After I got tired of polishing all the paintwork by hand, I thought about building a polishing machine myself. This not only saves a lot of time and elbow grease, but also the surfaces shine professionally ;-)
I show here two possibilities. One is for "polishing once in a while", the other for more frequent use. The latter consists of a 750W/240V motor at 1280 rpm, a 1:2 belt transmission, a double-bearing polishing shaft, and two cotton polishing wheels. The speed can be described as "cozy". Better is double speed and correspondingly more power. Everything together is mounted on a board and equipped with a switch. Of course, the safety regulations must be observed(accident prevention, electrical safety, etc.)! On this polishing stand I use two discs per side. To get into the tight radii on electric guitars, I like to use one disc on the boron machine. One disc in width is also sufficient for very good results. If the disc rotates, it becomes a little wider.
Of course, you could also build the disc yourself and cut it from soft cotton cloth, but it takes a long time - you need about 250 discs - Depending on the thickness of the fabric and the disc of course - not really an alternative.
With the polishing wheels themselves you must absolutely pay attention to quality! Not every polishing wheel is equally good - not even everything that comes from overseas. This is due on the one hand to the choice of material and on the other hand to the design. If you polish stainless steel cutlery or aluminum rims of the motorcycle to a high gloss, you take other materials than the sensitive instrument varnish. Known materials are: Sisal nettle fabric, felt lamellae, molton lamellae, fine nettle, cotton fabric, etc. The material must be seamless, soft and at the same time dynamically react to pressure during polishing. If the fabric is very often folded on the radius, it can carry more polishing paste and the amount of polishing material engaged is also greater. The resulting oscillation unifies the polishing pattern and cooling is also greater. This allows you to stay on one spot longer without "burning out" right away.
In my products you will find professional discs, as they are also used in the very large manufactories (approx. 300mm diameter, 25mm width). Depending on the selected drive type you get them with drill adapter (010130010 + 010130020), 30mm (010130011) or 19mm (3/4") bore (010130010). With an inexpensive adapter set (010130021), bores down to 12mm can also be served.
For hard to reach places (e.g. on electric guitars the horns towards the neck) or for not too frequent use, the combination drill / buffing wheel is also a good choice. In the pictures below I have mounted the 300mm disc on an adapter. The drill itself must be mounted in a stable (!) drill holder. There is often no room for such large discs under normal drill stands, so it is best to mount them horizontally, standing above a workbench.
The device is intended for polishing high gloss lacquers that have been previously sanded with water sandpaper (600,800,1000,1200). Of course, you can also quickly polish a piece of bone saddle, ebony or rosewood with it, but if you want to polish a fretted fingerboard with it, you make the discs so dirty that they are no longer suitable for lacquer polishing, so better buy one separately if you intend to do so.
For commissioning, the discs must be "trimmed". The fact is that after the first run at nominal speed, the centrifugal force will produce an uneven polishing surface. If a U-shaped or crowned surface results, the protruding parts of the stock must be cut off with the scissors at standstill (!). Only when a straight pressure surface is obtained during turning can you start.
Now the fabric must be "opened up". This means that with a special squeegee (01-013-0022 Scratch Polishing Discs), the first 1-2mm are loosened. This is the area that can then absorb polishing paste. To do this, hold the squeegee against the pressure surface for a short time and check the result, repeat if necessary. Then polishing paste is held against the running discs and polishing is started. Depending on the polishing progress, the application of polishing paste is repeated every 2-3 minutes. Hold briefly against the disc, continue polishing, etc.
A widely used and very good polish for instrument varnish is manufactured in Germany by the company Manzerna.
One disc is reserved for pre-polishing (010130001 Polishing Paste Pre-polishing (brown)), the other disc for final polishing (010130003 Polishing Paste Glossy (light beige) and/or 010130005 Polishing Paste Superfine ). On quite inaccessible areas or after touch up I also use 01-013-0007 "Manzerna special polishing cream". After sanding, a little of the polishing cream is applied to a cotton ball and the affected areas are polished to a high gloss with a circular motion.
If you polish the first time ever, you cover the entire workshop floor best with thick foam ;-), because almost everyone has already happened that you polish against the direction of travel, the polishing part eats itself and is flung out of your hand :-).
Before the polishing really starts, you "warm up" the panes with the squeegee or a piece of wood, which you press against the panes in the run. It is best to start with the bottom. First polish the outer areas (around 10cm) and then work your way inwards. As with varnishing, I also move the guitar crosswise. Especially at the edge inlays or inaccessible places in cutaways you have to pay attention to heat development and varnish thickness, check again and again with your hand and eye.
If you have an even, somewhat matte shimmer, you can switch to the final polishing wheel and repeat the process.
If high gloss has been achieved with increasingly careful pressure, small scratches from the polishing discs or from the preparation still like to appear on dark paints. It is then that I use the white superfine polishing compound on the wheel. These small scratches are acceptable and you can see them even on brand new guitars.
Small scratches on used instruments / pickguards can also be removed by spreading and rubbing on a very soft rag or absorbent cotton e.g. 010130007 Manzerna Special Polishing Cream.