Matthew here and greetings from the repair bench! I’d like to take the opportunity to share a luthiers trade secret on how to repair over cut slots on a bone nut. This fix is extremely useful and fast to perform and has helped me out on countless occasions over the years. The causes for an overly deep nut slot can come from a myriad of factors including: truss rod adjustment, accidental damage or chipping of the nut, or just plain old wear and tear. I DO NOT recommend this repair to be done on any material other than bone and should only be performed by a capable tech. So let’s dig in…
Step 1: First thing to do is to mask off the areas around the nut. The preparation is critical as it will prevent the glue from wicking onto the finish possibly causing permanent damage. Once the area is masked off, loosen the strings, pop them off the nut, and pull them aside get them out of the way.
Step 2: Now that the area is masked and the strings are pulled aside, the next step is to pack the nut slots with baking soda (Sodium Bicarbonate). It is important to pack the slots tightly so I often use the back edge of an X-Acto knife to force the baking soda into the slots.
Step 3: Once the slots are packed full of baking soda the next step is to CAREFULLY wick thin superglue into the filled slots. I use Teflon micro pipettes for this operation as they allow complete fingertip control to applying the glue. Once the glue is applied to the slots allow the glue to set for approximately 10-15 minutes.
Step 4: Once the superglue has set, you’ll notice that the baking soda has become as hard as the bone nut. At this point, I file the nut slots as per the standard method and continue with the set up.
Step 5: The completed nut!