DIY: Swiss Army Knife Scale Refinishing

I’ve recently acquired some used Victorinox Swiss Army knives that have seen better days. Beside rusted and dulled blades, the handles – or scales – of some of the knives were in terrible condition upon arrival. The scales of most Victorinox knives are composed of a material called cellidor, which is a type of plastic resin. Being plastic, the scales respond well to a refinishing process that is popular for the headlamps of vehicles produced around or after the late 1990s. These vehicles have sealed headlamps with a clear plastic cover that gets pitted from prolonged exposure to road debris, rendering them cloudy and hazy. The refinishing process adapts well to Victorinox handles because the materials are readily available at most auto parts stores, and may likely already be in one’s garage, thus making the refinishing economically viable. Unless the knives are to be part of a collection and not used on a frequent basis, the refinishing procedure – as a matter of prudence – should not exceed the value of the knife. After gathering materials, the refinishing process should take about 20 minutes per side.

The process takes headlamps that look like this…:

…and makes them look like this:

You Will Need:• To be sober• 320 grit (~P400) wet/dry sandpaper• 400 grit (~P800) wet/dry sandpaper• 800 grit (~P1500) wet/dry sandpaper• 1500 grit (~P2500) wet/dry sandpaper• 2000 (~P3000) grit wet/dry sandpaper• Rubbing compound (3M Rubbing Compound or equivalent)• Plastic polish (Meguiar’s PlastX or equivalent)• Painter’s masking tape or equivalent low-tack tape• Microfiber towel• Container for water

Note that the grits of sandpaper are not absolute – they are only what I had on hand at the time. The lowest, coarsest grit should be around 400 and the highest, least aggressive grit should be around 2000. The maximum grit is dependent on the rubbing compound and polish that is chosen. Increasing sandpaper grits removes the relatively coarser scratches left by the lower grits, and subsequently the rubbing compound removes the finer scratches from the sandpaper with the highest grit. Therefore, the highest grit sandpaper should not exceed the scratch-removal rating of the rubbing compound. In the gradations of grit between the extremes, there is more leeway. While the progressions in grit were sufficient, an iteration with 1000-grit sandpaper in between the 800-grit and 1500-grit would have noticeably expedited the process.

Survey the Damage:Below is a small collection of Victorinox and imitation Victorinockoff Swiss Army Knives, all used and well worn. The yellow and blue Victorinox Classics that are circled in red will serve as examples for the refinishing process. Note the extreme maladies in the blue model:

A Yellow Victorinox Classic shows typical signs of advanced wear: scratches and pits filled in with dust and debris. Increasing the contrast of the photograph allows the deficiencies to be highlighted:

The blue Victorinox Classic shows deep pits and is beyond typical damage:

Prepare the knife by taking out the toothpick and tweezers from the scales and gently remove any loose dirt from between the blades/tools and body using a soft brush or compressed air. Mask off those portions of the knife which warrant protection. Typically this would be the steel blades/tools but for this example half of the entire knife will be taped:

A close-up shows the extent of the damage to this particular knife. Note that although the cellidor scales are gnarled and scratched in places, they still retain a shine:

The initial scouring with a low-grit sandpaper will remove the bulk of the surface deficiencies. Though drastic in appearance, the depth of harsh pitting on the scales is on the order of thousandths of an inch and should disappear quickly. A secondary result of the sanding is the removal of third party logos from the scales. Though this is usually a welcome occurrence, logos that are to remain in place should be masked off. Note that while most third party logos are simply printed onto the knife, the Victorinox logo is a small metal planchet embedded into the scales, and cannot be removed by the simple sanding of this refinishing process.

Sanding:Begin by wetting the lowest grit sandpaper. In this procedure, copious water is not necessary. Thus, the sandpaper may be dipped in lieu of being soaked, although soaking will maintain wetness longer:

Hold the knife down on a work surface with one hand and hold the sandpaper with the other. Alternatively, the knife can be clamped such that the entirety of the portion to be sanded is exposed. Move the sandpaper across the knife, wet sanding the exposed portions of the scales in one direction only, and applying an even downward pressure onto the knife. Do not hold the sandpaper stationary and move the knife across it. Maximum coverage of the scales should be achieved in each stroke, i.e. don’t concentrate on one area but rather the entire swath of the scale. At either end of each stroke, allow your fingers and the sandpaper to lightly drape over the filleted edges of the scales. This will allow the rounded edges of the scales to receive treatment. Holding the sandpaper stationary and moving the knife does not allow for the round edges to be sanded. For the same reason – unless explicit care is taken to treat the edges – do not use sanding blocks, belt sanders, rotary devices, etc. These devices may remove excess material from the scales and not enough from the sides, resulting in a hard chamfered edge.

The sandpaper has an initial frictional grip which should be noted. This friction is due to the microscopic grains of the abrasives scraping across the cellidor. As more material is removed, the fine dust that is created is embedded between the abrasives, clogging the sandpaper and making it less effective. This occurrence can be discerned by a noticeable lack in friction between the sandpaper and the scales. When this occurs, move to a new section of sandpaper or clean the sandpaper with water.

