A random orbital sander, also known as a random orbit sander, is an essential power tool for any DIYer or woodworking enthusiast. This versatile sander can be used for everything from removing old finishes to achieving a flawless smooth finish on wood. Learning how to properly use a random orbital sander will enable you to complete projects faster and achieve better results. In this comprehensive guide, we will cover everything you need to know about how to use a random orbital sander.
Selecting the Right Random Orbital Sander
When choosing a random orbital sander, there are several factors to consider:
Orbital Size
The orbital size refers to the diameter of the circular sanding motion. Smaller 3-4 inch orbital sanders are ideal for detail work and sanding in tight spots. Larger 5-6 inch orbital sanders work well for sanding large flat surfaces.
Speed Settings
Variable speed settings allow you to match the sander’s orbits per minute (OPM) to the task at hand. Lower speeds around 8,000 OPM are best for fine finishing work. Higher 12,000+ OPM speeds help remove material faster.
Dust Collection
Random orbital sanders with built-in dust collection keep your work area clean and you breathing easy. Models without dust collection will require a shop vac attachment.
Cordless vs Corded
Cordless sanders provide unlimited mobility but run time is limited by battery life. Corded models offer continuous run time but limit your range of motion.
For most general purpose sanding, a 5-6 inch orbital sander with variable speeds and dust collection is recommended. Models from reputable brands like DeWalt, Bosch, Makita, and Festool are excellent choices for most users.
How to Use a Random Orbital Sander
Follow these steps to safely and effectively use a random orbital sander on your next woodworking project:
1. Select the Right Sandpaper Grit
- Start with a coarse 60-80 grit sandpaper to remove material and level surfaces
- Use 100-120 grit for smoothing between coats of finish
- Finish with 150-220 grit to achieve a super smooth surface
Match the sandpaper’s grit rating to the task at hand for best results.
2. Attach the Sandpaper Properly
- For models with peel-and-stick sanding disks, remove the protective backing and adhere the sandpaper to the pad.
- For sanders with clamps or other fasteners, secure the sandpaper tightly to prevent slipping.
Improper sandpaper installation can lead to inconsistent sanding.
3. Prepare the Work Surface
- Clear the area of any dirt, dust or debris that could scratch the surface
- Remove any hardware or obstructions in the sanding path
- Cover adjacent surfaces to prevent accidental damage
Proper preparation prevents accidental damage and allows for smooth sanding.
4. Adjust the Speed Setting
- Use lower speeds (8,000-10,000 OPM) for final smoothing and finishing
- Higher speeds (12,000+ OPM) help agressively remove material
- Find the ideal speed for the sanding task at hand
The correct speed setting helps achieve the desired sanding results.
5. Maintain a Proper Grip
- Wrap both hands around the sander for maximum control
- Avoid gripping too tightly or pressing down hard
- Let the sander’s weight provide the sanding pressure
Proper grip prevents gouging, uneven sanding, and fatigue.
6. Move the Sander in Small Overlapping Circles
- Work in manageable sections, not the entire surface at once
- Overlap the circles by 50% for consistent sanding
- Move at a steady rate to avoid uneven scrub marks
Overlapping circles help ensure an uniformly sanded surface.
7. Routinely Check Your Progress
- Stop periodically and examine the surface
- Look for scratched or wavy areas needing more attention
- Feel with your hand for smoothness
Frequently inspecting your work prevents over or under sanding.
8. Clean the Sanded Surface
- Use a brush or vacuum to remove dust between sanding grits
- Wipe clean with a dry cloth before finish application
- Clean sandpaper between uses for better performance
Proper cleaning gives finish materials the best surface to adhere to.
9. Follow Finish or Next Step Recommendations
- Some finishes require finer 220+ grit sanding
- Wood putty or gluing may need rougher 80-100 grit scratch patterns
- Always read manufacturer instructions!
Sand and prepare surfaces appropriately for optimal results.
By following these techniques, you can efficiently sand wood surfaces to the desired smoothness your project requires. It just takes practice and experience to master random orbital sander use.
Sanding Techniques for Different Needs
The beauty of a random orbital sander is its flexibility to handle a wide variety of sanding tasks. Here are some of the most common sanding techniques and what grit sandpaper they require:
Removing Old Finish
- Use 60-80 grit to aggressively remove old paint or finish
- Helpful for refinishing furniture or stripping wood
- Creates deep scratch patterns for adhesion of new finish
Leveling Surfaces
- Flatten uneven boards with 80-100 grit
- Also good for removing saw marks from rough wood
- Helps create a flat smooth base for further sanding
Smoothing Between Coats
- Lightly sand with 120-150 grit between finish coats
- Smooths dust nibs and fibers for an even coat
- Prepares the surface for additional layers of finish
Final Smoothing
- Use 180-220 grit for final smoothing
- Eliminate small scratches and swirl marks
- Leaves a perfectly smooth sanded surface ready for finish
Fine Woodworking
- Sand projects up to 320-400 grit for a glass-like feel
- Removes even the slightest surface imperfections
- Required for rubbing out finishes to a mirror polish
Selecting the appropriate grit sandpaper for the job will help you achieve the desired results quickly and efficiently.
Sanding Tips and Tricks
After years of using them, I’ve picked up some helpful tips and tricks for getting the most out of random orbital sanders:
- When changing sandpaper grits, always sand perpendicular to the previous grit’s scratches for the smoothest finish. The new grit will smoothly remove the previous scratches.
- Fold sandpaper into a square pad when sandingprofiled edges. The folded edge helps prevent rounding over corners.
