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In this article, I show you how to sand rough wood to a smooth surface with a swirl-free sanding technique. Also, I show you how to fix sanding mistakes the easy way

This sanding technique consistently produces a smooth wood surface on live edge wood slabs & rough cut lumber with no swirl marks or pigtails.
So, let’s dive in with a list of tools to make the sanding job easier.

Tools and Material

Rotex Sander
40 grit Sandpaper
60 grit Sandpaper
80 grit Sandpaper
120 grit Sandpaper
150 grit Sandpaper
180 grit Sandpaper
220 grit Sandpaper
320 grit Sandpaper
HEPA Vacuum

Full Video Tutorial

Even if you don’t sand wood, the techniques covered in this project can be directly translated toward refinishing any wood surface.
There are several things that will be difficult to explain with words and images, so be sure to check out the video below!

The Secret Sauce

Do you want to know the secret sauce to sanding?
Of course you do, that’s why you are reading this article.  Here are the ingredients to the Sauce:

  1. Quality Sander and Sandpaper
  2. Dust Extraction
  3. Proper Sanding Technique

If you have #1 and #2 and use #3, you will get perfect results each and every time.
One other important point: If you can’t buy a sander or dust extraction system, I recommend borrowing one from a friend or renting one if possible. Using quality tools saves you time, frustration, and produces great results.

Sand Like a Boss (or Pro)

Keep in mind, I wrote this DIY article to show you how to sand ‘Like a Boss’ and that is exactly what I intend to do.
As a result, the tools I used may be a bit expensive for the normal weekend warrior.
With that said, let me be clear, you do NOT need an expensive sander to achieve great results.
A normal belt sander or orbital sander will work just fine, but it may take more time, patience, and elbow grease.

Best Sander for Rough Wood Slabs

There is a quote that states something like, “The skill lies within the craftsman, not the tool.”
While this is true most of the time, it is not entirely true for wood sanding – in my opinion.
However, let’s face the facts.
Most people, including myself, don’t enjoy sanding wood.
It is monotonous, boring, time consuming, and severely disappointing when the surface contains swirl marks or pigtails.
However, wood sanding can be an enjoyable experience.

Festool Rotex 125

I use the Festool Rotex 125 sander along with a dust extractor for all wood sanding jobs.
While I realize the price tag for these items exceed most budgets (including mine), the versatility of this sander make it worth it.

best sander for rough wood slabs - festool ro125

“Buy once, cry once” reigns true regarding a wood sander and dust extraction system.

The rotex 125 has 2 modes (dual mode):

  1. Rotary Mode for aggressive removal of stock.
  2. Random Orbit Mode for a fine finish.
Festool RO125 Rotary Mode
festool RO125 random orbit mode

Also, this sander can polish with the a polishing pad and sponge in rotary mode.

Essentially, this sander plays the role of a belt sander (but much better) for aggressive removal of stock in rotary mode.
Also, it is a random orbit sander for a smooth finish while in random orbit mode.
I use both of these modes when sanding rough wood slabs or lumber.

How to Sand Rough Wood

While the sander does the majority of the heavy lifting, there is a grit sequence combined with a sanding mode and a proper technique.

Grit Sequence

First, sanding grits play a vital role in wood sanding. So, do yourself a solid and don’t skip sanding grits!

The sanding mode along with my grit sequence is as follows:

  1. In Rotary Mode
    1. 40 grit
    2. 60 grit
    3. 80 grit
    4. 100 grit
    5. 120 grit
  2. In Random Orbit Mode
    1. 120 grit
    2. 150 grit
    3. 180 grit
    4. 220 grit
    5. 320 grit

Also, I use the highest speed setting throughout the entire process.

Wood Sanding Technique

First, always work in 2′ x 2′ sections at a time.
This makes it easy to monitor for mistakes and quickly pivot to correct them if needed.
Place the sander on the surface and turn it on.
Don’t turn it on then place it on the surface – no need to make a mistake on the very first movement. :)

Swirl Free Sanding Technique

Next, sand horizontally across the wood grain and overlap the lines by 1/3 or 33%.

Swirl Free Sanding Technique

Then, sand vertically with the wood grain and overlap the lines by 1/3 or 33%.

Swirl Free Sanding Technique

Finally, sand in a circular pattern of roughly 8″.

wood sanding technique

Repeat this technique for each and every grit.

How to Fix Sanding Mistakes

Even though I own an awesome sander, dust extraction system, and use quality sandpaper – I lose focus.
At times, I lose focus while listening to the JRE podcast, put too much pressure on the sander, and cause a swirl mark and/or pigtail.
I tell myself, “No need to worry! It’s an easy fix as long as I follow the Golden Rule of Sanding.

