Sandpaper Grit Explained, Detailed Guide to Sanding Grit Levels

Achieving a flawless finish on your project’s surface often hinges on the correct sanding technique and selection. Whether you prefer the tactile control of hand sanding or the efficiency of power tools, understanding the different levels of sandpaper grit is essential.

Choosing sandpaper grit is not arbitrary; it's a deliberate choice that dictates the outcome of your sanding process. Each grit level serves a specific purpose, influencing material removal, surface smoothness, and the overall quality of the finish.

Sandpaper grit refers to the measurement of the abrasive particles that are affixed to the surface of sandpaper. This measurement dictates the coarseness of the sandpaper, which in turn determines its suitability for various sanding tasks.

The grit number provides a clear indication of particle size: a lower number signifies larger abrasive particles, while a higher number indicates finer ones. A lower grit number is ideal for tasks like stripping paint or shaping rough surfaces. On the other hand, a higher grit sandpaper is designed to gently smooth and refine surfaces by removing minute amounts of material for a polished finish.

This versatility makes sandpaper indispensable across diverse applications:

• Woodworking: Shapes timber and refines furniture.
• Metalworking: Removes rust and prepares surfaces for finishing.
• Auto-body Repair: Smooth imperfections for flawless paint jobs.
• Home DIY Projects: Fundamental for tasks like refinishing furniture or sanding walls

Sandpaper grading systems categorise abrasives from coarse to fine, providing a clear indication of their material removal capabilities and surface finishing potential. A standard sandpaper assortment usually features 60, 100, 220, and 400 grits, which cover coarse, medium, fine, and super fine sanding needs.

Meanwhile, the rating system is numerical, with lower numbers representing coarser grits and higher numbers indicating finer grits. It's important to note that two primary rating systems are used globally:

• Federation of European Producers of Abrasives (FEPA): This rating system is widely used in Europe and uses the "P" prefix (e.g., P80, P120).
• Coated Abrasives Manufacturers Institute (CAMI): A grit system prevalent in North America and uses numerical values without a prefix (e.g., 80, 120).

Both the highest and lowest grit of sandpaper each serve distinct purposes in achieving specific finishing goals and tackling diverse sanding tasks effectively.

What Is the Lowest Grit Sandpaper?

The lowest grit of sandpaper, typically ranging from 12 to 36 grit, is designed for aggressive material removal. These extremely coarse grits feature large, robust abrasive particles that can quickly strip away thick layers of paint, rust, or other coatings.

Due to their aggressive nature, the lowest grit sandpaper leaves deep scratches on the surface. Therefore, it's essential to follow up with progressively finer grits to smooth out these imperfections and achieve the desired finish. This type of sandpaper is often used with power tools like belt sanders or orbital sanders to maximise efficiency and tackle demanding projects.

What Is the Highest Grit Sandpaper?

On the other hand, the highest grit sandpaper, which can range from 2000 grit and beyond, is used for ultra-fine polishing and achieving a mirror-like finish. These extremely fine grits feature minute abrasive particles that gently refine surfaces, removing microscopic scratches and creating a smooth, polished appearance.

The finest sandpaper grit options are often used in specialised applications such as automotive refinishing, jewellery making, and precision metalworking. They are ideal for wet sanding, which involves using water or lubricant to prevent clogging and achieve an even smoother finish. Ultra-fine grits are also employed for polishing delicate materials like plastics, ceramics, and high-gloss coatings.

The material being sanded and the desired finish dictate the choice of sandpaper grades. And a sandpaper grit chart can help guide your selection, ensuring you choose the appropriate sanding grit for each stage of your project. To help you choose the right grit for various applications, consider this quick guide:

• Wood Sanding: The process typically involves a progression from coarse to fine grits. If you're starting with rough timber or removing old finishes, begin with coarse grits (40-60). This sandpaper grit range effectively removes material and shapes the wood. For initial smoothing and removing imperfections, use medium grits (80-120). To prepare the wood for finishing, switch to fine grits (150-220). For a smooth, final finish before applying varnish or stain, use very fine grits (240-400).
• Metal Sanding: This often involves removing rust, smoothing welds, or preparing surfaces for painting. Start with coarse grits (40-60) to remove rust and heavy imperfections. Use medium grits (80-120) for shaping and smoothing. For final preparation before painting or polishing, use fine grits (150-220). To achieve a polished, high-gloss finish on metal, use very fine to extra fine grits (320-600).
• Automotive Work: Requires meticulous sanding to achieve a flawless finish. For removing old paint and body filler, use coarse grits (40-120). For initial smoothing and shaping, use medium grits (180-320). To prepare the surface for priming, use fine grits (400-800). To achieve a high-gloss, mirror-like finish on the final coat, use extra fine to ultra-fine grits (1000+).
• Drywall Sanding: Aims to smooth seams and remove imperfections for a seamless finish. Start with medium grits (100-120) to smooth seams and remove excess joint compound. Use fine grits (150-220) for final smoothing and feathering. For touch-ups and minor imperfections, use very fine grits (240-320).
• Polishing & Finishing: The goal is to achieve a smooth, high-gloss surface. Begin with fine grits (220-320) to remove light scratches and prepare the surface. Use very fine grits (360-600) for sanding between coats of finish. For achieving a high-gloss finish on hard surfaces like ceramics, plastics, and stone, use extra fine to ultra-fine grits (600 and above).

