A guide to sanding wood with an orbital sander

Once anyone gets into woodworking, they quickly discover there many power tools that are used. One of the most often used is the random orbital sander, sometimes simply called an orbital sander. It has many applications outside woodworking, and can do both heavier jobs and fine finishing jobs. 

Most wood needs sanding to remove marks from sawing, milling or any handling. If you’re thinking of purchasing an orbital sander, you will probably need to familiarize yourself with its proper use. Follow this guide to learn how to sand wood using this versatile tool. 

Before You Start

It is always a good idea to exercise safety precautions when working with any electrically powered tools. Whenever you are using a power tool, you should be confident that it is in working condition and is not faulty. Do not use any machine that has been recalled, and if you have a used machine, check it thoroughly. Regularly inspect your power tools to avoid running into problems at the last minute. 

A dust mask, safety goggles, gloves, and hearing protection are all standard equipment you may consider using when operating any power tools. These are important to avoid any hazards that you may come across while working, such as airborne sawdust, and the loud noise of the motor of a power tool, or vibrations. 

These are additional precautionary actions you should take when using an orbital sander:

• Always be mindful of the cord, to avoid tripping over it or accidentally sanding it. Also make sure you can reach your entire workspace without pulling it taut. If you need to use an extension cord, make sure it is compatible with your sander, and safe to use. 
• Keep a firm grip on the sander, the motor is strong enough for it to move around when not held in place.
• Disconnect the tool before changing the sandpaper to avoid any mishaps. Switching it off (using the button) is also an option, but disconnecting is safer.
• Make sure both your workbench and the item you want to sand are stable and secure, otherwise, they might move when in contact with the vibrating sander.
• Empty out the dust collection bin, and always keep the ventilation slots clear of any dust. If the ventilation is blocked with sawdust, it could lead the motor to overheat. 
• If you are using one hand to control the sander, make sure to keep your other hand away from the sander. 

Choosing and Attaching Sandpaper

The sandpaper for a random orbital sander comes as a circular disc that should be attached to the machine. There are two ways to attach the sandpaper discs: hook and loop fasteners, or an adhesive. The hook and loop fasteners (Velcro) are easier to use and faster for changing sandpaper discs. 

Several different abrasive materials are used in sandpaper, and not all are interchangeable. Some types are not suitable for use on wood. Most manufacturers give instructions on the packaging, stating what materials the sandpaper can be used on, as well as its coarseness. You might need to use more than one type of sandpaper on the same wooden surface, as some are more suited for coarse sanding, and some are better for polishing. 

Keep in mind that you will need to select grit sizes as well. You should always begin with coarse sanding, using sandpaper of a lower grit size. After sanding down the first layer of wood, gradually increase the grit size for fine sanding, until you finally polish the wood to your liking. If you are sanding and polishing wood that does not need too much sanding, you should start with a medium fine (or fine) grit, and work your way up to extra fine grit. The important thing to remember is that as you repeat the sanding process, each consecutive grit size should be higher than the previous one. 

Sanding 

Mark the wood using a lead pencil or chalk, using a zigzag line across the entire surface. This will ensure you cover the entire area, and only go through it only once per grit size. It acts as a clear visual guide for the parts that you have covered and the parts that still need to be sanded. 

Make a habit to put your sander on the wooden surface first, and only turn it on after securing it with a firm grip. This is not only a safety precaution, it helps prevent the sander from grabbing, as it could scratch the wood. Fixing scratches is not always an easy process, but can easily be avoided with this tip.

With the least pressure you can manage, start gliding the sander back and forth. Start coarse sanding (using the lower grit size) from one end of the surface, and work your way to the other end. Use overlapping passes to ensure that you are getting every last inch of the surface. If the surface you are sanding is narrow, you may move the sander in a circular motion. Moving with the grain of your wooden surface is not crucial, but yields better results.

The entire surface needs to be sanded (in fact, all the wooden surfaces in your project), so be patient. Do not rush the process, as you will need to keep your pace slow and steady. The usual recommendation is that you should be able to cover about a foot of wooden surface in ten seconds. If you move too fast, too slow, or at a changing pace, the result is likely to be uneven. 

Keep the sander flat against the wood at all times, to avoid gouging. If you see any ridges or problem areas, do not tilt the sander in an attempt to fix them. Tilting will cause gouging and scratches. With the sander flat, the coarse sandpaper will be able to remove the ridges. You may sand the ridge manually if it is especially difficult. 

After you have finished the entire area with the lower grit sandpaper, you will need to change to a finer sandpaper. Take the sander off the surface first, then turn it off. This is to avoid the sander from skidding to a stop, which would leave swirling marks on your wood. 

Once you have turned off (and preferably disconnected) the sander, change to a higher grit sandpaper for fine sanding. You should have been able to remove the all pencil or chalk marking using the coarse sandpaper, and thus need to mark the wood again before fine sanding.

Additional tips

•  Attach a vacuum to your random orbital sander, especially if your project is big. You may need to purchase an adapter to connect the dust bag/ventilation hole to a vacuum. This will ensure your workplace is clean, in addition to increasing the efficiency of your sander.
• If you are working on sanding solid wood floors, a drum sander would be a better choice than an orbital sander. But if you don’t want to spend so much on a bulky tool, you can make a DIY drum sander with a few melamine sheets and MDF.
• When purchasing sandpaper discs, try to match the holes to the holes in the sanding pad of your sander. These holes are for the suction and if they are blocked could result in overheating the motor, and clogging the sander. 
• Even though you need to use coarse sandpaper and keep changing it for finer grit; it isn’t necessary to go through all the grit sizes. Three or four grit sizes are usually sufficient. Some woodwork requires only two runs – a coarse sanding and fine sanding. 
• Hold the sander by the neck for a firmer grip with less pressure. If your orbital sander has a second handle, use it to better control the sander.
• Make sure to test the sandpaper (and the sander) on scrap wood first, to avoid any serious damage to your woodworking project. Once you are confident in your abilities and the type of sandpaper you have chosen, you can move on to sanding the wooden surfaces of your project.
• Try to keep most (two thirds) of the sanding disc on the surface at all times to avoid accidentally using the sander at an angle.
• Using sandpaper with a larger diameter can help you get more sanding done in a shorter time.
• Keep the sander moving throughout the sanding process to avoid over sanding that will result in an uneven finish. 
• When you have finished sanding, use the same sandpaper pad to go over the entire surface manually for the smoothest finish.
• Don’t skimp on those sandpaper discs! The cheaper varieties usually have a less uniform layer of abrasive material. They are likely to leave scratches, and in the long run fixing those scratches will prove more costly. 
• Use heavy anti-vibration gloves to avoid the lingering vibrations you might feel after using power tools. 

Using a random orbital sander is easy to learn, and it is a simple process. With this guide you have all the knowledge needed to start experimenting with a new sander. It can be used to sand any wooden surface, and their high power gives you the freedom to use it for coarse sanding (removing chipped paint, molding, etc), or fine sanding (polishing and buffing wood before the final coat of paint or varnish).