- Let the sander do the work. Avoid pressing down hard. The random orbits provide plenty of sanding action without added pressure.
- Periodically drag the edge of the sander in a straight line to help identify any remaining deep scratches.
- Use an interface pad between the sander and sandpaper when working on curved surfaces. This helps optimize sanding contact on irregular shapes.
- When finishing open-grained woods like oak or walnut, sand diagonally to the wood grain to avoid digging into the soft earlywood.
- Wiping surfaces lightly with a damp cloth raises the grain. Let dry, then sand again for an ultra-smooth sanded surface.
- When sanding edges, run the sander so the pad overhangs the edge to prevent rounding over.
- For cleaning clogged sandpaper, rub on a stick of ordinary wax then power through on scrap material. The wax clears the pores of packed sawdust.
Hopefully these tips will help save your fingers and get you better results with your random orbital sander!
Sanding Different Materials
While primarily used for sanding wood, random orbital sanders can also be used to sand and finish a variety of other materials:
Metal
- Avoid coarse grits that create deep scratches
- Use 120-220 grit to smoothly sand and polish metal surfaces
- Makes quick work of removing rust before painting
Fiberglass
- Start with 100 grit to level and smooth gel coat
- Works well for shaping and fairing composite materials
- Finish sand with 220 grit for glossy coatings
Drywall
- Quickly sand away high spots and mud texture
- Produces very fine dust requiring good ventilation
- Final sand walls with 150-220 grit before painting
Concrete
- Aggressively profile and roughen concrete with 60-80 grit
- Opens pores for increased paint adhesion
- Smooths rough edges on pavers
While best for woodworking, random orbital sanders are suitable for effectively sanding almost any material when paired with the appropriate abrasive.
Sanding Challenges and Solutions
Sanding can present some frustrating challenges at times. Here are some common issues and how to overcome them:
Problem: Swirl Marks and Scratches
- Solution: Ensure the previous grit scratches are completely removed by sanding perpendicular to them. Gradually step up sandpaper grits for a smooth scratch-free surface.
Problem: Chatter Marks
- Solution: Chatter marks cause waving and ridges on the sanded surface. Avoid pressing too hard, keep the sander moving constantly, and ensure adequate sandpaper conditioning with wax.
Problem: Edge Rounding
- Solution: When sanding surfaces adjacent to edges, slightly overhang the pad to keep the edge crisp. Use a sanding block instead of a random orbital sander along edges.
Problem: Pigtails or Holograms
- Solution: These show up on finishes as spiraling swirl marks. They indicate the prior sanding step was too aggressive. Go back and sand again with a finer grit before applying finish.
Problem: Burn Marks
- Solution: Aggressive sanding with too little movement in one area can cause burns. Keep the sander moving constantly at proper speeds to avoid heat buildup.
Problem: Uneven Sanding
- Solution: Pay close attention to sanding direction and make sure to feather out unevenly sanded areas. Applying even pressure and overlapping pass patterns helps prevent this.
With attention to speed, grit selection, sanding direction, and technique, you can overcome these common sanding problems.
Safety Tips
While extremely useful tools, random orbital sanders introduce some safety considerations:
- Wear eye and hearing protection – sanding produces debris and high decibel noise.
- Use a dust mask or respirator – wood dust is extremely harmful to lungs.
- Avoid overexposure to vibration by taking frequent breaks – this reduces fatigue and potential hand-arm vibration syndrome.
- Ensure good workpiece clamping – this prevents abrasive catches and violent workpiece movement.
- Check electrical cords for damage – cracked insulation can expose live wires.
- Don’t exceed maximum recommended sandpaper grit – too fine of sandpaper can cause motor overload.
- Unplug when inspecting, cleaning, or changing abrasives – accidental startup can cause injuries.
By keeping these safety tips in mind, you can prevent injuries and safely enjoy the benefits of random orbital sanding.
Frequently Asked Questions
Answers to some common random orbital sander questions:
What are the differences between orbital and palm sanders?
- Palm sanders move in direct straight-line motions, while orbital sanders move in random elliptical orbits. The orbital motion of ROS sanders results in a swirl-free scratch pattern.
How fast should I move the sander across the surface?
- As a general rule of thumb, move the sander across the workpiece at about 1 foot per second. This prevents uneven scrub marks while still achieving good cutting action.
How hard should I press down when sanding?
- You want to apply just enough downward pressure to keep the sander base flush to the surface. Too much pressure can lead to rapid sandpaper clogging. Let the sander do the work.
How do I know what grit to start with?
- For removing a lot of material, start with 60-80 grit. To smooth between finish coats, begin with 150-180 grit. To simply smooth a surface, start with 120-150 grit.
Do I need a dust collection system?
- Dust collection is highly recommended. Random orbital sanding produces large amounts of fine dust that is hazardous to breathe and destructive to machinery. Dust extraction keeps everything cleaner and functioning optimally.
When do I need to change the sandpaper?
- Replace sandpaper disks once their cutting action seems to slow down and they start leaving behind a gray burnished surface instead of fresh wood exposure. Also replace once they become clogged with sawdust and debris.
Conclusion
Learning how to effectively use a random orbital sander is a valuable skill for DIYers and woodworkers. With the right techniques, these sanders can efficiently handle a huge range of sanding challenges. The key is picking the appropriate grit for the task, maintaining proper sanding pressure and direction, and taking precautions against common sanding problems. Employing the strategies outlined in this guide will help you achieve expert results. With practice, you’ll soon be able to transform rough surfaces into glassy smooth masterpieces using your random orbital sander.