Fret Wire Preparation

Bending the Wire

Now that my board is prepped I go about preparing the fret wire. Above you can see where I've bent the wire to match, or actually slightly exceed, the radius of the fingerboard. This helps the fret seat nicely as they have a desire to "spring" when tapping them in.

On bound fingerboards each fret tang must be cut to the exact width of the fret slot so it can sit neatly within the binding. The crown of the fret often overlaps the binding, though there are exceptions (Les Pauls, many mandolins and those incorporating fingerboard binding nubs, read more here. ) This process requires far more time, hence the reason you will pay more to refret a bound fingerboard.

On Bound Fingerboards the fret's tang must be cut back to fit snuggly between the binding while the crown is left to overhang the binding.

Fret Slot Width vs. Fret Wire Width

Measuring the fret slot.

With the board  repaired / planed / sanded and shaped to the proper radius the fret slots can now be measured to determine their depth and width. If a considerable amount of wood has been removed, deepening the slot will be necessary to insure the new frets will seat properly in place. A slot that is too shallow will cause the fret tang to hit bottom before the crown of the fret can sit flush against the board. And if glue was used on the previous fret job it's important to completely remove it from the bottom of the slot. Tiny bumps of old glue left hidden within the fingerboard slot can cause resistance when seating the new fret and will have to be removed before it will seat properly. Removing crusty old glue from a bound fingerboard can be quite time consuming as the use of a saw is a dangerous proposition. For this task I may use the hooked tool in the picture below to slowly scrape old glue out.

Cleaning Fret Slots on Bound Fingerboards

Fret Wire Size
 

A well seated fret leaves no gaps between it and the fingerboard and can not be lifted without the use of pliers (or bionic fingers). Not only do we want the crown to seat firmly against the fingerboards surface but we want the fret tang to fit snuggly within the fret slot leaving no gap which could weaken the necks rigidity.
What's most important here is to choose a fret wire who's tang will adequately compress the slot and provide a firm grip. We are talking about tang size here, not crown size. (Tang size does not dictate crown size and vice versa.)

Oversized Fret Tang

Since oversized fret tang is useful for fingerboards that have had numerous refrets or require wedging, it is best reserved for those cases. Meaning...I would never purposely increase the size of the slots in the fingerboard in order to use a fret tang that is too big for the job. While fret wire with larger tang is available, there is a limit to the sizes. Each time the fingerboard slot is widened we must then use a fret wire with a larger tang to provide good compression. If the fingerboard slot width exceeds that of the largest fret tang available we must resort to other means to provide adequate compression. Use of the appropriate wire insures a longer life for the board.