A Guide to Sandpaper Grits and Their Uses in Woodworking

As a woodworker, choosing the right sandpaper is as crucial as selecting the wood itself. Knowing the ins and outs of sandpaper grits is essential for achieving the finish you want, whether that’s a smooth, polished surface or a textured look.

Let’s break down the world of sandpaper grits, how they’re used, and why each grit matters for different stages of woodworking.

Understanding Sandpaper Grit Numbers

The grit number on sandpaper refers to the size of the abrasive particles on its surface. Higher numbers mean finer abrasives, which lead to smoother finishes, while lower numbers have coarser grits, ideal for rougher work.

In woodworking, common grit numbers range from around 40 to 400, though there are grits even finer and coarser. Here’s a basic breakdown:

• 40-60 Grit – Coarse
• 80-120 Grit – Medium
• 150-220 Grit – Fine
• 320+ Grit – Very Fine

Each grit serves a purpose, and using the right one can save you time and effort.

Coarse Grits: 40-60 Range

When to Use Coarse Grits

Coarse grits like 40 and 60 are best used for initial sanding steps. They’re perfect for heavy stock removal, shaping, or smoothing out rough surfaces.

If you’re working with rough-sawn lumber, a coarse grit can help you knock down high spots and remove saw marks efficiently.

Coarse grits also help if you’re working with wood that has glue or finish that needs to be stripped away. However, remember that coarse grit leaves scratches, so plan to follow up with finer grits to remove these marks as you progress.

Tools and Techniques for Coarse Sanding

For coarse sanding, consider using a belt sander or a random orbital sander. Belt sanders work quickly but are aggressive, so go easy to avoid gouging the wood.

Random orbital sanders are gentler and easier to control, which makes them a solid choice if you’re new to sanding. Be sure to keep the sander moving to avoid uneven sanding marks.

Medium Grits: 80-120 Range

When to Use Medium Grits

The 80-120 grit range is where the real shaping and refining begin. Medium grit is often used after coarse sanding to further smooth the surface without removing too much material.

It’s ideal for preparing the wood for finer grits and getting rid of the roughness left behind by coarse sandpaper.

For instance, if you’re building a table, once you’ve done the initial shaping and leveling with coarse grit, switching to 80 grit will help you refine the edges, even out the surface, and start creating a smoother finish.

Best Practices for Medium Grit Sanding

When using medium grit, you might switch to a hand sanding block, especially if you’re working on edges or smaller parts. Hand sanding gives you better control in detail areas like corners and edges.

However, a random orbital sander will also do a great job on larger surfaces. Remember to sand along the grain, not against it, to avoid scratches that will show up in the final finish.

Fine Grits: 150-220 Range

When to Use Fine Grits

Once your surface feels smooth and free of major imperfections, you’re ready for fine-grit sandpaper. The 150-220 range is ideal for the final stages of prep work before applying finish. It’s also perfect for removing any fine scratches left from the previous steps.

Fine grit is especially helpful if you’re working with a softer wood like pine, as it allows you to smooth the surface without damaging it. For hardwoods, it brings out the wood grain’s natural beauty, preparing it for stain or varnish.

Techniques for Fine Grit Sanding

With fine grit, hand sanding is often best, especially if you’re going for a smooth, flawless finish. A light touch is key here; pressing too hard can create uneven spots.

If using a power sander, make sure to reduce the pressure and keep it moving smoothly across the surface.

Very Fine Grits: 320 and Up

When to Use Very Fine Grits

Very fine grits, 320 and above, are mostly used between finishing coats or to achieve an extra-smooth finish on the wood itself. Once your piece is sanded to a fine grit, very fine sandpaper can be used to get a glass-like finish before applying stain, varnish, or lacquer.

If you’re working on a high-end piece, such as a furniture piece with intricate details, using very fine grits helps create that professional-level finish. You might also use this grit range for a quick “buffing” after each layer of finish.

Techniques for Very Fine Grit Sanding

With very fine grits, it’s usually best to sand by hand, especially between finish coats. Sand gently with the grain to avoid sanding through the finish layer.

You’ll be able to see and feel if the finish needs more smoothing. Many woodworkers use a light mist of water or even fine steel wool in this stage, as it can help highlight any imperfections before the final finish is applied.

Choosing the Right Sandpaper Material

Sandpaper isn’t just about grit; it also comes in different materials, which affect its durability and effectiveness on various wood types:

• Aluminum Oxide – Durable and affordable, aluminum oxide sandpaper is common for most woodworking projects and works well on both soft and hardwoods.
• Garnet – Known for its soft, natural finish, garnet sandpaper is excellent for fine sanding and is often preferred for final sanding steps before finishing.
• Silicon Carbide – Stronger and sharper than aluminum oxide, this type is ideal for sanding metal and finishes but can also work on wood for ultra-smooth finishing tasks.
• Ceramic – Ceramic sandpaper is highly durable and best for heavy-duty sanding but can be expensive. It’s often used with power sanders for shaping and rough sanding.

Tips for Getting the Best Results

1. Start Coarse and Work Your Way Up: Always start with a coarser grit to remove any large imperfections, then work your way up to finer grits. Skipping grits often leaves scratches that are hard to remove in later stages.
2. Sanding Along the Grain: Sanding along the grain helps prevent scratches. Cross-grain scratches are difficult to see until you apply the finish, so avoid sanding against the grain whenever possible.
3. Clean Between Grits: After each sanding step, remove the dust with a vacuum or tack cloth. Dust from coarser grits can cause scratches if left on the wood when you start with a finer grit.
4. Light Pressure on Power Sanders: When using power sanders, let the weight of the tool do most of the work. Pushing too hard can lead to swirl marks that show up after finishing.
5. Use Fresh Sandpaper: Worn sandpaper doesn’t cut efficiently, meaning it’ll take longer to get the same results and may leave uneven surfaces. Replace your sandpaper regularly to ensure a consistent finish.

Practical Applications in Woodworking Projects

Whether you’re building a piece of furniture, a cabinet, or a decorative item, knowing how to choose the right sandpaper grits is vital. Here are a few examples:

• Furniture Making: For tables and chairs, start with 80-grit for shaping, move to 120 for smoothing, and finish with 220 before staining. For high-end pieces, consider using 320 or higher to polish.
• Cabinetry: Sand all surfaces with 120-grit first, especially if you’re working with hardwood. Then use 220 grit for the final sanding. Cabinets often have detailed parts, so hand sanding is often necessary for corners.
• Decorative Items: Smaller pieces, such as wooden boxes or decor items, can usually start at 120 grit and go straight to 220 grit since they don’t typically need as much shaping or leveling.

Building a Sanding Routine

In woodworking, sanding is more than just a chore; it’s a skill that takes practice to master. Having a clear understanding of sandpaper grits and their uses helps you achieve better results in your projects. Starting coarse and moving up through the grits will make all the difference in the finish quality.

Follow a consistent sanding routine, and remember to let the tools do the work for you. Each step in sanding brings you closer to creating a beautiful, professional-quality piece that you’ll be proud to show off.