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Trem to hardtail conversion
<p>In this tutorial we will look at the work required to convert a guitar equipped for a tremolo system to one with a simpler hardtail style bridge.</p>
For this you will need:
- masking tape
- epoxy (or other stable wood filler)
- hand drill
Unlike a hardtail bridge, most tremolo systems remove a large amount of wood from a guitar's body. In order to retrofit a hardtail bridge this "missing" wood will need to be replaced in as seamless a way as possible.
The general process is to create rectangular recesses on both sides of the guitar's body into which blocks of wood matching the original body wood are glued and then trimmed flush. Although this tutorial provides the simplest and most straightforward method using the bare minimum of tools, there are many ways in which to achieve the same idea. By all means adjust the information presented to suit your own level of experience and equipment.
Start by measuring the total width of your guitar's body. Mask off rectangular areas around both the top and bottom of the tremolo cavity and measure the areas you have masked off.
Using a router or hand tools, remove wood from both the front and the back by half the guitar's depth on each side of the total body thickness. Try not to cut into your masking tape if possible and be sure to keep the sides as straight as possible while you're doing this.
Note: In this tutorial the routing was done freehand. Generally this is only recommended for those with both the confidence and experience in managing this. The scope of this article is not meant to cover all routing techniques, templates, guides, etc. Head over to the forums for specific advice relating to your own personal equipment and experience!
Cut out a matching block of wood big enough to fit each of the cavities you just cut out. Ensure that the direction of the wood grain also runs the same way as the body - down the length.
Tape the smaller one against the top cavity and using a pencil, mark where you need to cut and shape the block down from the back cavity.
Sand and trim your blocks until they have as perfect a fit as possible.
Ensure they fit flush with the bottom of the cavities. When you are satisfied there are no gaps you can glue in the blocks.
Plane and sand both blocks flush to the body once they have dried. Be careful not to allow the sander to dig into the block since you only want to level them at this point.
A common problem most people run into at this point is getting the blocks all sanded flush but finding gaps at the edges because the sander caused enough heat to shrink or loosen the adhesive or the blocks were undersized. This is not a major issue. You can fill the gaps and hand sand the wood back level once it is dry.
At this stage, if you primed the wood you would still more than likely notice nasty glue lines which would then show up in your finish. Even if you cannot see them at this stage, it would be seen during the differing seasonal movements of the wood.
The solution is easier then you think: cut a small groove along the seams of the joints (such as with a Dremel tool) and fill them back up with a batch of epoxy wood filler. Although still affected by heat and seasonal movement differently to the body woods it will not be seen as easily - if at all - through the final finish.
Make sure the filler goes all the way into and across the grooves. Gently smooth the filler away from both sides of the groove as opposed to in the direction of the groove to prevent filler "pulling up" from the edges.
Once it is dry, sand the filler back down flush using a hard sanding block to ensure flatness. If no more finish sanding is needed around the repair you can now prime the body and do any touch up work you may need. Using a long sanding stick helps to ensure flatness and to prevent heat buildup in the wood filler and joints.
Time to place the new bridge properly! Temporarily re-fit the instrument's neck (bolt it in properly as it may move in the neck pocket otherwise) and line a straightedge against it, draw lines extending both sides of the neck down the bout of the body. You can then then measure exactly halfway between these lines (just behind the neck pocket and at the rear of the body) to find your center line. Draw this in also as this will assure a perfect alignment of your new bridge.
Whilst you temporarily have the neck in place, measure the distance from the nut to the 12th fret. Mark this same distance on the body from the 12th fret onto the centreline just drawn.
To place the bridge at the point where the guitar can be comfortably intonated, adjust the bridge saddles to their minimum adjustment point (saddles closer to the neck). The point where the strings go over saddles should lay straight over the mark you just made on the centreline. Since saddle intonation is only done backwards from the neck, this step ensures you will get the maximum range of adjustment from your bridge.
Some models of fixed bridge have limited intonation adjustment range (such as vintage Tune-O-Matics) which may require additional compensation when calculating their mounting position. Usually this is done by moving the bass-side post back a small distance from the direction of the neck. If your bridge has less than 3/8" - 1/2" (10-12mm) of adjustment range, ask around on the forums for advice!
Mark where the mounting screws will be and pre-drill these points using a drill bit finer than that of the screw shanks (1/16" or 1.5mm - 2.0mm).
If you have a bridge that strings through the body, mount it now and drill out the holes through the body. Remove it and flip the body over to drill out the holes for your string ferrules.
Prime your body and don't forget to drill out the hole for your ground wire so that it can make contact with the bridge! Now pick a finish and go for it!