The Basics on Sanding

Sanding wood is a fundamental step in woodworking that smooth the surface and remove imperfections. Here we will cover:

Part 1: What Is Sandpaper?

Part 2: The Different Grits

Part 3: Process and Technique Overview

Part 4: Hand and Power Sanding Tools

 

Part 1 - What is Sandpaper?

Sandpaper is a coated abrasive product that consists of abrasive particles adhered to a flexible backing material.

Backing Material: The backing material provides support and flexibility to the sandpaper. It can be made from various materials such as paper, cloth, polyester, or a combination of these. The choice of backing material influences the durability and flexibility of the sandpaper.

Abrasive Particles: The abrasive particles are the key element of sandpaper. These particles are bonded to the backing material using adhesives. The abrasive particles have sharp edges that cut into the material being sanded.

Grit Size: Grit size refers to the number of abrasive particles per square inch on the sandpaper. Lower grit numbers indicate coarser abrasives, while higher grit numbers indicate finer abrasives. Coarse grits (e.g., 40-80) are suitable for removing material quickly, while finer grits (e.g., 220-400) are used for finishing and smoothing surfaces.

Sandpaper is available in various forms, including sheets, rolls, belts, and discs.

 

Part 2 - The Different Grits

Using a progressive sequence from coarse to fine, is a common practice in sanding to achieve the best results. Each grit serves a specific purpose in the sanding process:

Coarse Grit (Lower Number):

Purpose: Coarse grits, such as 40 to 80, are used for the initial sanding to remove significant material, surface imperfections, and irregularities quickly. They are efficient at leveling surfaces and shaping wood.

Applications: Ideal for tasks like removing rough mill marks, leveling uneven surfaces, or preparing a piece of wood for finer sanding.

Medium Grit (Intermediate Number):

Purpose: Medium grits, usually in the range of 100 to 150, are used to refine the surface after coarse sanding. They help remove the scratches left by the coarse grit, making the surface smoother.

Applications: Suitable for preparing the wood for finishing, refining shapes, and smoothing out any remaining coarse marks.

Fine Grit (Higher Number):

Purpose: Fine grits, such as 180 and above, are used for the final sanding stages to achieve a smooth and polished finish. They remove the scratches left by the medium grit, resulting in a surface ready for staining, painting, or applying a finish.

Applications: Essential for achieving a fine finish on woodworking projects, ensuring a polished appearance and allowing finishes to adhere properly.

 

Why Use a Progressive Grit Sequence?

Efficient Material Removal: Coarse grits efficiently remove material and surface imperfections, saving time and effort in the initial stages of sanding.

Surface Smoothing: Progressing to medium grits helps smooth the surface further, eliminating the coarse scratches and preparing the wood for finer sanding.

Polished Finish: Fine grits contribute to achieving a polished and refined finish. They help remove the smaller scratches left by the medium grit, resulting in a smooth surface ready for the final touches.

Optimal Finish Adhesion: Using a fine grit ensures that the surface is sufficiently smooth for finishes like paint, stain, or clear coats to adhere properly.

Reduced Sanding Marks: Each successive grit helps reduce the visibility of sanding marks, ensuring a more uniform and professional-looking result.

 

By following a progressive grit sequence, you can work efficiently, achieve a smoother and more refined finish, and prepare the surface for the final treatment. It's a systematic approach that contributes to the overall quality of the woodworking or finishing project.

 

Part 3 - Technique Overview

Achieving the best sanding results involves not only choosing the right sandpaper and tools but also employing effective sanding techniques.

1. Progressive Grits: Start with a coarse grit to remove material and imperfections, then progress to finer grits for a smoother finish. The general rule of thumb is to only increase your grit by half of your current grit.  So if you are using 80, you should then go to 120, 120 then to 180 and so on.
2. Check Your Progress: Periodically inspect the surface for scratches and imperfections. If necessary, go back to a coarser grit to address any remaining issues before progressing to finer grits.
3. Use a Sanding Block: When hand sanding, use a sanding block or pad. This helps distribute pressure evenly and ensures a flat surface. It also prevents over-sanding in certain areas.
4. Apply Even Pressure: Apply even pressure while sanding to avoid creating low or high spots. Uneven pressure can result in an uneven surface.
5. Sand with the Grain: Always sand in the direction of the wood grain. Sanding against the grain can create scratches that are more difficult to remove, and it may lead to an uneven finish.
6. Change Sandpaper Regularly: As sandpaper wears out, its effectiveness diminishes. Change to a fresh sheet or disc regularly to maintain optimal sanding performance.
7. Keep It Clean: Clean the workpiece and the sandpaper regularly to prevent clogging. Clogged sandpaper is less effective and can leave undesirable marks on the surface.
8. Be Patient: Sanding is a gradual process. Take your time, especially with finer grits, to achieve a smooth and polished finish.

 TIP: One technique that is popular is to take a pencil and lightly mark all over your sanding surface between each grit, that way you know what areas you have or have not sanded yet.

Remember, the key to successful sanding is patience, attention to detail, and the use of proper techniques. Whether hand sanding or using power tools, following these guidelines will help you achieve the best results for your woodworking projects.

 

Part 4 - Hand and Power Sanding Tools

There are various sanding tools available, ranging from simple handheld tools to more advanced power sanders. The choice of sanding tool depends on the type of project, the material being worked on, and the desired finish. 

 Common Manual Sanders:

• Handheld Sanding Blocks: These are simple blocks made of wood or rubber with a surface to attach sandpaper. They provide a firm and flat surface for hand sanding.
• Sanding Sponges: Flexible and handy for contoured surfaces
• Files and Rasps: Used for shaping and smoothing wood before finer sanding.

 

Common Power Sanders:

• Belt Sander: Features a continuous loop of sandpaper that rotates around two drums. Ideal for quick material removal on large, flat surfaces.
• Orbital Sander: Moves in small, orbital patterns. Suitable for finishing and general sanding on flat surfaces.
• Random Orbital Sander: Combines orbital and rotary movements, providing a swirl-free finish. Versatile for various sanding tasks.
• Disc Sander: Uses sanding discs for smoothing and shaping wood.
• Spindle Sander: Designed for sanding curved or contoured surfaces.

 

While there are many more specialized sanding tools available, these basics can be used to complete almost any task.  Choosing the appropriate sanding tool based on the specific requirements of your project is important. Always follow safety guidelines, wear appropriate protective gear, and use the correct sandpaper grit for optimal results.