When sanding timber, another tool in your finishing arsenal is the variable speed control on your random orbital sander.

When I’m talking to clients who are looking at buying a sander, one of the things I’ll talk about very early in the discussion is the benefit of speed control when sanding.
The main points that you need to remember are, the coarser the paper the higher the speed; the finer the paper, the slower the speed.

Coarse paper on slow speed tends to dig in and ‘bite’ the work, which can lead to scratches, and swirls, which are bloody hard to get out. Coarse paper on high speed tends to ‘skim’ over the work and while it may take a little longer you’ll achieve a more controlled result.

Fine paper at full  speed  “floats” over the surface requiring more pressure to achieve any result, and more pressure increases the risk of swirl marks.  Fine paper at slow speed has even contact with the work piece and requires minimal pressure to achieve a top result.

When you start sanding and are using, for instance a 40 or  60-grit paper,  start with the sander on speed 6.  As you start moving into progressively finer grades, gradually begin to lower the sander speed. Use the chart below as a rough guide for sander speed related to sanding grit.

Sanding grit.     Speed
40.                       6
60.                        6
80.                       6
120.                       5
150.                       5
180.                       5
240.                       4
320.                      4
400.                      3
500.                       3
800.                       2
1000.                     2
1200.                    1
1500 & finer           1

This chart is a suggested range only and results can vary depending on the type of timber that you choose and the mechanics of your sander.

 (150mm diameter abrasives up to  4000 grit are available from  most Festool dealers. Papers listed here are from the Brilliant 2 and the Titan range.)

The transition point when sanding is 400-grit.

This is the stage where you stop sanding the timber and start burnishing it. From 400 up you’ll start to see the surface of the timber develop and become smoother with every sanding stage that you complete.

 Don’t forget to feel the timber as you sand it so that you become more familiar with how each sanding grade contributes to the overall finish if the surface.   When you reach 1200 grit, you should see the timber surface begin to develop a lovely lustre and the surface will begin to shine. This happens, because the flour, (really, really fine sawdust) which is created by the super fine grits that we have been using is filling and closing the pore of the wood, burnishing the surface and giving us this glass like finish.

As an exercise, try using this method on different species of timbers to see how their various surfaces develop. I’ve used this method on both hard and softwoods with consistently good results
Jump in and have a go at this sanding method.  There are many ways to finish and use your sander and what I’ve discussed here is the method that works for me.

Drop me an email if there’s and areas you need clarification on or, let me know how you found this method.