When you brought home your guitar and got its initial set-up done, the tech guy ensured that the numbers (measurements – action, relief, nut action, etc) added up. That made your learning and playing a breeze.
Now your beloved acoustic guitar is 7 – 8 years old and you have religiously played it almost every day over this time. Excellent!!
However, you notice that ‘pits’ are developing in the frets exactly at the spots where the strings hit against the frets. For those getting apprehensive, fret not. This is normal wear and tear that every instrument – acoustic or electric – goes through if it is ‘played’.
Just like a pothole in the road, the erosion starts slow till the pits are so deep so as to catch strings in them and affect your playing.
So, what is to be done? Fret-levelling!
It is tedious, time-consuming process where a level surface (like the one in the picture below) is run along the fretboard with sandpaper on the contact surface and rubbed till the ‘pits’ are rubbed out of the surface.
pix courtesy: guitarrepairbench
Then follows more work in putting the ‘crown’ back in the frets and bringing them up to a mirror-like shine. But that entire process, I feel, I should reserve for another post. Suffice it to say that after a proper fret job, your frets should look brand new. Much like this:
You string ‘er up and start to play but the guitar is not responding the same way as it used to. Yes, the frets are fine but the action at the nut (1st fret action) has increased.
Let me explain. The action – at the 1st fret and at the 12th fret – was initially set to the original-sized frets. When you tried to take the ‘pits’ out of the frets, you removed material from the frets, lowering them. However, the nut remained at the same height!
Thus, the increase in action at the 1st fret. If you need to get the old action of the guitar back, you will have to lower the slots of the nut so that the strings sit lower, bring the action down.
Most people will tell you that all you need to do is deepen the string grooves and all would be well. Like this:
I say ‘No’! If you lower the slots in the nut, will your strings sit to the prescribed depth: half in the slot and half outside it? Like this?
NO! NEVER! The way out, then, is to knock the nut out of its groove and sand its bottom, just like you would a saddle, to lower the action. A little at a time does the trick!
You can loosen the strings, pull out the nut and re-sand it, but if you overshoot the desired nut height, you will have to replace the nut.