Swirls from ROS

[bdk5]

I've noticed on occasion after using my ROS that a distinct, single line of swirls appears on my wood, as if a single piece of grit stands proud of the rest of the sanding disk and marks the wood. What am I doing wrong? The only guess I have is that I may be over-using the particular piece of paper and the marks are the result of a small rip, fold, or crease in the paper that is causing the mark. Any ideas?
Thanks,
Bryan

[Tom Slick]

what grit and are you using a vaccuum?

[poolhound]

Do you throughly clean the workpiece after changing grits? if you dont you risk adding left over grit on the work to the finer grits and the result would be as you describe.

[cabinetman]

Good questions on your procedure so far. It could be a piece (some grit) of the sandpaper that gets dislodged. Sandpaper (especially aluminum oxide and garnet) that has been damp or subjected to moisture or high humidity loses some of its togetherness, and can self destruct, or just start falling apart.

Keeping the area clean, and as stated using a vac can help. Keep an eye on the sanding process so as not to get too far with an ongoing problem
.

[LarryG]

Are you using good quality paper? I use Harbor Freight's sanding sponges for surfaces that don't matter, like knocking the feathers off the concealed side of a cut. They're dirt cheap but the grit sizes aren't as consistent as the better brands. On my ROS I've mostly been using Mirka paper, with excellent results.

Check the pad on the sander, to make sure there's not something there that could be telegraphing through the paper.

[bdk5]

I use Mirka paper and a vacuum. I haven't noticed which grit I've been using when the problem occurs (I typically don't notice until later), but given the responses, I suspect my problem is the failure to thoroughly clean the surface between grits. The pattern I see is entirely consistent with some particles from a prior grit remaining on the surface. I will try to do a better job cleaning between grits--hopefully that will solve the problem. I don't know why the thought never occurred to me. Thanks.

[poolhound]

I will try to do a better job cleaning between grits--hopefully that will solve the problem. I don't know why the thought never occurred to me. Thanks.

My planer does a great job so in most cases I dont need to start with really coarse grits. Either way the amount of inter grit cleaning I do is in direct proportion to the importance of the surface e.g inside and hidden or main front exterior.

I always clean after sanding with any grit but if its an important surface I will first vacuum and or use compreesed air. I make sure I clean the workpiece, benchtop and sander and then use a tack cloth to make sure I dont leave any sanding dust or grit on the work before using the next grit.

[Tom Slick]

"too much" vacuum has been known to pull the sander down too tight against the work piece and leave swirls. do you get swirls with higher grits like 220-320?

[pecker]

I got those marks once when I used a coarse grit, 80 I think, but have never seen it happen with 100 or higher. Maybe the larger abrasive is more prone to breaking off and getting dragged around by the sander.

[AusRob]

Hi,
My gut says adjust the vacuum, but maybe you could look at the particular species of timber it's happening with. Some are more susceptible to swirlies than others in my limited experience.

Regards,

Rob

[Popeye]

No one has mentioned it yet but.... if I'm not careful putting the running sander down on the work I've gotten a swirl that didn't get noticed while sanding that grit. I can get the swirl no matter what grit I'm using. When I get close to the end I start the sander when it's in contact with the work and at slow speed. Pat

[jabe]

Proper way to use a ROS is to put it on the work surface before starting. Do not use downward pressure, the weight of the sander is enough pressure and move the sander at a moderate steady speed with the direction of the wood grain. Leave the sander on the work surface when you turn it off but move it till it slows down enought to lift it off the work surface safely. Clean the work surface and sanding pad before sanding with another grit of sandpaper. This is how I taught my high school students and we never had swirling issues if they followed these procedures. All of the ROS in the shop did not have any vacuum attached to it. But I would also check your sanding discs and sander pad for any defects if you're following all of the above procedures. Hope this helps.

[TheRic]

Make sure the surface you are setting the sander down on, when not in use is clean. You might be picking up something there, I know it has happened to me.

[poolhound]

Make sure the surface you are setting the sander down on, when not in use is clean. You might be picking up something there, I know it has happened to me.

Good point Ric,

you could try one of these

http://www.sandersitter.com/