Lowering a Guitar Bridge
Source: Guitar Bridge Repair
Lowering a Guitar Bridge:
As a guitar ages, especially a guitar with a non-adjustable neck, the guitar neck tends to pull upward a bit, causing the string action to become somewhat higher.
This process can take many years or even decades, but it will almost certainly happen. The reason for this is the constant and relentless action of the guitar string tension.
Sometimes this action will be accelerated by exposure to hotter than normal temperatures or humidity.
The above happened to me. I had my favorite guitar for a long time and the neck was rock solid for years. Believe me it never budged. I took the guitar to Hawaii for 2 years and at the end of the 2 years the neck moved slightly. This was not a lot of movement, but it was enough to make an incredible playing guitar just an average playing guitar and I was not happy.
Now I know that I really didn’t need to perform a neck reset as the movement was not that great and when it got back to the mainland, the process stopped.
The next likely fix is to lower the bridge to restore the string action – and that is what I did.
Inspect The Guitar:
First you should make sure you are dealing with a shifting of the neck here and not a deeper more repair intensive condition. There are a number of articles that speak to this on this blog, so I won’t go into them at this time.
Make your measurements to determine how much to lower the bridge/saddle. If you make your measurements at the 12th fret, you need to double the measurement at the bridge because it is twice the distance.
Measure The Action Difference:
Lets just say for example that you have determined that you need to lower the bridge and saddle .75 mm to bring the guitar back to your desired playable condition.
Measure the thickness of the bridge in front of the saddle. Lets say the bridge measures 6.3 mm. If the saddle is at an ideal height and there is not any room to lower just the bridge, then we need to plane down the bridge.
If there is a bit of leaway to lower the saddle as well, you may be splitting the dimensional difference.
Prepare The Guitar:
It is an absolute must that you protect the top plate of the guitar because you are going to do some major work on the bridge. Make a template from illustration board with a bridge cutout, or better yet, use 1/16″ polystyrene plastic. Tape the protection piece in place on the guitar top.
Plane Down The Bridge:
The quickest way to lower the bridge and take major of amount of material off the top of the bridge is to do it with a portable belt sander. This is also the easiest way to ruin your bridge if you are not an expert with this tool. It is best to go at it very slowly and make slow long strokes and check your work often and don’t use coarse grit sanding belts.
The less hazardous way is to take the bridge down with an cabinetmakers quality low-angle block plane, such as the model I recommend by Leigh-Nielson. This tool has to be sharpened perfectly and that is no small task either. Adjust the plane to take off a nice very thin curl of wood.
First try one direction with the plane and if you get chattering and grain pull-out, you should try planing in the opposite direction. If you still experience problems, you are trying to take off too much material or the blade is not sharp enough.
The Final Steps:
When you have about .25 mm left to go, take a sanding surface and sand to the final thickness.
If needed, route the saddle channel deeper to make provisions for the saddle. This may negate the need to lower the saddle as well. This can and should be done with a Dremel Moto Tool and a saddle routing jig. (more on that in later articles.)
Make the need corrections to the countersink of the bridge pins if you desire this (and you should). Also make your string ramps from the bridge pin to the saddle. This eases the string around the corner of the pin hole to the saddle and minimizes string breakage. This can be done with the Dremel too. I would use 2 or 3 different bit sizes to make graduated slot widths for the different gage strings. (Refer to the diagram at the beginning of this article.)
Ultimate Guitar Repair Tip: To make the saddle the proper height, you need to have the angle of the strings from the bridge pin to the top of saddle neither to steep nor too shallow. There is a magic angle here that we will discuss in the Making a Guitar Saddle article.
Tags: Guitar Bridge Repairs, lowering a guitar bridge, lowering string action, string action
