Choosing The Right Abrasives For Flawless Finishes
One of the most essential parts of metal finishing is abrasive tooling. If you select the incorrect kind, your customers may not approve of the finish, or you will be stuck with a laborious deburring operation. For this reason, choosing the proper abrasives is crucial when polishing or deburring metal components.
Abrasives are a vital but frequently disregarded component of any machine shop. A few of the problematic outcomes of utilizing an incorrect abrasive are inadequate surface finishes that do not match drawing standards, time-consuming deburring procedures, and improper weld preparation.
TYPES OF METAL ABRASIVE
Metal abrasives are available in a wide variety of shapes, sizes, and compositions, including silicon carbide, ceramic, and aluminum oxide. To assist you in selecting the best abrasive products for your metal finishing activities, let's further dissect these categories:
NON-WOVEN ABRASIVE
Non-woven abrasives provide metal components with a consistent, dependable polish. The ideal complement to larger grits, this comparatively mild abrasive offers a uniform surface that reduces workpiece spreading and discoloration. Sanding strips, hand pads, and flap wheels are typical media types for non-woven abrasives.
Perfect for polishing and finishing workpieces made of copper, titanium, aluminum, and stainless steel.
ALUMINIUM OXIDE ABRASIVES
Aluminum oxide crystals are powerful and reasonably priced. Therefore, aluminum oxide abrasives are among the most popular and efficient methods for finishing and deburring metals. Semi-flexible discs and sanding strips are common media types for aluminum oxide abrasives.
Perfect for finishing and deburring hard metals, such as titanium and steel workpieces.
SILICON CARBIDE ABRASIVE
Although somewhat brittle, silicon carbide is a strong and sharp material. Because of this, this kind of abrasive is most appropriate for finishing tasks requiring little cutting pressure, including graining, to provide a visually consistent finish. Wheels, discs, hand pads, and sanding strips are common media types for silicon carbide abrasives.
Perfect for polishing and graining metal workpieces, including stainless steel.
ZIRCONIA ABRASIVE
Zirconia is an incredibly durable and strong white crystalline oxide. Its abrasives have a high degree of wear and tear resistance, making them ideal for intensive grinding tasks. Discs, sand strips, and discs are common media types for zirconia abrasives.
Perfect for removing slag from the most challenging metals and for heavy grinding and snagging.
SELECT THE APPROPRIATE ABRASIVE GRAIN FOR THE TASK
Each can be classified as either bonded abrasives (wheels, generally), coated abrasives (sandpaper, belts, and discs), or nonwoven abrasives (hand pads, flap wheels, etc.) despite the wide range of shapes, grits, bonding agents, and abrasive media types available. Furthermore, hand-held sprayers and blasting cabinets also use loose media. All of these abrasives function similarly, removing metal from a workpiece with what are effectively sharp, pointy rocks.
The material and shape of the workpiece play a significant role in selecting the right kind of abrasive. Generally speaking, iron needs an abrasive, which is different from aluminum, and vice versa for Inconel. How can you tell if your candidate is the best fit for the job? One factor is the volume of material removed. For example, coarser grades are needed for weld preparation and snagging, while finer grades are necessary for finishing operations. Whichever bond or abrasive type is required may vary according to the nature of the workpiece.
These "rocks" often belong to one of three groups: zirconia alumina, silicon carbide, or aluminum oxide.
GRIT SIZE
Grit Sizes: What We Suggest The term "grit number," sometimes known as "mesh number," describes the range of abrasive mineral particle sizes from 36 to 600 grits. The majority of the sanding products you'll use, though, are in the 60–220 grit range. You don't have to go through the entire grit range when sanding bare wood before finishing, mainly if you use a power sander for part of the task.
We begin by smoothing a flat surface, such as a tabletop, with a sander fitted with an 80—or 100-grit aluminum oxide belt. Then, we move on to a finishing sander with 150—or 180-grit garnet paper. Finally, we use aluminum oxide paper with a granularity of 220.
BE AWARE: ABRASIVES WILL BE WEAR
Over time, abrasives tend to "clog up." The individual grains also become dull and worn out. They quickly lose their effectiveness if no action is taken to reveal new material. This is typically achieved on grinding machines by treating the wheel; however, this is not an option for almost all other abrasives.
The makers of abrasives have worked hard to make their goods "friable" or semi-friable, meaning that when the abrasive becomes dull, it breaks away and exposes a new material. For instance, combining ceramic with aluminum oxide produces a hybrid that is brittle but strong and suited to steels and alloys that are otherwise hard to grind.