique and a guitar building technique that is used by almost all luthiers. A nice visual can be achieved by matching the face grain of boards that were cut in adjacent sequence when milled. If this is planned and executed right it can produce a quite striking effect. This technique is often used to create headpiece veneers.
Bad joinery is a tell-tale sign of an amateur guitar maker. The joint on the top and back of the guitar must be perfect to avoid problems with the instrument down the road. Poorly executed joints can separate as the guitar ages. Exposure to drastic changes in humidity can accelerate the disaster.
Plate joining is easy and can be done without any expensive tools or gadgets. All you need is a plane, a flat piece of plywood, and some wedges. There is a video below showing you how. Read on, there are also instructions on how to make the fixture.
Guitar Building Technique You Must Perfect – Plate Joining Tops and Backs
Because plate joining is most commonly done on the top and back of the guitar, it is a guitar building technique you simply must perfect. The structural integrity of the guitar depends on these joints. The two halves must make perfect contact at every point along the edge with no gaps.
Both the guitar soundboard and back are relatively thin at the stage where you will begin to join them. The thinner the pieces are the harder they are to join without ending up with backs and tops that are too thin. After joining there will be clean up so it is recommended to thin to within about .030″ of the final thickness before joining. This way even if you need to remove a fair amount of wood to clean up there will be enough left to still make the desired final thickness.
The fixture used for edge joining is easy to make and is fully described in the next tab.Apply the glue to one edge. Bring the two edges together on the fixture.
Fitting the Joint
The key to edge joining is the fit of the joint. Always mark a cabinet makers triangle half on each piece for consistent orientation. If you have a joiner run the edges over the joiner to straighten the edges. If you don’t have a joiner score a line along each edge and plane straight with a hand plane. I prefer this on pieces that are really bowed along the edge to minimize the amount of material necessary to remove.
When fitting the joint with a hand plane make sure the blade is sharp and only take the finest shaving taking any more with each pass will only result in frustration. Trim one piece face up and the other face down to negate any skew in your plane blade. Put the pieces together with little to no pressure and hold up to the light. Sight for spaces. If there is the slightest space go back and trim until you see no light. For wood that does not plane well, or if you see you are pulling up grain along the edge use a sanding block to final trim.
Once the joint is perfect clamp down the outside piece with the movable cleat and place a clamp on the other side of the fixture for stability. Whenever you are edge joining on the fixture always place a piece of wax paper underneath the joint to prevent the glue from sticking to the fixture. Apply the glue to one edge, place the pieces flat on the fixture. Rub one half back and forth against the other until it becomes difficult to move. Then put some pressure on the wedges. Take a piece of hardwood with a clean edge and rub it along the joint while pressing down. This will clean the glue and correct for one side being too high. To keep the wood from cupping with added pressure place either place a weight or clamp a piece of wood over the exposed half to keep it flat. Tighten the wedges and you are done.
A Simple Edge Joining Fixture
This edge joining fixture for joining guitar tops and backs is very simple and easy to make. Below is a list of materials for making the fixture:
- 1 piece of 1/2″ plywood 24″ x 22″
- 2 pieces of 3/4″ (plywood or solid wood) 2 1/2″ x 22″
- 6 hardwood wedges
The best plywood to use for this type of fixture is Baltic birch or a 9 layer plywood – this stuff remains flat best. As far as the size of the fixture goes you can certainly make the fixture any size you like but it should at minimum be just a couple of inches longer and wider than the width of your guitar top, and remember to add for the width of the fixed cleat. You will need two 2 1/2″ wide cleats.
The cleats can be made out of plywood or solid wood but they must be rigid 3/4″ stock is recommended. One of these cleats is fixed, permanently attached to one edge of the fixture, the other is movable or unattached.
The wedges are best made of solid wood and can any angle less than about 30 degrees, mine are about 20.
Guitar Building Uses for the Fixture
This fixture will enable you to join tops and backs as well as headpiece veneers. If you use my method of using a thick headpiece veneer on top of the stack you can book-match two pieces of figured wood for graphic effect using this fixture. I have created a smaller version of this fixture just for this purpose. The fixture is shown in the photo on the right. Gluing the headpiece veneers or any small pieces of wood is easier in a small figure like this. Everything works the same but its size enables the use of clamps, eliminating the need or a movable cleat.