How to Polish with Sponge Sandpaper?

Sponge sandpaper is made up of sponge and abrasive. It is produced through various processes such as gluing, planting, compounding, and punching. It is suitable for polishing the rough surfaces of materials such as solid wood furniture, metal stainless steel, automobile maintenance, machinery manufacturing, plastic glass, decorative crafts, and so on.

1. What is sponge sandpaper, and what are the categories?

Sponge sandpaper is a strip tool consisting of abrasive bonded to flexible materials such as paper and cloth for grinding and polishing. Sponge sandpaper consists of a substrate, abrasive, and binder. Sponge sandpaper has two kinds of substrates: cloth and paper. The paper-based substrate is a type of sponge sandpaper made from high-strength paper treated in a particular way. The price of paper-based sponge sandpaper is 1/3-2/3 lower than that of cloth-based sponge sandpaper. Paper-based substrates are relatively hard and can polish high-gloss surfaces. Paper-based sponge sandpaper is used in precision grinding and ultra-precision grinding. Cloth-based substrates are stronger than paper-based ones, less sensitive to temperature and humidity, and more durable. The abrasives commonly used in furniture production are aluminum oxide, silicon carbide, alumina-zirconia, garnet, and glass sand for hand sandpaper, each with its characteristics.

Rough grinding, large plasticity, and large grinding area require coarse particles to prevent debris from getting embedded, and the workpiece from being too soft. Fine particles are used for fine grinding of hard workpieces. Abrasives are bonded to the substrate by a binder, which should be strong, elastic, heat-resistant, and water-resistant. Common binders are divided into animal glue and synthetic resin. Animal glue is not water-resistant, while synthetic resin has better water resistance. Water-resistant sponge sandpaper uses water-resistant synthetic resin as the bottom and top glue and undergoes strict waterproof treatment. By combining the substrate, abrasive, and binder, selecting the appropriate substrate, abrasive, and binder according to the processing object and process requirements, sanding requirements can be achieved.

2. Sanding with sponge sandpaper

When using sponge sandpaper to polish the surface of a crankshaft, there is usually an anodized layer. It is tiring and difficult to control the force of sanding with sandpaper, so you can try spraying a strong microwave oven cleaner on the surface. The alkali in the cleaner can react with the anodized layer and remove it. When the surface turns black, it is ready for polishing with sponge sandpaper. 

As for the issue of chamfering, it depends on the feeling in your hand. When grinding to the edge, try to control the angle of the sandpaper. It is best not to use very coarse sandpaper to grind the chamfer, as the shine after polishing is not noticeable. There are no special polishing techniques, only the result of physical effort, sweat, and patience. It is recommended that you wear thin rubber gloves to avoid blisters on your fingers. If conditions permit, you can buy a table angle grinder and install cloth or wool wheels, which also have good effects.