Tools and Materials Required:
Woodworkers Marking Knife
Wood Chisels
Japanese Pull Saw
1″ Elastic Tape
Inside Form
Fitting the Guitar Back:
This article applies equally to the Acoustic Guitar as it does to Classical Guitars. Fitting the guitar back is a very tedious job. You have to be very precise so everything will fit together like a puzzle. It is of utmost importance that you align all of the joints, braces and channels to have a back plate that can be glued in place using minimal mechanical pressure.
First, you should make sure that your guitar back plate is ready to install and is completely finished, sanded and everything looks in order. One last thing you may want to do is to attach your luthier label to the inside of the guitar back. This is the easiest time to do this, while you have access to the back.
Make sure that the linings are glued in place to receive the back plate and the sides have be shaped – at least rough shaped for the contour of the back.
Initial Fitting:
Slip the sides into the Inside Form and make sure the top is dead flat on the bottom surface of the form. Make one final inspection to the back and make sure all surfaces are silky smooth.
Lay the back on the sides. Your back braces should extend over the sides slightly or be slightly long. Take a length of 1″ Elastic Tape and secure the back to the sides with a couple of loops around the Inside Form and tie off the tape. The back should be loose enough to make minor position adjustments, buy not so tight as it can’t be moved.
Line Up the Back Plate:
There is a global center-line for the guitar. This center-line is the dead-on center for all parts of the guitar used for alignment and it should be clearly marked on the Inside Form. The back plate should be aligned on this center-line and it also should be lined up perpendicular to the this global center-line.
Mark the Brace Locations:
Take a Woodworkers Marking Knife, and mark all of the brace locations. Mark on either side of the brace and strike a sharp mark over the top of the lining and the side. At this time it is also import that the ends of the back reinforcement strip are trimmed to the correct length. You can to this by gently turning the inside form over and reaching through the access hole and mark the head and tail block location right on the reinforcement strip, so you know how much to trim the reinforcement strip.
Once marked, take the Fine-Toothed Japanese Pull Saw and carefully cut down through the strip without cutting into the back material. Now take a 1/2″ Woodworkers Chisel and chip out the scrap, clean the remains of the strip and the glue holding in place and make this area smooth and ready for gluing.
Acoustic Guitar: Cut Brace Ends Into Sides:
The method of attaching the back braces to the sides differs from the classical guitar and the acoustic guitar. The acoustic guitar method of attachment is to cut the very ends of the back braces through both the lining and the sides of the guitar. This means that the braces have to be shallow enough at the ends so they can be covered by the guitar edge binding. Otherwise you will be faced with a unsightly gap in your guitar sides.
The method I use to cut these grooves is to mark the depth of cut carefully on the guitar sides. Then take a very Fine Toothed Japanese Pull Saw and carefully cut on your marks down to the depth marker for each brace. Now take a very sharp 1/4″ Woodworkers Chisel and cut away the wood, until all the braces fit. Check the back fit frequently and adjust as necessary.
Classical Guitar: Braces Let Into the Lining:
The method for attachment of the classical guitar back to the sides is to actually trim the braces carefully to length so they fit tightly against the guitar side wood. As with the Acoustic Guitar, carefully mark the brace locations. Now mark the Depth of each brace end on the inside of the lining. I usually trim a piece out of the lining the entire depth of the lining. Do this with a Fine Toothed Japanese Pull Saw. Now take a 1/4″ Woodworkers Chisel and carefully chip out the scrap lining.
One Final Fitting:
Fit the back and adjust as required. Trim the back reinforcement strip as required to fit tightly against the foot and the tail block. Fit the back one more time. This time loosely strap it down the the 1″ Elastic Tape and check that it is lying flat against the linings and sides, without any gaps.
Also check that the classical guitar foot is tight against the back and that the head and tail blocks of the acoustic guitar are a tight joint too. Make sure there is not a hump in the back where the plate lies on the head and tail block. If there is, trim down with blocks with a Sanding Surface.
Ultimate Guitar Building Tip #1:: I prefer to use the classical guitar method for acoustic guitar back too – take a look at the photo at the top of the article. I feel it is a better construction technique.
Remove the back and you are now ready to glue the back to the sides.
Tags: fitting the guitar back, guitar back construction, Guitar Building Articles, how to make a guitar, how to make a guitar back
