WHITE PAPER: A MECHANICAL ANALYSIS OF SPOT-LEVELING TOOLS
FretFixxer Vs Fret Kisser Vs U-File

WHITE PAPER: A MECHANICAL ANALYSIS OF SPOT-LEVELING TOOLS

EXECUTIVE SUMMARY
In guitar luthiery, precision fret leveling is critical to achieving low string action and eliminating localized string buzz. Traditional spot-leveling methodologies rely on flat-surface abrasives that prioritize material reduction over profile preservation. This paper examines the structural and workflow impacts of three contemporary spot-leveling instruments: the SixStringers FretFixxer, StewMac Fret Kisser, and MusicNomad U-File. The evaluation focuses on geometric integrity, process efficiency, and the post-leveling state of the fret wire.

1. ENGINEERING METHODOLOGY & PRODUCT ANALYSIS

SixStringers FretFixxer
    • Core Function: This tool serves as a concurrent spot-leveling and crowning tool. It is engineered to reference and span the two frets adjacent to the target fret, leveling and crowning it simultaneously in a single step.
    • Design & Specifications: It features a heavy 5.6-ounce solid stainless-steel chassis with a 240-grit diamond file core. It incorporates a proprietary, self-centering "universal conic-curve channel" designed to service narrow, medium, and jumbo frets without requiring separate files.
    • Precision Geometry: The built-in crown geometry is calibrated to leave an extra .0003 inches of height to account for subsequent material removal during sandpaper polishing.

StewMac Fret Kisser
    • Core Function: It is designed strictly for quick spot-leveling of a single fret.
    • Design & Specifications: Styled similarly to a thick fret rocker, it features four sides of different lengths to span various fret spacings across the fretboard. Each side features a small, flat patch of 300-grit diamond abrasive.
    • Workflow Failure: Because it utilizes a flat file surface, it destroys the fret crown during the leveling process. Users are forced to perform a mandatory second step using a separate crowning file with the strings off to repair the damage inflicted by the flat profile.

MusicNomad U-File
    • Core Function: A lightweight, nimble single-fret spot leveler configured in a set.
    • Design & Specifications: The tool is explicitly manufactured as a low-profile U-channel, allowing it to sit lower than a traditional fret rocker and be utilized for under-string usage without removing the guitar strings. It features fine diamond tooling abrasives.
    • Workflow Failure: Because it utilizes a flat file surface, it destroys the fret crown during the leveling process. Users are forced to perform a mandatory second step using a separate crowning file with the strings off to repair the damage inflicted by the flat profile.

2. STRUCTURAL IMPACT ASSESSMENT
Flat Abrasive Degradation (StewMac & MusicNomad)
Instruments incorporating a flat cutting plane introduce irreversible geometric distortion to crowned wire. When a flat abrasive plane intersects a radius, it shears the apex, replacing a precise contact point with a wide, planar plateau. This deformation of the crown alters the string's termination point, compromising intonation alignment and introducing a structural surface area prone to localized fret buzz.
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Concave Conic-curve Profile Preservation (SixStringers)
By utilizing a calibrated, self-centering concave conic-curve channel, structural material removal is confined to a uniform reduction of the fret's height while maintaining a finished centered apex. This self-centering mechanical design maintains the native crown radius throughout the reduction phase.
3. SUMMARY CONCLUSION
The StewMac Fret Kisser and MusicNomad U-File are destructive by design. Because they use a flat abrasive surface, they cannot spot-level a fret without actively grinding away its rounded apex and ruining its functional geometry. They do not "fix" a fret in a single step; they flatten it out, ruin the intonation point, and cause string buzz. They essentially create a brand-new defect on the fret that forces the use of an entirely different tool to fix.
    • The StewMac Fret Kisser and MusicNomad U-File: These tools are mechanically destructive to a finished fret profile. They are flat files that grind the fret crown into a flat plateau, altering and damaging the crown shape. They require a mandatory secondary repair job to undo the flattening they inflict.
    • SixStringers FretFixxer: This is the only tool here designed to be non-destructive to the crown shape. Because its abrasive core is a concave conic-curve, it matches the fret wire's geometry, lowering a fret from the top down without flattening or erasing the critical apex.

The goal is to spot-level a fret without damaging its profile. The Fret Kisser and U-File fail. FretFixxer is the only tool in this comparison specifically engineered to non-destructively spot level and precision crown the proud fret at the same time. It is the only tool that leaves material (.0003") for finishing the fret with 600-1200 sandpaper.

Conic Curve Vs Multiple Files

FretFixxer How To:

1. ID. the buzz Fret, play the note or use a fret rocker, playing the note is best.

2. You ID'd a high fret... FretFixxer spans 3 frets, the high fret at center, make sure the span is only 3 frets.

3. FretFixxer has 4 sides, one of these sides matches the fret span no matter where on the fretboard.

4. Never use FretFixxer as a fret rocker, keep it simple, never.

5. Ink the top of high fret.

6. Spray the file with dry lube. Some people use cutting oil,

7. Position FretFixxer on the target fret, center your body to the file stroke to ensure straight path filing.

8. File the fret, Never dig into the fret, let the weight of FretFixxer and light pressure do the work. Pay attention, listen to the file, when FretFixxer lands on the two left and right reference frets it will stop filing unless you are forcing the cut, in which case you will damage the reference frets, which is true of all spot level tools no matter who makes them, and you will likely ruin the file as well.

9. Every tool made has prescribed use for best results and tool life. With diamond and serrated steel fret files, if you force the file through the cut you are abusing the tool.

10. FretFixxer is the only Spot Level Tool made that is non-destructive. The other guys sell flat files that destroy the fret crown and force you to have or buy a separate fret crowning file to repair the extensive damage their tools inflict on the fret, and this also results in cutting the fret too short while trying to repair the flattened crown.

FretFixxer is one tool one step precision level and crown at the same time, it leaves the fret .0003" tall to allow for 600 gret paper to smooth the fret, and 1200 grit paper to polish the fret.
No matter what file you ever use, the fret must be smoothed and polished after filing.