3+3: Best Practices and Abrasive Options for Grinding/Surface Finishing

July 1, 2018

While it may seem faster and more convenient to use the handiest tool for a grinding and finishing application, here is a word of advice: don’t. Instead, take time to follow the best practices and abrasive options presented here. Remember, the wrong tool can damage the workpiece, lead to costly rework and reduce product life.

Three Best Practices

Using the wrong product or grit size for grinding/finishing application are common mistakes. Selecting the best product for the material type and thickness, and the desired surface finish, can positively impact productivity, costs and the end results.
Here are three ways to save time and money, while achieving ideal grinding/finishing results:

1) Set sights on desired outcomes when evaluating products for a grinding and finishing application. Consider closely the workpiece material type and thickness, operating conditions and surface-finish requirements.

2) Consider material thickness and finish requirements when selecting grit size. For example, coarse, aggressive grits when used on thinner materials can damage the workpiece or remove too much material.

3) Ensure proper use of the abrasive product by following the recommended approach angle to the workpiece. An improper angle can affect performance and product wear, resulting in downtime for product changeover or rework. Training helps operators become familiar with the best practices for each product.

After considering these common best practices, get to know some of the lesser-known abrasive products that can provide benefits given the right application.

Three Abrasive Options

The following provide good alternatives for grinding and finishing, especially on thinner materials:

1) Circular flared-end brushes used on a die grinder can replace manual finishing work in some applications, especially on aluminum. Due to their round shapes, these products provide the same point of contact to the workpiece no matter the angle of approach, allowing operators to manipulate their access angle while still maintaining the same point of contact to the workpiece for a consistent finish in significantly less time than manual finishing. When finishing parts by hand, operators may avoid changing hand positions or tool orientations to work around obstacles for fear of damaging the part.

A smoky haze often lingers on an aluminum part after gas-metal-arc welding. Using a circular flared-end brush in a fine stainless-steel filament, such as 0.006- or 0.008-in. wire, will remove the haze and leave a nice finish. Thinner-gauge wire brushes, well suited for cleaning and finishing thinner material, also are available in larger sizes such as 0.020-in. wire.

As with any wire brush, let the wire tips do the work. Applying too much pressure causes the wires to bend, and can lead to wire breakage and premature brush wear. If the brush requires replacement, consider one with a coarser wire or a different brush-trim length. Brushes with a shorter trim length provide a greater ability to remove aggressive materials, while longer trim lengths can improve operator comfort and perform better on irregular surfaces.

Circular-flared-end brushes allow operators to manipulate access angles while maintaining the same point of contact to the workpiece, for a consistent finish in significantly less time than with manual finishing.

2) Mini flap discs, which provide the same benefits as standard flap discs, are ideal for reaching into tight spaces due to their smaller size–2- and 3-in.-dia., with grit sizes ranging from 36 to 120. While a good option for grinding, blending, deburring, chamfering, edge chamfering and finishing on mild or stainless steel, these discs aren’t an efficient option for working on large surface areas due to their size.

In some applications, mini flap discs can replace small blending discs, as these discs shed cloth and expose new grains to deliver a consistent and aggressive cut rate. They can remove as much as three times the material over the life of the disc as compared to a blending disc. These features save time and money by minimizing product changeover.

Angle and pressure are key considerations when using a mini flap disc. The Type 27 flap disc, well suited for finishing applications requiring lighter pressure and lower grinding angles ranging from 5 to 15 deg., features a flatter profile. For more aggressive, higher-angle grinding, between 15 and 35 deg., try a Type 29 flap disc with an angled design. When using a mini flap disc, avoid placing too much pressure on the disc, and always use lighter pressure when surface finish is a priority. A noticeable drop in sound coming from the tool indicates that the operator likely is using too much pressure.

When using mini flap discs, avoid dwelling too long in one spot. Keep the product moving to avoid gouging or damaging the workpiece. Dwelling also causes heat to build more quickly, which can adversely affect the finish, weld strength and mechanical properties, especially on thinner materials.

3) A 1-mm cutoff wheel, often a better option than a standard 0.045-in.-dia. wheel when working with thin-gauge materials, reduces surface contact with the workpiece to minimize burr formation as well as heat buildup and discoloration throughout the cut.

Especially on thinner materials, friction and heat are the enemies, and imperfections on the workpiece become more obvious. Using a standard-sized cutting wheel on thin materials can result in heat discoloration and burrs down the cut line, which requires secondary operations for cleanup before the process can continue. With a 1-mm cutoff wheel, that extra time and money spent on secondary cleanup can be minimized or eliminated.

On sheetmetal, thin-wall tubing, small rods and similar materials, 1-mm cutoff wheels provide a precise, fast cut. Because of the thinness of the wheel, these products aren’t well suited to cutting thick materials.

Proper technique also helps minimize heat and friction when using a 1-mm cutoff wheel. Just as with other abrasive products, using too much pressure is a common misstep. Use light pressure and consistent movement for a cleaner cut and extended wheel life. Also, avoid dwelling in one spot too long to minimize heat buildup.

Finally, with so many options available for cutting, grinding and finishing applications, consult a distributor or product manufacturer to maximize results. MF

Industry-Related Terms: Stainless Steel, Surface, Abrasive, Burr, Die, Discoloration, Edge, Grinding, Grit, Point, Thickness
View Glossary of Metalforming Terms

Technologies: Finishing


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