[Guitars44me]

Originally Posted by Tim McKnight

Hi John and GR14,

Differential Relief is a term that was coined by David Collins of Ann Arbor guitars. He teaches a method of sanding a gradual and transitional relief into the fret board wood. In simplest terms it goes from perfectly flat on the treble side and then transitions to a concave center relief on the bass side. Its one of those mojo techniques that is difficult to put into words and is best taught to a person one on one. He occasionally holds a two day class in his shop in Ann Arbor which I HIGHLY recommend to anyone wanting to improve their set up skills.

Prior to taking their class I was able to set my actions, to what I considered, pretty low but after the class I can set the action significantly lower without buzzing. I had never been able to achieve this low of action before, without fret buzz, which continues to amaze me. I am not bragging on me but rather tooting David's horn and the set up skills he teaches.

The first guitar I built, after taking the class, our customer spec'd medium gauge strings on the guitar with comfortable medium - low playing action. I delivered the guitar with mediums on it and he asked if I forgot to put mediums on it? He thought the strings were light gauge and commented that the guitar played better than any guitar he had ever played, and this gentleman is a guitar teacher and has played a LOT of guitars. All the guitars we have built since we continue to get similar positive feedback.

One of the pictures above shows me putting red marks on the crown of the frets. When I put the (400 grit) sanding beam on top of the frets, I barely move it back and forth a couple of VERY LIGHT strokes then lift it and inspect the top of each fret. What I usually see is some very light faint scratches in the red ink. Its rare now to see any ink totally removed or even a slightly flattened fret that requires re-crowning. This final step confirms the wood is where its supposed to be and that each fret is seated to the same and consistent depth.

This is a method that one cannot achieve perfection if you fret the board before gluing it to the body. Its difficult to explain why not unless you see the technique actually being done in person. It requires the neck to be attached to the body and then you have to systematically load, unload and / or support the neck while sanding different planes of the FB.

The first FB I did this too, while in class, took me MANY hours of sanding. Maybe ~6 hours of sanding and checking and chalking and sanding and checking and chalking ... It doesn't take me that long now that I have more experience but that first one was brutal to get the technique and method right. I only wish I would have done this 25 years ago.

This is BOSS. For those of us who may well play four or five sets in a day, a hundredth of an inch off the string height can be a big help. Thanks Tim.

You are a font of cool info!

Paul