Making a Bone Acoustic Guitar Saddle
What is an Acoustic Guitar Saddle?
The saddle is a crucial part of an acoustic guitar. The thin white strip protruding from the top of the bridge serves several functions. Not only is it responsible for transmitting the vibration of the strings to the guitar top, but it also helps to control the instrument’s string action and intonation.
The saddle can be made of many different materials. When replacing one, we have to consider a number of factors. Sometimes a prefabricated saddle can be shaped and fit to an instrument. However, if the desired sizing and material are unavailable, one must be cut by hand. We have written in greater detail about the different materials available for both nuts and saddles in our previous blog post: string nuts. For this article, we will be focusing on the process of hand cutting a new saddle out of bone.
When to Replace an Acoustic Guitar Saddle
The saddle pictured at left is ready for replacement for several reasons. Any one of these alone is reason enough for replacement. For starters, this saddle has been replaced before and the one chosen is a poor fit for the slot. There is a large gap between the end of the saddle and the edge of the slot.
Its profile is also too flat to match the curvature, also known as the “radius”, of this instruments fingerboard. The reason this matters is because the mismatch results in the string action being uneven across the fingerboard: the strings in the center are closer to the fingerboard than the strings on the outside edges. Lastly, besides not sounding great, this cheap plastic saddle has large grooves that have been worn into it by the strings. Besides the obvious effect on the string height, these grooves also move the strings contact point and negatively impact the instruments intonation.
Proper setup will not be possible unless this saddle is replaced. We are going to upgrade it with a hand cut, compensated bone saddle. What follows is broad overview of the work involved. While I would not recommend that you attempt to cut your own saddle using only this article as a reference, hopefully you will walk away with a better understanding of the meticulous work involved in doing the job properly. If you enjoy this post, you might also like our post about making a bone string nut.
How to Make A Bone Saddle
First I find a suitable bone blank. In this case I am using a piece of bleached bone that I have determined is sufficiently oversized so that we can cut it down to fit my needs. I buy these in bulk from a distributor. To begin shaping it, I use a caliper to measure the length of the saddle slot. I then transfer this to saddle by drawing a line with a pencil. Next I will take the saddle over to my bandsaw to rough cut the length. I make sure to cut outside of the line so that I can dial it in to match the rounded edges of the saddle slot later.
Fitting the Saddle to the Slot
After the saddle has been rough cut to length, I begin fitting it to slot. Using sand paper on a dead flat surface, I carefully sand both sides as well as the bottom of the saddle to make sure that they are straight and true. Then I take off any remaining material necessary to get a snug fit in the saddle slot. Once my width is about right, I will carefully round the edges of the saddle so that it can pop perfectly into the slot. This process definitely takes some experience to get right. A correct fit should be snug, but not excessively difficult to remove. I will typically fit the saddle just a touch looser on guitars with under saddle pickups in order to ensure that it is able to make solid contact with the transducer.
Radiusing the Saddle.
Next I use a set of radius gauges to draw the profile of the fingerboard onto the saddle. I can then take the saddle over to my disc sander to sand the radius into the top. If I were making a traditional non compensated saddle, I would simply round over the edges at this time to make a nice rounded top. But, since we are compensating this one we have an extra step.
Compensating the Saddle
Compensation is a term used to describe adjustments made to the functional length of the string in order to adjust the intonation of the instrument. To compensate the saddle, I begin by using a pencil to mark the area between the second and third strings. Since this is where the strings transition from plain to wound, this is the point that requires the most significant change in compensation in order for the guitar to intonate properly.
Basically, I want the first string to leave off of the front of the saddle. The second string should leave the saddle a little further back than the first string does. Then I want the third string, the first wrapped string, to come forward again and leave off of the front of the saddle. The rest of the wound strings will then progress backwards, with the sixth string leaving off near the back of the saddle. To accomplish this, I use a pencil to draw two lines diagonally across the length of the saddle. These lines will be my guide of where to file. I then shape the top of the saddle, removing material on either side, until the desired compensation has been achieved.
Setting the Saddle Height
Now that this thing is finally starting to look like a saddle, I put it back into the guitar and string up the outside strings. This allows me to take an action measurement. Since I purposely used a blank that is taller than I need, the strings will predictably be too high off of the fingerboard. The saddle will then go back to the sander to have the excess material removed from the bottom. Once the proper height has been achieved, I will true the bottom of the saddle to be sure that it sits evenly along the bottom of the saddle slot. This ensures the best sound transmission to the top.
Polishing the Saddle
The work isn’t done yet! Once everything is dialed in and functioning the way I want, I run the saddle through a couple of grits of fine sand paper to polish off any tooling marks and then I use a small buffer to polish it out to a high shine. Not only does this make the saddle look great, but it also provides a nice smooth surface for the string to rest against. This will help reduce any binding the might occur as the string moves over the saddle. With that completed, the saddle is ready to go. Its time to get the rest of the strings on the guitar and make some music.
Compensated Bone Saddle Installed
About Guitar Repair Long Island:
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