Understanding the 3 Types of Abrasives

1. Sanding Screens: The Multi-Surface Abrasive

What are Sanding Screens?

Sanding screens are mesh-like abrasive materials that allow debris and dust to pass through as you work. These screens are typically made of aluminum oxide or silicon carbide grains, bonded to a durable open-weave fabric. The mesh structure makes them effective for sanding soft materials and wet surfaces, minimizing clogging.

Key Advantages:

• Durability: Sanding screens tend to last longer than traditional sanding paper since their open weave prevents clogging, which often shortens the life of other abrasives.
• Clog-Resistant: The design allows dust and debris to pass through the screen, ensuring continuous cutting action.
• Versatility: These screens work well on both wood and drywall, and can be used for wet sanding applications like polishing or refinishing floors.
• Reusability: With proper cleaning, sanding screens can be reused multiple times.

Best Applications:

• Drywall: Sanding screens are ideal for smoothing out joint compound on drywall without gumming up.
• Wood: Useful for sanding hardwood floors and removing old finishes.
• Wet Sanding: Perfect for use with water or other lubricants to create a smoother finish and minimize dust.

2. Aluminum Oxide Discs: The All-Purpose Abrasive

What are Aluminum Oxide Discs?

Aluminum oxide discs are one of the most common abrasives due to their versatility and effectiveness. Made by bonding aluminum oxide grains to a fiber, paper, or film backing, these discs are designed for both wood and metal applications. They come in a range of grits, making them suitable for everything from rough grinding to fine finishing.

Key Advantages:

• Long-Lasting: Aluminum oxide is a tough, durable material that self-sharpens as it wears, extending its lifespan.
• Versatility: Available in various grit sizes, these discs are excellent for a wide range of applications, from removing rust to sanding wood surfaces.
• Affordable: They offer a cost-effective solution for most general sanding tasks.
• Heat Resistance: Aluminum oxide can withstand higher temperatures, making it suitable for heavy-duty sanding and grinding tasks.

Best Applications:

• Metalwork: Aluminum oxide discs are excellent for removing rust, polishing metal, or prepping surfaces for welding.
• Woodworking: Ideal for sanding down hardwoods or prepping wood for finishing.
• Paint Removal: Useful for removing old paint, varnish, or lacquer without damaging the surface beneath.

3. Net Abrasives: Dust-Free Sanding

What are Net Abrasives?

Net abrasives are relatively new compared to traditional sanding materials. These abrasives are designed with a grid or net-like structure, similar to sanding screens, but with a finer mesh that maximizes dust extraction. The abrasive grains are bonded to the net backing, ensuring a smooth finish while efficiently removing material.

Key Advantages:

• Superior Dust Extraction: The open structure allows dust to be vacuumed up almost entirely, creating a cleaner workspace and a healthier environment.
• Smooth Finishing: Net abrasives provide even surface contact, which reduces the chance of scratches or imperfections in the material.
• Extended Lifespan: Because they don’t clog as easily, net abrasives can be used longer before needing to be replaced.
• Cleaner Work Environment: By minimizing airborne dust, net abrasives help maintain a cleaner workspace, which is especially important in fine sanding or sensitive environments like automotive or cabinetry.

Best Applications:

• Finishing Work: Net abrasives are perfect for achieving fine, smooth finishes on wood, metal, and other surfaces.
• Automotive Industry: Commonly used in car body shops where dust control is a major concern.
• Detail Sanding: Ideal for intricate work that requires precision and a clean finish, such as sanding between coats of finish or working on soft materials.

Understanding Grit

Grit is a measure of the size of the abrasive particles embedded in sandpaper, discs, or other abrasives. The lower the grit number, the coarser the abrasive, which means it can remove material quickly. Higher grit numbers indicate finer particles that result in smoother finishes but remove less material. For example, a 40-grit abrasive is coarse and aggressive, suitable for removing thick layers of material, while a 400-grit abrasive is fine, providing a smooth finish with minimal material removal.

The Grit Scale Explained

The grit scale is standardized by organizations like the Federation of European Producers of Abrasives (FEPA) and the Coated Abrasive Manufacturers Institute (CAMI), which categorize abrasive products into coarse, medium, fine, and extra-fine.

• Coarse (40-60 grit): Best for heavy material removal. Coarse grits are ideal for stripping paint, leveling rough surfaces, and shaping materials like wood or metal.
• Medium (80-120 grit): Used for preparing surfaces for finishing by smoothing out rough spots, removing surface imperfections, and leveling.
• Fine (150-220 grit): Typically used for final sanding before applying paint, stain, or finish. These grits provide a smooth surface without over-sanding.
• Extra-Fine (240+ grit): Reserved for fine polishing or sanding between coats of finish. They create an ultra-smooth surface with minimal material removal.

How Grit Affects Surface Finish

The size of the grit affects not only how much material is removed but also the quality of the surface finish. A coarse grit will leave deep scratches, while finer grits leave a smoother finish with more subtle scratches. Here's how different grit levels affect surfaces:

• Low Grits (40-60): These grits are used when aggressive material removal is needed, such as stripping old finishes or quickly shaping surfaces. However, they leave visible scratches and require follow-up sanding with higher grits.

• Mid-Range Grits (80-120): These are perfect for refining surfaces after using coarse grit. They remove deeper scratches left by lower grits and start to smooth out the surface for a finer finish.

• High Grits (150-240+): When you need a very smooth surface, high-grit abrasives are the way to go. They are ideal for final sanding before applying a finish, or for sanding between coats of paint or varnish to create an ultra-smooth final result.

Matching Grit to Your Project

Choosing the right grit depends on the material you're working with and the stage of the project. Here’s a general guide:

1. Rough Shaping & Stock Removal (40-60 Grit):

   • Woodwork: Coarse grits like 40 or 60 are great for removing excess wood or shaping edges quickly. Made for quick removal of a lot of material and can be used as a first pass before refining the surface with finer grits
   • Metalwork: When working with metal, such as grinding welds or removing rust, use low-grit abrasives for aggressive material removal.

2. Surface Preparation (80-120 Grit):

   • After rough shaping, move to a medium grit (80-120) to smooth out the surface, especially in woodworking or automotive bodywork.
   • Medium grits are also used for general sanding tasks like roughing up walls for primer or painting, and quickly prepping drywall joint surfaces for a final pass with finer grits.

3. Finishing (150-240+ Grit):

   • For final sanding before painting or staining, use a fine grit (150-220) to create a smooth, ready-to-finish surface.
   • For sanding between coats of finish or for polishing, use extra-fine grits (240+) to refine the surface without removing much material.

When to Progress Through Grits

In most cases, you’ll need to work through multiple grit levels to achieve the best finish. Here’s how to progress through grits:

• Start with coarse grit: Use 40-60 grit for rough shaping or removing tough material like paint or rust.
• Move to medium grit: After the initial pass, switch to 80-120 grit to refine the surface and reduce visible scratches. For most painting and drywall joint prep these are the grits you start with.
• Finish with fine grit: Use 150-240 grit for final sanding before finishing, or for polishing between coats of paint or varnish.

Skipping grits can result in an uneven surface and visible scratches that will show up in the final finish. Always move progressively through the grit levels to ensure a smooth, consistent result.