What is the difference between linishing and grinding?

You hear machinists talk about linishing, grinding, and polishing. To you, they all sound like ways to smooth out metal, but using the wrong process can leave you with a poorly shaped or scratched workpiece.

Grinding is a broad term for using an abrasive to remove material. Linishing is a specific type of grinding that uses a flexible abrasive belt, also known as a belt grinder, instead of a solid grinding wheel to shape or finish a surface.

In our factory, we produce both rigid grinding¹ wheels and the sanding belts² used for linishing. Both processes remove material, but they do it in different ways and produce different results. Think of grinding with a wheel as a very rigid, precise process, perfect for creating flat surfaces or sharp tool edges. Linishing, with its flexible belt, is better for smoothly blending contours, removing welds on curved surfaces, and achieving a uniform satin finish over a large area. They are two different tools for two different jobs, even though they both fall under the general family of "grinding."

What is the difference between grinding and polishing?

You’ve just ground a weld flat, but the surface is dull and covered in scratches. You want it to be shiny, but when you try to use the grinder again, it just makes more scratches.

Grinding is an abrasive machining process that changes a workpiece’s shape and dimensions by removing material. Polishing is a finishing process that uses a much finer abrasive to create a smooth, reflective surface without significantly changing its size.

This is the most important distinction we explain to our new clients. Grinding is about function; polishing³ is about appearance. When we manufacture a grinding wheel with a 36-grit abrasive, its job is to aggressively remove steel. Polishing, however, uses abrasives with grits in the thousands, or even loose compounds on a soft wheel. Its job is not to remove a measurable amount of material but to smooth out the microscopic peaks and valleys left by the grinding process until the surface is flat enough to reflect light, creating a shine. You must always grind first to get the right shape, and then polish to get the desired finish. They are two separate, sequential steps.

Grinding vs. Polishing: A Direct Comparison

Can you polish stainless steel with a grinder?

You have an angle grinder and want to make a stainless steel project shine like a mirror. But you know that a standard grinding disc will just make a mess of the surface.

Yes, you can absolutely use an angle grinder to polish stainless steel, but not with a grinding disc. You must replace the disc with specialized polishing attachments, such as buffing wheels, and use polishing compounds.

An angle grinder is just a motor that spins a disc. Its function is defined by the attachment you put on it. To turn it into a polisher, you first need to equip it with buffing wheels⁴. These can be made of various materials like felt, sisal for aggressive cut-polishing, or soft cotton for a final high-gloss finish. The second part of the equation is the polishing compound. These come in solid bars of different colors, each for a different step. For example, you might use a gray or brown compound for the initial "cutting" stage to remove scratches, followed by a white or blue compound for the final "coloring" stage to bring out a mirror shine. For best results, a variable-speed grinder⁵ is better because high speeds can burn the compound.

Can a bench grinder be used for polishing?

Your bench grinder is great for sharpening tools and de-burring parts. You wonder if this stationary machine can also be adapted to put a mirror finish on smaller items.

A bench grinder is an excellent tool for polishing. The process is simple: you remove one of the grinding wheels and install a polishing mop or buffing wheel in its place. This creates a stationary polishing station a perfect for small parts.

Many of our customers set up their workshops this way. It’s an efficient use of space and equipment. Converting one side of your bench grinder⁶ into a polisher is easy. First, ensure the machine is unplugged. Then, remove the outer guard and undo the arbor nut to take off the grinding¹ wheel. Replace it with a polishing buff of the same diameter, making sure it is securely fastened. You don’t typically use the guard with a soft polishing wheel. To use it, you turn the machine on, let the buff get up to speed, and then gently press a bar of polishing compound against the spinning wheel for a few seconds. This "charges" the wheel with the abrasive. Then you can press your workpiece into the buff to polish it. Always wear safety glasses, as the wheel can sometimes grab a part from your hands.

What is the difference between a grinder and a polisher?

You see dedicated polishers for sale that look very similar to angle grinders. You assume they are interchangeable, but their price and specifications are different, which is confusing.

The main difference is speed (RPM). A grinder is a high-speed tool designed for rapid material removal. A dedicated polisher is a lower-speed tool, often with variable speed control, designed to apply friction and polish without burning the surface.

This is a critical distinction based on the physics of the work. As a tool manufacturer, we design them for their specific purpose. A typical 4.5-inch angle grinder runs at a fixed, high speed of 10,000-12,000 RPM. This is perfect for driving a grinding disc to cut metal. However, this speed is far too high for polishing. It would generate so much friction and heat that it would burn the polishing compound and scorch the surface of your workpiece instantly. A dedicated polisher, on the other hand, operates at much lower speeds, typically between 600 and 3,000 RPM. This lower speed allows the buffing wheel and compound to create a brilliant shine through controlled friction, not destructive heat. While you can polish with a grinder (preferably variable speed), a dedicated polisher will always offer more control and better results.

Conclusion

Grinding shapes material, while polishing only shines the surface. Linishing is a form of grinding that uses a flexible belt. These are all distinct processes that require the correct tools.