Sandpaper grit chart & grits explained

1. Understanding Sandpaper Grit

What is Sandpaper Grit?

Sandpaper grit is the number of cutting points visible from the surface. These particles help finely grind or plane material or process things. Grit numbers indicate particle size, with lower numbers being coarser and higher numbers being finer. Grain size controls how rough or mild sanding is and the final surface polish.

Importance of Sandpaper Grit

Impact of Grit Size on Surface Finish:

• Coarse grits(e.g. 40-60) are used where the material is to be removed quickly, such as paint or steel with an uneven outer layer.
• Fine grits (e.g. 220-400) are applied to get a smooth surface that is ideal for polishing and more detailing work.

Impact on Material Removal Rate:

• The coarser forms also cut rapidly, thus perfect for tasks that require the removal of more material.
• A fine gritremoves less of the material, which makes it useful in certain tasks where one needs more control in the operation as well as in the finishing stages.

Importance of Selecting the Right Grit:

• It is also possible to select the wrong gritwhich upon use results in achieving the right finish albeit damaging the material.
• Appropriate selection of gritmakes the work on sanding much easier, and faster and produces better results than when a wrong grit is used.

2. Sandpaper Grit Chart

Overview of Grit Categories

Sandpaper grits are grouped according to the particle size where small particles act in removing a lot of material as compared to the large particles. There are four categories of sandpaper and each has its ideal use in sanding and finishing: coarse, medium, fine, and ultra-fine.

Detailed Grit Chart

Coarse Grits (40-60)

Description: Coarse grits are developed for starting cutting and rough shaping based on the application of strong pressure.

Typical Uses: This involves scraping off previous coats, sanding rough surfaces of wood, and cutting edges for strength use.

Medium Grits (80-120)

Description: These medium grits are suitable for general sanding and for giving the surface a fine finish in preparation for the final polishing.

Typical Uses: Some of the benefits include: Straightening edges and contours, evening out surfaces, as well as declassing one’s work to ready the surface for painting or staining.

Fine Grits (150-220)

Description: The fine grits are employed when a perfect polish or a fantastic smooth surface is desired on the workpiece.

Typical Uses: Ideal for surface preparation before applying the last coat of lacquer, stain, or paint or for every inter-coat sanding.

Ultra-Fine Grits (240 and above)

Description: Ultra-fine grits are designed for polishing and achieving a high-gloss finish.

Typical Uses: Ideal for polishing metal, plastic, and wood, and achieving a smooth, mirror-like finish.

3. How to Use Sandpaper Effectively?

Proper Sanding Technique

• Always sand in the direction of the grain to avoid scratches or damage, especially when working with wood.
• Apply even, gentle pressure to ensure uniform material removal. Too much pressure can lead to uneven surfaces or premature sandpaper wear.
• Move the sandpaperin smooth, controlled motions, avoiding circular patterns unless using a specific tool designed for it, such as an orbital sander.

Sanding Tools and Accessories

• Sanding Blocks: Help distribute pressure evenly and provide more control during hand sanding.
• Orbital Sanders: Ideal for larger surfaces, offering consistent sanding with minimal effort.
• Sanding Sponges: Great for sanding contours, corners, and irregular surfaces.

Using the right tool or accessory can enhance efficiency and produce better results.

Maintaining Sandpaper

• Cleaning: Use a sandpaper cleaning block or an old brush to remove dust and debris from the sandpaper’s surface, prolonging its usability.
• Storage: Store sandpaper in a cool, dry place to prevent moisture from weakening the abrasive particles or causing paper backing to curl.

Maintaining your sandpaper ensures that it performs efficiently and lasts longer, saving time and money.

4. Common Mistakes to Avoid

Using the Wrong Grit

• Consequences: Using a coarse grit paperpenetrates deep into the material, creating gouges and harming fragile surfaces, or a thin grit will not shave or remove material/blemishes.
• Tips: Sandpaper is classed by grit, so start with a coarse grit for rough work and a fine one for precise work. [IC] Use the sandpaper grit chart to determine the best grit for washing and scraping.

Applying Too Much Pressure

• Consequences: Being forceful can result in poor sanding, scratches on the surface as well as fast exhaustion of the sandpaper.
• Tips: Use mild, even pressure to cut or wear down the wall using sandpaper. This prevents regular sharpening of the cutting edge, giving the surface a glossy, easy finish and increasing the Sand paper's longevity.

Skipping Grits

• Consequences: Skipping gritsmay damage the surface or make it resistant to fine grits, resulting in a poor finish.
• Tips: Step up through grits beginning with a rough grit, followed by progressively finer grits. This allows perfect, professional results without creating impressions that are deep on the skin.