I was commissioned to re-fret Guitar. I am not sure of its provenance. The headstock has the Fender logo and the Stratocaster name but there is no serial number and no indication of its country of origin. It has seen much action and the frets testify to the fact. (I wonder why they have worn mostly at strings 2 and 3? Bending perhaps.) Its owner likes a fairly low action and to achieve it without buzzing requires the frets to be in good order. I expect it would have been possible to stone the frets to achieve buzz-free playing but the remaining fret height would have been low. The frets were all good and tight.
The first job was to measure the set-up as received. I used a dial gauge instrument to measure the string clearances at the first and 12 frets. The neck deflection was also measured both with the strings on and off. The results are below. I guess neck deflection does no mean much with the frets worn as they are
String 1 2 3 4 5 6
Ist Fret 17 20 19 11 21 18
12th fret 56 56 59 61 50 57
Neck deflection, strings fitted, head and neck unsupported: -0.007 in.
Neck deflection, strings off, head and neck unsupported: +0.003 in
Removing the frets is a tricky business. In my experience, it cannot be done without some fretboard damage: small chips dislodged near to the frets. I use a pair of end-cutters ground so as to get beneath the fret and lift it with a wedging action. Done with care, the chipping can be minimal and hidden beneath the new frets. Sadly, I did not quite achieve perfection on this occasion.
Next, I cleaned off the lumps and bumps left by the fret removal using abrasive paper, then measured the curvature in many places. Not surprisingly, it was not consistent. From the nut to the 12th fret it had a radius of 12 inches but beyond that it decreased, being about 10 in radius at the 21st fret. If it was intended to be a compound radius fretboard, the maker had got it wrong. The radius of curvature should increase towards the bridge, not decrease. However, I have seen this defect before and suspect it may be caused by the ageing process and the stresses on the neck. In truth, it is unlikely that any player would have noticed. Nevertheless, I spent an hour or so sanding the neck to conform to the 12 in radius gauge and be straight throughout its length. On the subject of sanding a fretboard, I have noticed the proliferation of radiused sanding blocks in instrument makers suppliers catalogues. I have to report my own poor results with such tools. The curvature I have achieved with these has been tighter than the block, presumably because I failed to keep be block axis aligned with the neck axis. I find it better to use a regular sanding sticks (abrasive paper stuck to flat wooden sticks with double sided tape) and frequent testing against a straight edge and the radius gauge. I finished off with 400 grit paper on a cork block.
Installing the new frets
I selected the fretwire and set the fret-slot-saw depth stop and the performed a trial fret on a piece of scrap hardwood. This is an important step as cutting the slots too shallow means that the frets will not seat properly. Too deep weakens the neck. Then I re-sawed the fret slots. Fortunately, the originals were narrower the required by the new wire. The neck was re-sanded to remove the marks left by the saw depth stop. Then the fretwire was bent.
This is my fret bender, home made and not quite finished, it needs a screw arrangement to set the bend; and it has improved my fretting performance no end. It is quick and easy and gives perfectly consistent bends. I over-bend the wire to 8 in radius.
Here is the bender close up. the top, driven wheel, which is grooved for the fret tang, is on a slide so the bend radius can be adjusted. The bearings are ball races throughout.
For this job, I undercut the frets, as would be done for a bound fretboard. I did it here to minimise the filing required and hence the marring of the finish in that area. The undercutting was done using flush cutting end cutters, my fretwire cutters. No filing was necessary.
The fets were pressed,not hammered. I have a modified bearing press and a selection of radiused cauls. I performed the fretting in two passes: first with and 8 in radius caul and secondly with a 12 in one. After pressing the frets, out of interest,I measured the neck deflection. It was +0.002 in. The process had caused the neck to bow backwards slightly, presumably because of the wedging action of the fret tangs.
Here are the completed frets with the ovehang clipped off with fret cutters.
Filing the Fret Ends
It is vital to the feel of a guitar that the fret ends are smooth. If they rip lumps out of the players fingers, the job and the luthiers name will be mud. I first angle the ends with a small mill-cut (circular saw file) file held in a wooden block at an angle of 35 deg. from the perpendicular. This file is worked until the fretboard takes a slight chamfer throughout its length. Because I undercut the frets, there is no protruding fret tang to be filed off, an operation that would cause considerable damage to the neck finish. After chamfering, the burrs are removed and the corners rounded with small files. I have a selection of these that have one edge ground smooth so that they do not damage the fretboard. Even so, considerable care is needed. Finally in this operation, I replace the file with an abrasive board, a strip of plywood with 400g wet and dry glues to it.
Stoning and Crowning the Frets
With pressed frets, the crowns heights are very consistent. Nevertheless, I dare not leave them un-stoned. I keep a carborundum stone specially for this job and flat it beforehand on a diamond whetstone. The idea is to remove as little metal as possible but touch all of the frets. In this case I had to remove a little more because of slight damage to one of the frets. The stone is worked slowly backwards and forwards leaving a roughened line along each fret crown. I was unable to get an adequate photograph of a stoned fret so you will have to imagine one. It is important that the stoned surface is easily visible so that the crowning job can be performed adequately. On the other hand, the stoned surface must not be rough such that significant material has to be removed to smooth it, as the accuracy would be lost.
The crowning is performed using a file of some sort. My preference is for a triangular saw file of about 10 inches long with the corners ground off. Fortunately, my favourite is also the cheapest; that is if you grind off the corners yourself. The most expensive is a diamond coated file shaped to fit the fret. Middle of the road is a conventional file with a convex cutting surface. I have one and it is ok when a lot of material has to be removed but the three cornered file is my choice. The idea is to leave a very thin stoning line at the top of the fret and to reshape the fret to something like its original form. The photos below show the crowning file and the file in action.
The final operation in the re-fret is the polishing of the frets. Fine wet-and-dry with a smear of oil removes any file marks and a high polish is achieved with a felt wheel mounted in the Dremel. Some care has to be taken in this process: if the fret becomes excessively hot, it may well spring out of its slot. Metal buffing polish provides the abrasive.
It is inevitable that, after a re-fret, a new nut will be required. Making a nut is a significant job that has to be executed with precision. A nut should be a push fit in its slot and ought not be glued. Two thousandths of an inch makes the difference between a good fit and a loose fit The string slots have to be in the right places and their depth is critical. I make nuts from cow bone from the local butcher.
I replaced the strings and tuned to standard tuning and set the truss-rod to give a 0.002 inch bow in the neck as measured with a dial-test indicator and then set the string clearances thus:-
String 1 2 3 4 5 6
Ist Fret 15 16 17 19 21 22
12th fret 56 56 56 56 60 62