The neck on this Hofner Colorama was originally quite badly back bowed, as shown here:
In an effort to rectify this, we’ve tried three different approaches, as follows:
1. While re-radiusing the fretboard, more pressure was applied towards the middle of the neck in order to remove more fretboard material in that area. This would not straighten the neck, per se, but it would reshape the top of the fretboard in such a way that its top would end up being flatter.
2. When refretting, the fret slots were widened. When frets are forced into narrower slots, this has a tendency to force the neck to back bow, so we wanted to avoid this at all costs. The slots are still narrow enough to grip the new frets, but are certainly not overly-tight.
3. Obviously the truss rod nut was slackened as much as possible. In fact, even with the nut removed, the neck still maintained a back-bowed shape. It was noticed that the washer under the nut was wedged into place, and it was suspected that it might be preventing the truss rod from properly slacking off. In other words, when the truss rod nut was tightened, the truss rod threads would pass through the washer, but when the nut was loosened, the threads might get stuck in the washer, leaving the truss rod in a tensioned state.
After some time, the neck appears to have straightened out enough that we can consider doing a fret level and crown.
First, we tape off the fretboard, leaving the frets themselves exposed:
Then we find something nice and straight with a flat bottom. Don’t assume straight tools are actually straight, by the way. This spirit level has been confirmed as being straight enough for this job, and 400 grit sandpaper has been stuck along the bottom edge.
We then mark the frets with a “Sharpie” pen or similar:
Then we run the leveling tool up and down the fretboard, parallel to the neck, making sure to keep it straight, and giving each area (left to right) the same amount of attention.
It soon becomes evident which frets are sitting high/low compared to others. We need to keep doing this until the top (center line) of the black marks is gone on every fret:
Next, we make the frets black again, and run a radius sanding block up and down a few times until the tops of the black marks are gone on every fret again. This is to ensure we haven’t inadvertently reshaped the curvature of the frets in the previous step.
Now we blacken the frets for the last time and use a needle file to file the edges. Here I’m using a fretboard protector for a little bit of extra protection:
What we are doing here is rounding the edges of the frets again. However, we need to make sure that we don’t affect the heights of any of the frets, so we leave a thin black line along the center of the frets, as follows:
Next we run some thinner sandpaper up and down the frets briefly to help round the frets just a little more. I’m actually using a 1600 grit Micro-Mesh Soft Touch Finishing Pad from Stewart MacDonald (http://www.stewmac.com/shop/Fretting_supplies/Polishing_and_abrasives/Micro-Mesh_Soft_Touch_Finishing_Pads.html):
Finally, some steel wool is used to polish up the frets a bit (I’m using 000 here, although 0000 would give you an even shinier finish):
And here’s the end result. A super-flat, shiny fretboard. I can’t wait to use it.
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