Sandpaper's versatility stems from its wide range of grit levels, each tailored for specific tasks. Selecting the right grit, understanding wet versus dry sandpaper, and employing progressive sanding techniques are vital for achieving professional results.

Here’s a general overview of common sandpaper grades and their typical applications:

• Extremely Coarse (12-20 Grit): Designed for heavy-duty material removal with machine sanders, primarily used to strip thick finishes from timber.
• Very Coarse (30-36 Grit): Intended for the initial levelling of extremely rough timber surfaces, removing significant imperfections.
• Coarse (40-50 Grit): Effective for removing layers of paint from furniture and aggressively shaping materials.
• Medium (60-100 Grit): Used for shaping wood, including the primary sanding of softer wood types, and preparing surfaces for finer grits.
• Fine (120-180 Grit): Ideal for smoothing bare wood surfaces, eliminating rough textures and preparing for finishing.
• Very Fine (220-280 Grit): Suited for smoothing finishes between coats, ensuring a seamless and even layer before subsequent applications.
• Super Fine/Extra Fine (320-600 Grit): Employed for polishing very hard materials like ceramics, plastics, and stone, achieving a smooth, refined surface.
• Ultra Fine (800-1000+ Grit): Used as a final sanding step on very hard surfaces, creating a highly refined and smooth finish.

Aside from learning about sandpaper grades and their typical applications, it's also important to understand the difference between wet and dry sandpaper and what's progressive sanding.

Dry sandpaper is designed for general sanding tasks on wood, metal, and drywall. It's used without any lubricant and is effective for removing material and smoothing surfaces. Meanwhile, wet sandpaper is designed for use with water or other lubricants. This type of sandpaper is ideal for achieving a high-gloss finish on automotive paint, polishing hard surfaces, and sanding delicate materials. The lubricant helps to prevent clogging, dissipate heat, and create a smoother finish.

As for progressive sanding, this technique starts with the lowest grit sandpaper to allow efficient material removal and shaping and then progressing through the sandpaper grit levels gradually refines the surface, removing scratches left by coarser grits. This process ensures a smooth, even finish and prevents damage to the material.

Beyond grit levels, the type of abrasive material used in sandpaper significantly impacts its performance. Here's a breakdown of common sandpaper types and their ideal applications.

• Aluminium Oxide: This synthetic sandpaper is prized for its longevity and versatility, making it a go-to choice for both woodworking and metalworking. Its ability to maintain sharpness under pressure ensures consistent performance across various projects, from shaping to finishing.
• Silicon Carbide: Known for its exceptional hardness and sharp grains, silicon carbide sandpaper excels in working with very hard materials like stone, glass, and metals. It can be used for wet sanding, where it delivers smooth, refined finishes.
• Garnet: A natural abrasive, garnet sandpaper is valued for its rapid cutting action, especially on softer woods. As it wears, it breaks down into finer particles, providing a progressively smoother finish, though it's less durable than synthetic alternatives.
• Ceramic: A variant of aluminium oxide, it boasts a self-sharpening ability thanks to its microcrystals. With a perfect balance of toughness and hardness, this self-renewing feature ensures the abrasives stay sharp for extended periods, offering superior longevity and performance. It’s also considered one of the best choices to remove heavy-duty paint on metals.
• Emery: Primarily used in metalworking, emery sandpaper features hard corundum grains that effectively remove rust, polish metals, and sharpen tools. Its robust nature makes it suitable for tough metalworking tasks, including surface preparation for welding.

Achieving a flawless finish hinges on proper sanding techniques. Even with the right tools, common mistakes can undermine your efforts. Consider these tips to avoid these pitfalls.

• Using the Wrong Grit: Using a grit rating that’s too coarse can lead to deep scratches and excessive material removal, while a grit that’s too fine may not effectively address the initial imperfections. If you're unsure, consult a sandpaper grit chart to guide your selection.
• Skipping Grit Levels: Each grit level is designed to remove the scratches left by the previous one, and skipping steps forces finer grits to work harder, leading to inefficient sanding and a subpar finish.
• Sanding in One Direction Only: Sanding exclusively in one direction can create noticeable scratch patterns, particularly on wood. Diligently following the wood grain direction helps minimise these patterns and ensures a more uniform finish.
• Not Cleaning Between Sanding Stages: Dust and debris can clog sandpaper and scratch surfaces, leading to uneven finishes. To avoid this, clean between grit levels with a tack cloth, compressed air, or a brush. This simple step also enhances sanding quality and extends sandpaper life.
• Applying Too Much Pressure: Excessive pressure during sanding causes uneven removal, wears sandpaper prematurely and creates deep scratches. Instead, use light, consistent pressure, letting the grit do its job.