Abrasive grit progression are a method that is used to prepare metal for specific processes. Abrasive grit progression requires you to start with coarse grit sizes and work your way to a fine grit sizes. If you dont follow a proper progression of abrasive grit sizes, you will leave deep scratches on the metal that will always be visible once you apply topcoat to the metal.
Each abrasive grit size must work to remove scratches that the previous abrasive grit size made. If the next abrasive grit size are not fine enough to remove the marks made by the previous abrasive grit size, then those marks will remains on the metal. Abrasive grit size are classified by the size of the particles that are on the abrasive sheet.
How to Use Abrasive Grits on Metal
Coarse abrasive grit sizes has large particles on the sheet and are used to remove heavy material from the metal. Coarse abrasive grit sizes are used to remove rust or weld beads from metals. Medium abrasive grit sizes have smaller particles than the coarse abrasive sizes and are used to smooth the metal after the coarse abrasive sizes have removed the heavy material.
Fine and ultra-fine abrasive sizes has the smallest particles on the abrasive sheet. These are used to polish the metal or to prepare metal for painting. These sizes has to be used in the order that they are specified because each size is meant to remove the scratches made by the previous size of abrasive grit.
Depending on the type of metal that you will be treating with abrasive grit sizes, there are different type of abrasive materials that have to be used. For metals that require the removal of heavy material, zirconia grains are some of the most effective abrasive because they are strong and will fracture during use to maintain there sharp edges. For grinding metals like steel, aluminum oxide is one of the most common and more reliable abrasive materials.
For metals like brass and stainless steel, silicon carbide is the preferred abrasive material because it is very hard and can polish those metals effective. For these metals, using the wrong abrasive material will lead to various problems. Using an abrasive that contain iron particles will lead to rust forming on metals like stainless steel.
Abrasive materials can be ground in two different ways depending on the abrasive grit sizes that are used. For coarse abrasive grit sizes, dry grinding method can be used. Dry grinding allows for the rapid removal of metal but produces many dust during the process.
For fine abrasive grit sizes, wet grinding methods are used. Wet grinding methods use water to keep the metal from overheating during the grinding process. The water will also help to wash the small particles that the metal produce during grinding.
If the metal is not washed with water during wet grinding, those small particles will scratch the metal again. Using soapy water or lubricants such as WD-40 during the grinding process will prevent the metal from clogging the abrasive sheet. Depending on the type of metal that is to be ground, there are different methods of grinding that will have to be used.
For metals like aluminum, which are soft metals, the abrasive sheets will readily clog due to the softness of the metal. In these cases, lubricants should be used while grinding aluminum metal. For metals like brass and copper, which are also soft metals, silicon carbide abrasive materials will work best.
These metals may also clog the abrasive sheets quickly so care must be taken when grinding these metals. For any metal grinding process, you should never jump to a grit size that is more than one size larger than the current abrasive grit size. Each abrasive grit size will work to remove the scratches from the previous abrasive size.
Abrasive metals has a rating based on the smoothness of the metals surface. Metals with a coarse abrasive will have a high value of roughness while metals that have been treated with fine abrasive sizes will have a low value of roughness. For metals that require a mirror finish, the metals should be treated with ultra-fine abrasive sizes and wet grinding methods.
For metals that require a brushed finish, medium-fine abrasive sizes should be used. Each abrasive size should be used according to the specification of the required finish for the metal. If the specifications are not met, the metal will have to be ground again.
Finally, you should ensure that the metal tool that are used for grinding metals have the proper RPM ratings for the metal that will be ground. Store any abrasive metal sheets in a flat place in a dry environment to preserve the abrasiveness of the metal.
