4. Glue a slot, place fret and press home completely
There are other possibly faster and easier methods of course but this is how I learned from a pro.
Take an old wound string, top end, hold it on the wound length.
Drip a few drops of glue (consruction type which dries up hard not gooey) on a piece of scrap paper.
Scrape a bit of glue on the unwound part of the string, and move it into the first slot. Wriggle to and fro to ensure that glue is in the slot evenly. Ensure that no glue is left on the top of the fretboard.
If that happens by accident immediately remove the glue with a kitchencloth.
Prepare some 5 slots with glue. This is the number of frets you can handle in the next two steps without the glue hardening too much. If you’re less confident do three.
Carefully maintaining the sequence of the prepared frets now take one and place it straight in the slot. If all is well the radius of the fret is slightly smaller than the fretboard.
Using a small hammer to lightly move the fret to be right in the middle of the fretboard.
Now softly using a small hammer drive the fret into the slot at the edges and a bit in the middle. Don’t drive the fret hard in the middle as that will cause it to straighten a bit, resulting in edges that refuse to remain in the slot nicely.
Some luthiers will use the hammer to set the frets all the way, but pressing as described below causes less damage and distortion.
Using a piece of wood and a clamp or a fretpress (In a vertical drilling stand, or use more expensive tools if you can afford them) press the fret well into the slot With rocking motions make certain that the edges are firmly pressed into the slot.
Make certain to support the neck under the fret you are pressing!!
5. Removing sharp ends along the sides and gluing the holes
Some (if not all) frets will stick out from the edge of the neck, in other words moving your finger alongside the neck will leave little pieces of skin – not what we want.
Use the 3-sided file (preferably a sweet or worn side) as shown in the pic and very carefully file down the nasty bits, avoid hitting the paint.
Once you’re happy with the edges (for example if you move your finger along the side it will not leave bloodied skin tissue), you will see that in some slots the tang is too short leaving a small hole.
Fill these with tiny drops of superglue. Little bits at a time, and repeat until it looks ok. This takes some time as you have to wait for the glue to harden.
This will not only nicely fill the hole, but also creep further into the fretslot and help fixing the fretends in place.
When completely dry remove the excess glue (some is unavoidable) with a flat file
6. Levelling and crowning
This set of steps can be executed separately in order to reshape existing frets if some are worn, but in general enough material is present. This would be called a ‘fretdress’
Using a three sided file (25 to 30 cms long) without wooden handle, file with long moves in parallel with the axis of the neck. Frequently (the more the better) check if all frets are hit completely. If a fret is not completely visibly hit continue leveling.
When all frets are visibly touched by the file repeat the filing but now perpendicular to the axis of the neck paying attention to the edges by following the radius
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After the previous exercise all frets are even, however the tops of the frets are somewhar flat. This would cause an uncertain touch with the strings. We want the fret as round as possible whilst still being completely level.
YOu need the special crowning file for this.
Holding the file at a small angle treat first the left and then the right side until you see a thin (untouched) line just on the top of the fret. Good lighting here is essential. Don’t touch the top of the frets , only the round sides.
Use a fretboard protecting material, plastic or metal so you can polish the frets but not the wood.
Polish with a very very fine material