After a brief period of sanding, most of the imperfections will have been removed. If needed, continue with the lowest grit until any logos begin to wear away. Note that in the following photograph, the portion of the logo closest to the center of the scales is being removed more quickly than those portions

toward the edges. This is due to the natural tendency of the fingers to seek the most stable portion of the scales to avoid slipping off of the knife during sanding. Care must be taken to sand the entire area evenly such that a depression in the center of the scales (however slight) does not form:

Once all of the surface scarring is gone and any logos have been removed, the low-grit sanding step is complete. At this point the scales should have lost their shine and appear to have a dull, matte finish:

Begin sanding with the next increase in grit, this time in a direction perpendicular to the initial sanding. Again, allow your fingers and the sandpaper to drape over the edges to treat the fillets of the scales, and monitor the decrease in friction as the sandpaper becomes clogged. Move to a new section of sandpaper or clean it with water if this occurs. Continue until all of the lines from the previous grit of sandpaper are gone. This can be discerned visually: if there are etchings or lines in a direction orthogonal to the current direction of sanding, then they are from the previous grit and treatment needs to be prolonged until they are ground away. Periodically, clean the cellidor dust from the scales and hold the knife close to a bright light such that all striations or grooves can be confirmed to be in one uniform direction. When this has been achieved, sanding with the current grit is complete, and sanding with the next gradation can begin.

Continue through the all of the increasing degrees of grit, switching sanding directions each time, noting decreasing friction, and until all etchings are uniform. Ascend grits until the highest has been achieved. After the high-grit iteration, the shine on the cellidor scales should start to return and the surface should be much more smooth and uniform:

Rub One Out:Once the sanding is complete, the striations from the highest grit sandpaper must be removed with rubbing compound, which is nothing more than a fine abrasive powder in a viscous substrate. Apply a small dollop to a microfiber towel. A blob the size of a pea should be more than sufficient for one scale:

Work the rubbing compound into the cellidor with a back-and-forth motion, alternating directions periodically and occasionally circulating in an orbital motion. The rubbing compound does not leave grooves which are macroscopically visible, so the knife should be sanded in many directions. Apply copious pressure to the scales, holding the knife and working the compound in with the thumb of the same hand if needed. Continue rubbing until the towel can be felt sticking to the scale; there should be no need to apply more rubbing compound or to switch to another portion of the cloth. Periodically remove the microfiber towel and fluff the pile (individual woven loops) of the fabric that should have become matted from the scouring. Rubbing compound is aggressive enough to remove visible amounts of cellidor plastic, as can be evidenced by periodically checking the microfiber towel. When the entire wetted portion of the cloth has been colored by cellidor dust, treatment with rubbing compound is complete, as evidenced by the following photograph:

Note the slight reflection on the top portion of the knife fillet from the angle in the photograph.

Wipe any excess slurry of rubbing compound and cellidor dust from the scale and check it against a bright light. There should be no traces of etchings and the plane of the scale should be smooth and even. There should be no scratches that are either macroscopically visible or detectable by feel, and the scale should have a shine rivaling that of a new knife:

Polishing off:The final step in restoring the scales of a Victorinox knife is polishing, which further increases the shine, deepens and enriches the color of the cellidor, and enhances the smoothness. The application of plastic polish is similar to that of the rubbing compound: apply a small dollop to a microfiber towel and rub into the scales in an orbital fashion using copious pressure. The microfiber should not stick to the scales as much as the rubbing compound, as very little abrasion is taking place; the cloth should glide over the scales and there should be little to no color transfer. Periodically fluff the pile of the cloth and continue rubbing until the scale feels slippery. It is at this point that the restoration of the scales is effectively complete. Move to an unused portion of the microfiber towel and wipe clean any excess polish. The shine of the knife should radiate and reflections be straight and true, with a deep color to the scales:

Note the increased reflection from the top portion of the fillet from the angle in the photograph.

Finish Her Off:Remove the tape from any areas that have been masked off and inspect the grooves of the knife for residue and dust. Clean any crevices with a toothpick and give the knife a final wipe with a clean, damp microfiber towel. The cellidor scales of the knife should look brand new and in excellent condition.

Note that the wet sanding process removes a small layer of the cellidor plastic, so care must be taken to avoid the removal of too much material. Following is photograph of the visible change in level:

After only five gradations in grit, enough material has been removed to cause a visible difference when compared side-by-side with an untreated portion. The amount of material to be removed should be dictated by the deepest scratches in the scales that will be mitigated.

Following is a close-up photograph of the completed cellidor scale:

Two final photographs, showing the extent of the shine and the detail of the visible reflections. Note the lack of pitting on the scales and the crispness of the reflection in the second photograph:

Finally, a Victorinox knife any Mets fan can love!

Caveats:

Albeit the scales respond well and respond quickly to the refinishing process, the same properties of the cellidor scales which allow them to be easily brought back to life also allow them to be easily marred. The scales will become scratched again in a matter of days, especially if the knife is kept on a keychain adjacent to keys or in a toolbox. However, the scratching from everyday use over the course of a few weeks does not impede the shine and the reflective properties of the knife, and is only visible from a close distance under a bright light. The knife will continue to appear shiny and smooth from a casual distance. Dulling of the scales from being scratched daily takes an amount of time on the order of months.

If the knives are to be kept in a collection, unused on a day-to-day bases, then the entire process is recommended. If the knives will be used daily and subject to scratching, then the final step of polishing, or the final two steps of rubbing compound and polishing may be omitted, using discretion. To maintain the shine, periodically treat the scales with the plastic polish and a microfiber towel. If done weekly, polish will suffice; if done bi-weekly or longer, rubbing compound may have to be employed. Begin with the least aggressive treatment (polish) and work backward (rubbing compound, 2000-grit sanding, 1500-grit sanding, etc.) on a test area of the scales in order to find the appropriate starting point. Once any scratches have been satisfactorily removed, continue back up in the opposite direction as per the original directions in this guide.

After refinishing the cellidor scales, clean and sharpen the metal parts of the knife appropriately. Be sure to use copious lotion after handing the cellidor dust as it dries out the skin rather quickly. Like any good DIYer, clean and save those pieces of sand paper. Finally, marvel at a job well done!

April 2009