It’s challenging to meet metal fabrication goals without selecting the right abrasive. Numerous factors will combine to determine which ones to use. However, the tips here provide some useful insight for achieving the desired outcomes and avoiding pitfalls.
Understand How Some Abrasives and Methods Could Affect the Material
An excellent starting point is to verify how different abrasive types and ways of using them could prove inappropriate for the base material. For example, the heat buildup of a grinding wheel could discolor stainless steel. That’s not a problem if the part will eventually get painted, but it could become an issue otherwise.
Another fact to keep in mind about stainless steel is that surface contaminants can harm its protective oxide film. If that happens, corrosion can begin immediately afterward. That’s why some fabricators use rotary brushes rather than grinding discs when removing coatings or rust from the material.
Brushes are comparatively not as prone to getting blocked with particles that could hurt stainless steel. People involved with fabrication must also stay aware of stainless steel cross-contamination risks. For example, once someone uses a wire brush on carbon steel, the best practice is to keep it away from stainless steel.
A heat-producing abrasive method could also harm aluminum due to its low melting point. More specifically, the warmth could cause the metal to stick to the abrasive, eventually becoming so severe that the accumulated material becomes higher than the cutting grain. In such cases, the abrasive can no longer perform as intended .
Knowing about any potential complications that could occur when using specific abrasive measures on particular metals will help fabricators increase their success rates. Moreover, such knowledge could cut costs associated with unintended consequences during finishing.
Weigh Cost Considerations With Average Lifespans
A metalworking project’s budget can also influence a person’s abrasive choice. However, an individual should try not to get too caught up in upfront cost as a deciding factor.
For example, a grinding wheel more appropriate for a frugal budget may also have a shorter lifespan. In such cases, it often makes more financial sense to spend more money and enjoy the ability to use an abrasive tool throughout a longer period.
For example, ceramic-grain abrasives may have twice the upfront costs of other options. However, they typically last twice as long.
Another valuable consideration is how ongoing wear affects an abrasive’s performance. Zirconium and ceramic grains fracture and continue removing material quickly even as they wear. However, an aluminum-oxide grain provides a fast cutting speed at the beginning of its life that declines with use .
Another aspect that can influence the cost and lifespan of an abrasive is whether the user discards it at the appropriate time. Some people don’t realize that they can use a grinding wheel until the center of it becomes worn.
Also, a flap disc will keep functioning well despite looking worn. Users can keep relying on them until they can see the epoxy or adhesive through the abrasive’s flaps.
Consider How Different Abrasives Affect Painting Prep
When people work on metal fabrication projects that will include painted surfaces, it’s especially necessary to show forethought. That’s because using the abrasive to achieve an even scratch pattern on the surface will help the material hold the paint, particularly when the specifications require applying paint until reaching a certain thickness.
However, before people start using an abrasive on the metal in preparation for painting, they should ensure there’s a clean surface. Abrasive blasting is one commonly chosen method of cleaning materials before painting them. Since it involves using inert media, abrasive blasting will not cause a chemical reaction with the targeted metal surface. After getting the surface sufficiently clean, those working with the material should anticipate needing to use several abrasives at different stages .
Evaluating Which Grit Options Work Best
People often start with a 36-80-grit coarse abrasive to get welds level, smooth out any deep scratches, and eliminate weld spatter. If the material has a high weld or weld spatter, 36-grit abrasive will remove the material efficiently.
However, a 60- or 80-grit abrasive is less aggressive and likely the best choice when the material has prominent weld spatter and height .
Next, using light grinding and blending discs on the metal can minimize the peaks and valleys. The ideal outcome is to have a consistent pattern characterized by a small distance between the peaks and valleys. When the peaks are too deep, they’ll fill with paint and increase the overall time required to cover the surface. However, the paint may flake off when the peaks and valleys are too small.
It’s also essential to consider that using an overly coarse abrasive at the start could prove counterproductive. That’s because when people need a smooth finish, a coarse-grit abrasive could create deep scratches in the metal that take longer to remove during later steps. The alternative is to use finer grits in the first step. Doing that may take longer initially, but it could remove some other steps.
Some fabricators also opt to use orbital sanding discs in their second or third steps when preparing to paint metal. Doing that creates a circular pattern in the metal. However, working with a random orbital grinder next could make that aspect of the surface less noticeable by breaking down its peaks and valleys.
When people work with new abrasives while preparing metal for painting, they should also experiment by using the products on pieces of scrap metal or non-critical parts. Such tests let them gauge the results without dealing with costly unwanted outcomes.
Think About Using Engineered Abrasive Blends
Some metal fabricators may find that engineered abrasives made from blended grains could give them the desired finishes, especially when working with alloys and steels that are not always well suited to precision grinding wheels.
One in-depth investigation involved using seeded-gel (SG) sintering technology to make grain abrasives out of highly pure ceramic aluminum oxide. The SG approach inserts nanoparticle alumina seeds. It makes a heterogeneous structure of 100- to 500-nanometer crystallites. It can become an effective abrasive with a controlled fracture rate .
Engineers involved in this test used grinding wheels made from 100%, 50%, and 30% Targa grain. While the 30% and 50% versions showed similar grinding power consumed in all grinding conditions, the 100% Targa wheel drew 6%-8% higher power during all tests compared to the wheels with higher percentages of other materials. However, the conclusion is that this difference did not create problems for most work surfaces .
The main exception is when people work with materials that have low thermal diffusivity. In such cases, the 100% engineered wheel’s power difference could cause thermal damage, including cracking. Overall, though, the 100% engineered wheel showed consistently high metal removal rates, allowing for increased productivity rates without excessive grinding wheel wear.
As the examples here show, taking the time to thoughtfully choose the abrasives for upcoming metalwork projects can reduce the overall money spent or the effort required to complete the job. Moreover, the properties of certain materials may mean people should consider certain abrasive materials inappropriate from the start.
However, weighing such factors before beginning a project is one of the best ways to help it go smoothly. Additionally, learning what works best for certain materials and projects prevents later errors.
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