Greg Paolini: Curing Sander Swirl Marks

Tuesday, September 27, 2011 | Reader Comments | Dust Extractors | Sanders

Greg Paolini


In this article, Gregory Paolini shares a story about one of his students and why they were getting swirl marks while sanding. Gregory Paolini is a nationally recognized woodworker, author, and woodworking instructor.  You can learn more about him by visiting his website at

I recently worked with a student, who we'll call Rick for the sake of this conversation.  Rick was enrolled in one of my finishing classes, and when we began to talk about surface preparation, Rick stated he was doing all the right things – Everything I recommended, but he still ended up with sanding swirls in his work.

In this case, proper surface preparation began with outfitting his random orbit sander with 100 grit sand paper.  Then Rick let the weight of the sander do the work, applying no additional downward pressure.  Then Rick moved the sander along the board at about one inch per second.  And as he finished one pass, he reversed direction, and overlapped the previous pass by about half the width of the sanding pad.  Everything sounded really good to me so far.  Then Rick told me "I even use a shop vacuum hooked up to the sander to make sure I remove all the dust and loose sanding abrasive particulates, but I still get swirl marks".
And that was the key to Rick‘s dilemma.  Shop vacuums are great for cleaning up a shop, but they're not really made for the dust created while sanding - Their filters just clog up too quickly from the fine particles, even if you use one of the aftermarket ultra-fine filters.   But the bigger problem is, shop vacuums aren't made to be used with sanders.   Sure you can hook one up to a sander.  And a shop vacuum will remove all the dust, debris, and loose grit while working.  But a shop vacuum isn't designed to work with a sander, and therein lies the source of Rick's swirl marks.

A shop vacuum creates a lot of suction.  So much suction in fact, that it actually sucks the sander down against the work piece while sanding.  How is this any different from applying downward pressure to the sander by hand?  Whether you're pushing down on a sander, or a vacuum is pulling it down, the end result is simply increased sanding pressure, which of course results in sanding swirls.

I showed Rick the step-less adjustable suction control on our Festool CT HEPA Dust Extractors, which we use in various phases of most of our woodworking classes.  The step-less control allows you to precisely adjust how much, or how little suction is required for the task at hand, and literally dial it in.  So if you're using a router which generates a lot of wood chips and dust, you can crank up the suction to get every last bit of power required for the task.  And if you're sanding, you can lower the suction to the precise point where all of the dust is extracted, but no unnecessary downward pressure is applied to the sander, virtually eliminating unwanted sanding swirls. 

Step-less suction control is just one of many great features on the Festool CT series Dust Extractors.  And thanks to this feature, Rick no longer has to deal with sanding swirls, as he is a proud owner of a new Festool CT 26 Dust Extractor.

Take advantage of our Fall 2011 Sander Promotion to save 10% instantly on a phenomenal Festool sander during October and November 2011. Bundle it with a Festool CT Dust Extractor and save 10% off the price of the dust extractor, only available in the United States at participating Festool dealers, and save yourself from the struggle with sanding swirl marks.

So, to avoid swirl marks...

  • Choose the right abrasive. Festool has an exceptional selection of task-specific abrasives to help you get optimal results with minimal effort. Our new Granat abrasive is going to be the most versatile while offering a long-lasting cut without clogging. Check out the abrasives guide on our website for more information about which abrasive is best for your application.
  • Choose the right grit for the task at hand. For instance, don't put 320 grit paper on your sander and then bear down on it with your full weight to remove thick coats of paint.
  • Always use dust extraction. Failure to use dust extraction when sanding allows the dust, debris and grit from the abrasive to be constantly ground back into the material. As you progress through the grits, large particles from the previous pass are still on the surface and work against your efforts for that perfect finish.
  • Reduce the suction on your Festool CT HEPA Dust Extractor so that the sander feels like it's floating on the surface of the material. If the suction is too high, it will pull the sander into the material and make it more difficult to move and will increase swirl marks. Always use

A special thanks to Greg for sharing this story with us.

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