Whether you are new to woodworking or have been at it for years, there is no doubt you have either been preached at or done the preaching on the topic of sanding with the grain. It is a commonly accepted word of advice you will find at all levels of woodworking. It is a known fact that sanding against the grain can cause deep cuts that will show through a stained project.
You are probably already ahead of me at this point as the title of this article tends to give it away. The question is this,
“So then, how do I sand with the grain while using an orbital sander?”.
This is a completely valid question because as an orbital sander rotates, the sandpaper is hitting the wood from every direction. So even if you move the orbital sander with the grain, the rotating sandpaper doesn’t care. It will still sand in a circle. The short answer to the question is this,
You can not sand with the grain of the wood while using a random orbital sander. This is because as the sander spins and orbits, the sandpaper travels in a circle, sanding the wood from all angles. However, sanding with a random orbital sander makes sanding with the grain irrelevant as the random orbiting action of the sander makes very small scratches in all directions, which eliminates patterns and are not visually detectable.
The main purpose of sanding with the grain of the wood is to prevent tear outs or deep scratches that will affect your final finish. The random orbital sander solves that then, correct? Well, not exactly.
Just because an orbital sander ignores sanding with the grain doesn’t mean that you are home free. There are still best practices, tips, and issues that can arise while using a random orbital sander. Keep reading as we look more into this topic; you might just find some helpful information along the way.
Should You Still Move the Orbital Sander With the Grain?
A fairly common follow-up question is “Should I still move the sander along the grain?”. This is where a lot of opinions tend to come into play. A quick search on Google will come back with a whole array of sanding techniques.
Some people say to always go with the grain, even if you are using a random orbital sander. Others say they move the sander against the grain, then diagonal to the grain, and finally with the grain on their final pass.
This is the option I like the best, not because it is superior in sanding, but because it is a methodical approach to make sure the entire surface has been sanded evenly.
So which technique is the correct technique?
In my opinion, since the random orbital sander is designed to sand in all directions, it does not matter which direction you move it. The sandpaper will still rotate and hit the wood from all angles no matter which direction the sander moves.
However, if you are in doubt or still have questions, the best bet would be to play it safe and go with the grain. Just make sure you cover the surface completely and evenly as you sand.
Final Pass Hand Sanding
Another approach a lot of people tend to take when using an orbital sander, is to make the final sanding pass by hand. What this will do for you is it will help eliminate any swirl marks left over by the orbital sander.
In theory, the random orbital sander shouldn’t leave any marks behind but there are a ton of reasons that this can happen, even against your strongest efforts. Some of the most common culprits are improper sanding techniques or swirls from a clogged sanding disc.
The issue is that these marks tend to blend in well at the sanding stage and are not noticed. However, these cuts and swirl marks stand out like a sore thumb when the stain is applied.
This scenario is all too common. You finish sanding your project, and you are ecstatic about the results. You apply your first coat of stain and BOOM! Your great-looking project is riddled with cuts and unnatural marks all over the surface.
This is where hand sanding after doing the bulk of sanding with your orbital sander can help. After you finish sanding with your orbital sander, you can use some of the same grit sandpaper, but sand by hand and with the grain. This can eliminate any marks left over by the orbital sander.
Sander Leaving Behind Swirl Marks? 3 Possible Causes with Solutions
Are you wanting to avoid hand sanding as a final pass, but can’t seem to fix the marks your sander leaves behind? These swirls or “pigtails” are a very common issue, caused by a wide range of factors.
Now I can’t provide you with a fool-proof method to prevent the swirl marks, but what I can do is give you some tips and things to watch for as you are sanding to help prevent them.
Clogged Sanding Disc
If your sanding disc is clogged with debris, it will travel with the sanding disc gouging the surface as you move the sander. Once you go to apply the stain, this deep groove or cut becomes highly noticeable.
You can correct this issue by checking your sanding disc often, and replacing it if there is any debris found in the disc.
Too Much Pressure
Applying too much downward pressure can also cause swirls to appear. Besides having negative effects on your motor and backing pad, if the pressure is applied unevenly, one side of the sander can dig into your workpiece causing an uneven surface that will show up during the finishing stage. Click here to see our other article on what too much pressure does to your orbital sanders backing pad.
The correct amount of pressure to be applied should consist of only the weight from the tool and your arm. This should apply plenty of pressure to the orbital sander.
Speed Too Fast
Your random orbital sander is spinning and orbiting at the same time. Moving the sander across the workpiece too fast will not allow the sanding disc to make as many passes as it needs to. When this happens, instead of having tiny scratches that alternate in different directions, you will have longer scratches that are more noticeable.
It is advised to travel at about 1″ per second to avoid moving too fast and producing swirl marks or pigtails.
Conclusion
A random orbital sander by definition can not sand with the grain of the wood. You can however move the sander itself with the grain or in a particular pattern that you find works best.
Rather than being worried so much about going with the grain of the wood, it is better to focus more on proper sanding techniques to give your wood a nice, swirl-free finish. If you still can’t seem to get a nice finish because of swirl marks or pigtails, hand sanding as a final pass may be a good route to go.
