Precision in dressing files – How precise is precise and why?

 

Our precision levelling files are specially manufactured for use in guitar making and are individually tested.

Nevertheless, customers occasionally have questions about the "flatness" of the file and believe that this is the reason for unsatisfactory levveling results – often after testing with a straightedge or a metal surface.

Here we would like to explain some important points to consider and to avoid misunderstandings.

Each levelling file is individually tested for flatness – especially carefully with models for guitar making.

 

Our testing criteria:

• A file is defective if the deviation over a length of 200 mm is more than 0.12 mm (measured with a precision straightedge and feeler gauge).
• Most files have a deviation of 0.05 mm or less.

Therefore, if in doubt, please measure using a suitable method and document the results (photo or video). This is the only way to objectively assess whether a tool is out of tolerance.

 

Why a perfectly straight file isn't necessary!

Files are hardened tools – manufacturing them with this level of precision requires considerable experience.

But even perfect flatness doesn't automatically mean a better result in guitar making.

The reason: A fingerboard – and therefore the fret surfaces – are never completely straight.

 

Based on theoretical calculations and practical experience, after straightening, a slightly curved line results under each individual string, the lowest point of which is around the 15th-17th fret, depending on the scale length, string gauge, and instrument type.

This "groove" is typically about 0.8–1 mm. This geometry is necessary for optimal playability and was deliberately designed this way. Each string has a slightly different curvature, which means that a straight line can't be created lengthwise or crosswise.

You often see in instructions that the fretboard is straightened completely flat with the truss rod before truing, and after re-stringing the truss rod is setup by a certain value of clearance. The assumption is that the string tension and a slight slackening of the truss rod will then create the optimal curve described above.

 

But unfortunately, that's not the case!

 

Very often, a so-called "hump" occurs – a bump where the neck meets the body (on St-style guitars, this is often between the 11th and 13th frets), and if you then file the "fall-off," it fits.

Do you notice anything? Yes, exactly - your dissatisfaction with the dressing result could very probably be caused not by the file, but by the process!

Please keep in mind that a curved fretboard is a three-dimensional cylinder – possibly even a truncated cone if the radius changes along its length.

In addition, you change the radius to small, straight segments with a file (however straight) across the fingerboard and thus change the fingerboard radius.
Do you check the radius while working? How? And how accurately?

These considerations mean that the precision requirements for a dressing file are quality factors to be taken seriously, but are not the only ones that count. In practice, it may be better to use 125mm or 250mm long sanding blocks that match the fretboard radius and sanding cloth glued underneath to dress the top edges of the frets instead of using files that are “as precise as possible”.

 

Typical Misunderstandings During Testing

• "Clattering" on a flat surface does not automatically mean that the file is unusable.
• A small gap between the file and the test surface is normal and within tolerances.
• The decisive factor is not the impression of "it is clattering when rocking," but a specific measurement.

Even in guitar making itself, the flatness of a fretboard or frets is not measured to hundredths of a millimeter – this is simply neither necessary nor practical.

 

The right tool for the right purpose

For a radiused fretboard, we recommend radius sanding blocks (125 mm or 250 mm long) with matching sanding cloth to precisely follow the fretboard curvature.

Levelling files, on the other hand, are particularly useful for rough preparatory work or repairs when it comes to specifically smoothing out unevenness.

Our precision levelling files meet high quality standards that are more than sufficient for guitar making. A perceived "unevenness" is often not a defect, but rather a normal and non-critical manufacturing tolerance – and in most cases has no negative impact on the work result.

If in doubt, please check your tools using a precise measuring method and contact us at any time with any questions.

We are happy to help.

 

If you still do not want to use our files, contact us, and we will find a solution. Because: We want you to be satisfied with our tools and achieve the best possible results.

Returns and Exchanges

• We will, of course, accept returns of unused tools if you are not satisfied with them.
• We will repair manufacturing defects or transport damage with a free exchange.
• Return shipping costs: In the event of cancellation or dissatisfaction, the buyer bears the return shipping costs. If the complaint is justified, we will, of course, cover these costs.