A wood sanding mistake, such as a swirl mark or pigtail, can only be removed by the sanding grit from which It was formed.

Pahjo Designs – The Woodworking School of Hard Knocks

Quick Tip: Read the golden rule one more time before proceeding – maybe even twice or 3 times.

Monitor for Mistakes

In order to fix sanding mistakes, I inspect the wood surface after each grit.
If I see sanding mistakes, I sand with the same grit again.
Most of the time, this fixes the sanding mistake.
If not, I continue to back down grits until I fix the sanding mistake.

Fixing Sanding Mistakes – An Example

For example, I sand with 120 grit sandpaper and notice a few swirl marks.
Since I know 150 grit will not remove the swirl marks, I sand with 120 grit again (from reading the golden rule).

120 grit sandpaper

After I sand with 120 grit for the second time, I still notice the swirl mark.
So, I sand with 100 grit sandpaper (b/c I read the golden rule twice).

100 grit sandpaper

When I finish sanding with 100 grit, I still notice the swirl marks.
As a result, I sand again with 80 grit sandpaper (b/c I read the golden rule 3 times).

80 grit sandpaper

Finally, the swirl marks are gone with 80 grit sandpaper.
Since I removed the swirl marks with 80 grit sandpaper, I know they were caused by 80 grit sandpaper.
Obviously, I did not inspect the wood for swirl marks after sanding with 80 grit the first time.

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    Conclusion

    I hope this article on how to sand rough wood slabs and swirl free sanding tips help you on your next project.

    Swirl Free Sanding Technique

    Time needed: 2 hours.

    How To Sand Rough Wood Slab

    1. Gather Tools

      I recommend the festool rotex 125 or 150 sander, a festool dust extractor, and the following sandpaper grits: 40, 60, 80, 100, 120, 150, 180, 220, 320.

      best sander for rough wood slabs - festool ro125

    2. Set Sander Mode and Speed

      Next, place the Rotex 125 in rotary mode on the highest speed setting with the black sanding pad that came with the sander.

      Festool RO125 Rotary Mode

    3. Sanding Technique – 40 Grit through 120 Grit

      In order to sand rough cut wood slabs, start with 40 grit sandpaper and work in 2 foot by 2 foot sections. First, sand horizontally across the wood grain. Next, sand vertically with the grain. Then, sand in a 1 foot circular pattern with the grain. Repeat this step for the following grits on the entire surface: 40, 60, 80, 100, and 120 grits.

      Swirl Free Sanding Technique

    4. Monitor Swirl Marks and Pigtails

      While sanding rough wood, monitor swirl marks and pigtails after each grit. If swirl marks and pigtails appear, sand with the previous grit again. Remember, higher grit sandpaper will not remove swirl marks or pigtails caused by a previous grit.Swirl Free Sanding Technique

    5. Switch to Random Orbit Mode

      Switch the Festool Rotex 125 to random orbit mode and leave it on the highest speed setting.

      Festool Rotex 125 Random Orbit Mode

    6. Sanding Grit Sequence

      Using the same sanding technique, sand the wood surface with the following grits: 120, 150, 180, 220, and 320 grit. Using the same sanding technique, sand the wood surface with the following grits: 120, 150, 180, 220, and 320 grit.

      swirl free sanding technique

    7. Switch Sanding Pad & Lower Speed

      Switch the sanding pad on the Festool Rotex 125 sander to a soft sanding pad and lower the speed setting to half. The soft sanding pad prevents the sander from changing the natural shape and contour.

      Festool Rotex 125 soft sanding pad to remove bark from live edge

    8. Remove Bark From Live Edge

      To remove bark from live edge, lightly go over the live edge with the sander.

      remove bark from live edge

    Frequently Asked Questions

    What is the proper way to sand wood?

    The proper way to sand wood is to start sanding with a sanding grit coarse enough to remove the debris and expose the wood grain. Then, sand with a slightly higher grit to remove the scratches caused by the coarse grit. Repeat this process until you reach 220 grit.

    Swirl Free Sanding Technique

    What is the best sandpaper for wood?

    The best sandpaper for wood is Festool Granat, which is comprised of hardened Aluminum Oxide, Synthetic Resin, and Closed Coated.

    120 grit sandpaper

    What causes sanding swirls?

    Sanding swirls are caused by debris getting stuck between the sandpaper and the wood surface. Also, sanding swirls are caused by applying too much pressure to the sander which traps debris between the sandpaper and wood surface.

    Swirl Free Sanding Technique