Stainless steel, aluminum and other metal products come with finishes that need occasional buffing. Not only does polishing enhance the quality and longevity of the product but they also rid of the scratches, nicks and more. Additionally, you get to attain the bright, reflective metal most users look for in a finished product.
Different products are used to polish metal surfaces. The most common is the sandpaper which is often used to polish soft metal surfaces or those that need light buffing. For heavy-duty polishing, you want to look for a bench grinder. It is fitted with a buffing wheel which provides faster, more effective polishing.
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We look at how to polish metal using a bench grinder:
Prep the Material for Polishing
There are different ways to prep the metal before polishing it on a bench grinder:
Sanding
Sanding does not make the surface shinier but it save the time required to buff the metal on a bench grinder. Wet sanding is particularly effective when sanding flat surfaces or working on aluminum metals.
Begin by assessing the scratches or casting lines to determine the grit to use. If the metal surface has deep scratch lines use a 320-grit sandpaper. Begin with courser grit and work your way up to 2000 grit making 200-grit increments.
Use a die grinder
Die grinders are ideal when working with a range of sanding attachments including mounted flap wheels, roll-on surface prep discs and sanding discs. This wide assortment allows you to find the abrasiveness required to work on the workpiece.
Choose the Wheel and the Polishing Compound
You need to choose the correct buff or wheel to achieve the desired outcome. There are different types of wheels for the different metals that need polishing. For example, sisal wheels are ideal for aggressive cutting.
They are fitted with a coarse rope-like fiber that frays out to make the brush. The fibers work on the scratches leaving them smooth. Sisal wheels are used with a course emery compound to hasten the removal of the scratches.
Another type of wheel is the spiral-sewn or full-sewn wheel ideal for buffing steel and stainless steel materials. It is used with aggressive cutting compounds like the grey cutting compound to eliminate light scratches and other surface imperfections.
Cushion-sewn wheel and a white compound are best used on ferrous and non-ferrous metals. The combination produces a near mirror finish and will also work on other metal surfaces like aluminum, copper, stainless steel, and brass.
Apply the Polishing Compound
Compounds contain a mixture of fine abrasive fillers and greasy wax. The compound is melted using friction heat and the bar pressed on the rotating wheel. You need to press the compound against the bottom of the wheel as the buffing wheel turns towards you. Avoid overloading the wheel and remove excess compound using a buffing rake.
Polishing the Metal Surface
Once the wheel is coated with the compound you can start buffing. Here are steps to guide you:
- Ensure you are holding the workpiece firmly and move it to the edge of the wheel in a downward angle
- Keep the workpiece should be in constant motion
- Avoid applying too much pressure. Instead allow the compound and the wheel to work on the surface
- You need to reapply the compound as it wears off as you buff
- Once you are done, seal surface with metal lacquer or a coat of wax
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Choosing the Right Buffing Motion
There are two buffing motions:
- The cut motion: This kind delivers a smooth, semi-bright surface. When using this method ensure the workpiece moves against the direction of the wheel and apply medium to hard pressure
- The color motion: The technique delivers a bright, shiny and clean surface. Move the workpiece toward the direction of the wheel applying medium to light pressure
Choosing the Right Buffing Speed and Pressure
You need to apply the right pressure to achieve the best finish while keeping safe. Inadequate pressure does not produce any buffing action while excess pressre causes the buffing wheel to slow down and develops burn marks on the workpiece. For speed you need to maintain a speed of 3600-7500 surface feet per minute. Higher speed delivers fast and better results.
