There are many ways to get there. Here is my method - Strip the fork and blend out the deepest gouges (10-20 thou) with a flap wheel (Al Oxide) or preferably a die grinder with a scotchbrite wheel/Disc. Start with brown (coarse) and go easy as It will remove material quickly, go with red if the gouges are less tan 10 thou and work down to blue for 5 thou and under. Take off the material surrounding the deepest part of the gouge/scratch to achieve a generous blend ratio usually about 20:1. That means for a 10 thou gouge, the blend width should be approx .200 inch, or until the damage is feathered out to the desired aesthetic standard for the part. You get the picture?
You can achieve the same results manually using various grades of Al Ox wet and dry, files to remove raised metal etc, it is safer if your not confident with air tools, plus it is cheap but will just take a little longer.
The OEM finish on most KYB/SHOWAs is a uniform brushed finish with a radial brush pattern and then clear coated.
To achieve this, I turn the lower on my lathe whilst holding a small hand held pneumatic linisher with a scotchbrite belt fitted against the fork lower turning at low RPM. I start with a blue belt to get a uniform finish over the entire leg including the previously blended damage.
Don't worry, you can get a good result by working manually if you buy a scotchbrite belt designed for a linishing machine and use it like a strap in a see sawing motion. Hold the lower in a soft jawed vice or get a second person to hold the leg whilst you work along the length with the belt (the helper would turn the leg slowly as you go).
At this point it will be obvious if there are any more areas which require rework to achieve a uniform finish, so repeat the blending in local spots as required and then repeat the turning.
The areas around the axle boss and cable keeper mounts are hand finished with green scotchy, as you cannot travel through this area using the linisher. Carefully work in the same radial direction and avoid cross hatching.
Mask/plug the internal bore to prevent chemical ingress. Clean wipe with solvent such as prepwash, etch with 10% SODIUM HYDROXIDE (mild caustic soda solution) - fresh water rinse - neutralise with acetic acid (vinegar)- fresh water rinse-then dry.
Use POR15 or similar poly clear coat designed to cover bare metal to restore the environmental barrier.
Hints- avoid using silica carbide wet and dry use Al Ox instead as silica carbide can become embedded in the aluminium and a dissimilar metal corrosion attack can result.
POR15 recommends the use of a POR Etcher designed to work with their system and while it is expensive it can save time and the use of the other chemicals I have mentioned.
Avoid using steel wire wheels as they are very aggressive and can leave steel embedded in the soft alloys. Sometimes brass bristled brushes can be handy to remove stubborn soiling.
A highly polished finish can be achieved if you work hard at getting all the scratches and pitting out, otherwise you will only highlight every small defect. Brushing is a little more forgiving and is more like the factory finish.
