How to Use a Random Orbital Sander

Learn how to effectively use an orbital sander to strip old finishes, smooth rough surfaces, and ready projects for painting and staining.

Published on February 21, 2023

If you're a seasoned DIYer, you've likely used a random orbital sander. But those new to home improvement projects or carpentry might be in need of a crash course on this handy power tool. When used correctly, a random orbital sander is highly efficient at removing old finishes, smoothing rough surfaces, and prepping projects for new finishes.

While a random orbital sander might seem easy to use, a few tips and tricks will help you get the most out of this power sander, saving you time and giving your DIY projects a professional edge.

What Is a Random Orbital Sander?

A random orbital sander is a power sander that utilizes a round sandpaper disc attached to a head that moves in both a random vibrating motion and a spinning motion. The randomized movement of the head creates a smooth surface on a variety of materials, including plastic, wood, and metal, without showing obvious sanding marks.

Types of Orbital Sanders

Not all orbital sanders are the same. In fact, the random orbital sander operates completely differently than a standard orbital sander.

1/4-Sheet Orbital Sander

A 1/4-sheet orbital sander gets its name from its size. The square pad is big enough to hold 1/4 of a 9x11 sandpaper sheet.

1/2-Sheet Orbital Sander

You guessed it: A 1/2-sheet orbital sander gets its name from its ability to use 1/2 of a 9x11 sandpaper sheet.

Random Orbital Sander

Unlike 1/4- and 1/2-sheet orbital sanders, a random orbital sander uses a prefabricated piece of sandpaper that's round. Additionally, a random orbital sander rotates while vibrating, while the 1/4- and 1/2-sheet orbital sanders simply vibrate. This random, dual-motion helps to hide sanding marks.

Choosing Sandpaper Pads

When shopping for sanding pads for a random orbital sander, you'll find that most options feature the same design, with some variation between brands. Standard random orbital sanders have 5-inch pads with holes for dust collection. The corresponding sanding pads are 5 inches wide with pre-cut holes that line up with the sander.

Once you've identified the corresponding pads, you must choose the appropriate grit for the task at hand, which will be represented by a number on the packaging. The lower the number, the coarser and more aggressive the sandpaper. Use the guide below to get a basic understanding of how to understand sandpaper grit numbers.

60 and below: These grits are great for stripping old finishes or the beginning stages of smoothing extremely rough material.

80 to 150: Grits in this range are also great for stripping finishes and smoothing materials, but are much less aggressive than lower grit numbers.

180 to 220: Once you pass 180, the sandpaper is within the finishing range. While these grits can also be used to strip finishes and smooth materials, they are much less efficient. These grits are mostly utilized for prepping surfaces for paint or stain.

320 to 400: Grits in this range are often utilized for ultra-smooth finishes and sanding between coats of finishes.

How to Use a Random Orbital Sander

Follow the steps below to effectively use your random orbital sander.

What You'll Need

Random orbital sander
Sandpaper discs in assorted grits
Dust collection bag or vacuum with adapter
Dust mask and eye protection

Step 1: Attach the Sandpaper

Attach the sandpaper to your sander's pad by aligning the holes in the paper with the holes in the pad and pressing the paper firmly and evenly into the pad. Start with your most aggressive grit.

If you find that your sandpaper won't stay on the sander, you may need to clean or replace the pad. First, try removing any dust and debris form the pad, then gently brush it with a wire brush. If this doesn't improve its holding power, purchase the appropriate replacement pad and install it on your sander.

Step 2: Attach the Dust Bag

Install the dust collection bag that came with your random orbital sander. For improved dust collection, use an adapter to install a wet/dry vac to the tool instead.

Step 3: Secure the Material

When working on small pieces, secure them to your work surface using clamps.

Step 4: Sand the Material

Holding the sander evenly on the material's surface, turn on the power and immediately start moving the sander. With a random orbital sander, sticking with the grain of the material isn't pertinent, but you may find that this results in a better end result. As you move the sander across the material, refrain from pressing down too firmly. Instead, let the tool's rotation and vibration do the work.

Once you're finished or ready to change the paper, lift the sander off the material and switch it off.

Failing to hold the sander evenly on the material will result in an uneven surface with gouges.

Step 5: Replace the Sandpaper

Once your sandpaper is no longer effectively removing material, remove it and install a new piece. If you are ready to progress grits, choose the next grit with a higher number.

Step 6: Repeat Process

Repeat the sanding process, progressing grits until you reach your final desired grit. For most projects, aim to progress at least three grits. On some projects, it might be worthwhile to follow the random orbital sander with a final hand-sanding using a higher grit and sticking to the direction of the grain.

How to Keep a Random Orbital Sander in Good Condition

Once you're finished with your random orbital sander, remove and empty the dust collection bag, remove the sandpaper, and blow out all dust from the machine. Store the sander in a protective tool bag or box with the dust collection bag removed and the cord loosely wrapped. If using a cordless sander, remove the battery while storing. Replace the sanding pad as needed.

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