# ROS swirl marks



## Rhaugle (May 12, 2017)

Hi guys,
ive got a bosch random orbit sander and im getting a lot of swirl marks. Some of them are real bad and i cant get them out..

I need some tips on these sanders so this doesnt happen anymore.. Am I putting to much downward pressure on the sander and thats whats causing this? Maybe I'm a little to impatient with sanding? Its very annoying!


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## Steve Neul (Sep 2, 2011)

It sounds like you are using too coarse sandpaper. Sanding is a process which if you need to start with a coarse paper you need to come back and gradually sand again with finer and finer paper until you get to around 180 grit. If you jump from a coarse paper to a too fine one it may not remove the scratches made by the coarse paper. It also helps when sanding to wet the wood and raise the grain between grit changes. This will make sanding more effective.


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## shoot summ (Feb 21, 2014)

I'm with Steve on this one, first thing would be your paper is too coarse.

Beyond that it could be a malfunctioning sander. Does the sander appear to really be RO, or is it spinning? Are you starting and stopping the sander on the work piece? Some of these sanders will spin when they are not in contact with the work piece.


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## epicfail48 (Mar 27, 2014)

TOo much downward pressure could be an issue, another is moving the sander too fast. Let the weight of the sander do the work, dont move along the work too fast. A good movement rate is about an inch per second


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## Rhaugle (May 12, 2017)

I usually start with 80 (if I have glue to clean up), then 120, 180, 220 finish


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## shoot summ (Feb 21, 2014)

Rhaugle said:


> I usually start with 80 (if I have glue to clean up), then 120, 180, 220 finish


80 is coarse, I rarely go below 100 unless I am trying to remove a lot of material for some reason. Try scraping the glue instead?


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## Leo G (Oct 16, 2006)

Sanding is simple, just like people say anyone can paint....

Starting at 80 is fine as long as you progress through the grits and eliminate any scratches left by the previous grit.

Two things. You are probably pushing down to hard. I don't agree with the people that say let the weight of the sander do the work. If you have all the time in the world that's the way to go. But I like to get things done. 3-4 lbs of pressure is good. You shouldn't be changing the RPM of the sander when you press down. You need to keep the sander flat, leaning it to one side sands quicker, but introduces swirl marks.

Dust extraction. You need it. It will prolong the sandpaper life and it will keep swirls down.

Good sandpaper You need it. Cheap sandpaper will drop of bits of grit and they roll around under the sander and cause marks. Dust extraction will suck these up and prevent most of the damage they can do.

Generally sand in a circular motion. Don't go to quick. Overlap your circles by 50%. That means the sander hits the spot twice as you go across your project.

It's possible it's just the sander. Could be worn out, bad pad, loose bearings. Try another sander if you can and see how that differs.


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## Quickstep (Apr 10, 2012)

I've gotten swirl marks when using cheap sandpaper. Either a chunk of grit gets loose like Leo said, or the grit on the sheet isn't consistent.




To Leo's other point, dust extraction makes an amazing amount of difference. Not only does it keep the dust out of the air, it gets the dust off the board so you're not re-sanding dust.


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## Brian T. (Dec 19, 2012)

It's next to impossible to build a sandpaper with uniform grit size. What you read is the "nominal" particle size.
They admit that there will be bigger and smaller grit particles on the sheet. Most of them are ***.

I think that the situation improves a lot when you go above 800, into the 3M fine automotive W&D finishing papers.
Not only is the grit more uniform but the quality of the binder is far better to hold the grit on the sheet.
The price jumps because of the quality control. I use up to 2,000 for sharpening wood carving tools.

I've never liked the idea of trying to finish wood with a ROS. 
The stroke is bound to cross-cut and shred some wood fiber.
Look into cabinet scrapers. Make a few, buy a few, they're cheap. 
They cut & shave the wood, you need a magnifying glass to see it.
That isn't shredded, it is seriously smooth.

Made some from lumber strapping band steel. I thought they made dust.
The cutest little curly shavings you ever did see.


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## JCCLARK (Jan 30, 2007)

The most common culprit is moving the sander to fast,
like you see them do on TV.
You have to move a R.O.S. slowly, like the instructions say.
You can't go back and forth as quickly as hand sanding with a block.


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## sanvito (Feb 26, 2018)

had same issue from cheap LOWES sandpaper for my Makita orbitor. The 5 holes did not line up properly.

I replaced it with MIRKA assortment pack. No issues.


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