What Is a DA (Dual Action) Sander and What Is It Used For?

The right sander for a project will vary on a case-by-case basis, but a DA (dual action) sander tends to do an excellent job when you have to sand and buff at the same time. So what is a DA sander, and how is it used?

A dual-action (DA) sander is a tool that combines the best functions of disk and belt sanders. DA sanders are powerful and versatile and are used for sanding and buffing. Dual Action sanders move backward and forward, copying the linear action of a belt sander, but are also slightly rotary.

Many woodworkers rely on a DA sander a great deal. The rest of this article will go into a bit more detail, highlighting everything you need to know about this tool and why you should have it in your shed.

What Is a DA Sander?

To understand a DA sander, you have to first look at the two sanders it is loosely based on, which are the belt sander and the disk sander.

Belt sanders are designed to run a sandpaper belt at high speeds, scraping away lots of material quickly. They are useful when you’re removing high bumps on flat surfaces. However, they are often too powerful, removing too much material or leaving scratches if you don’t work gently.

The disk sander design is such that it spins a disk of sandpaper in a circle at high speeds, which allows it to sand uneven materials using the edge of the disk.

Some disk sanders have a typical wobble in their movement, ensuring the sander doesn’t dig too much into the surface you’re sanding. However, this doesn’t prevent scratches across the grain while working on wood.

Now, DA sanders combine the best of both sanders we’ve seen above. The sandpaper pad on these also moves in the linear backward and straightforward movement of the belt sander, but there’s also the slightly wobbly or circular motion of the disk sander. The movement is rotary most of the time, but it can also look randomly orbital.

The dual-action mechanism on a DA sander may vary from one product to another (source: Ehow).

In some, the sandpaper may appear circular and spin like the disk sander. In others, it can be rectangular, moving in a semi-rotary motion where the paper doesn’t turn while working.

DA sander on plank

How Does a DA Sander Work?

A DA sander comes with two modes:

The first mode locks the sanding pad into spinning in a flat-plane circle.

Turning on the second mode will move the pad using an internal bearing.

This delivers the wobbly movement, which allows it to work without creating excess friction against the surface.

The dual-action nature of a DA sander gives you more options for completing your sanding projects. You can use the locked rotation function when you need to clear some materials fast. The wobbly or orbital motion works well for creating a smooth finish.

The polishing action or sanding disc on a DA sander is connected to a motor system that spins via a gear system.

The motor is responsible for the movement, you see. The sander design allows it to cover large areas of any surface you’re working on quickly.

The sanding wheel also doesn’t dwell too long on a specific portion of the surface you’re working on, which helps prevent over-polishing or sanding of the area. This helps to deliver a better finish overall.

The composition of the tool allows one-click switching from sanding to buffing a surface.

dual action sander on furniture

What Is a DA Sander Used For?

Since DA sanders don’t leave scratches and are easier to control, DA sanders are commonly used for:

  • Sanding wood surfaces when you want to create a super-smooth outward appearance.
  • Smoothing out a surface without leaving any marks (as long as you use the tool correctly)
  • On multiple wood pieces with different grain directions at the same time
  • Used by pro woodworkers or carpenters on intricate woodworking projects
  • Used in auto body repair shops – for example, to remove old paint from a car’s bodywork before a respray

What’s the Difference Between a DA Sander and an Orbital Sander?

The major difference between a DA and an orbital sander is how the sanding pad moves.

An orbital sander can only move in circles, while the DA sander can move in circles and back and forth.

A DA sander may be grouped under the orbital sander section on some online shops. This isn’t quite correct – you should look for the “Dual Action” distinction if you’re in the market for a DA sander.

To help you out, I’ve put together a shortlist of the best DA sanders on the market right now.

DA sander used on wood

How Do You Use a DA Sander?

To use a DA sander, here’s what you should do:

  • Set the machine up properly in line with the user instructions.
  • While it is turned off, place the sandpaper plate on the surface you’re working on.
  • Switch the machine on while it’s on the surface, and turn it off when you remove it from the surface. Starting the DA sander before placing it onto the surface can leave strong scratches on the surface you’re working on. Similarly, you’ll get swirl marks if you stop the sander while it’s still on the surface you’re working on. This is due to the slow RPM (Revolutions per Minute).
  • Ensure the pad is flat on the surface while working, as any slight tilting can reduce the rotation speed and make the tool move in a single orbital motion. You’ll get swirl marks if you work with the machine tilted.
  • Exercise caution as you near the edge of surfaces as tipping the sander around these areas will lead to sharp cuts around the edges.
  • Every new run on the surface should overlap the last one by 30-50% without lifting the machine.
  • You don’t need to exert too much pressure when using a DA sander. The machine’s weight is usually enough for proper sanding in many cases, but if you’ve bought one of the lighter-weight models, you can put a little pressure on it while working.
  • Excess pressure on the sander while working will make it stall or slow down. The abrasive will leave swirl marks that will be visible after staining or finishing in this scenario. Consistently applying excess pressure on the machine while working will also damage the bearing.
  • The best way to sand with this tool is to start with an up and down motion and end with a left to right motion.
  • Don’t hold the sander down on a portion of the surface and apply pressure as you’ll get swirl marks.
  • Change the abrasive as soon as it starts to show signs of wear. A good way to check for this is to make some pencil marks on the surface you’d like to sand and run the DA sander over it. If it doesn’t remove the pencil marks quickly, it’s time to change the abrasive.
  • Connect a vacuum to the DA sander to trap dust cleanly. This will reduce the quantity of dust the abrasive has to wade through, prolonging its lifespan.
  • Don’t forget to wear protective gear when working with a DA sander. You need a mask as inhaling dust from sanding is dangerous. You should also protect your eyes and ears for the best results. For this, check my list of the best masks for woodworkers, and the best safety goggles.

Can I Use a DA Sander for Polishing?

You can use a DA sander for polishing. However, you’ll need to go with models that have variable speeds and also get a selection of polishing pads (source: Eastwood).

Your skill level, practical experience, and the level of pressure you apply to the sander are all factors that can influence the result you’ll achieve after polishing the surface.

What Size Air Compressor Do DA Sanders Use?

A typical DA sander will use a 3 HP compressor. They also usually require 11 to 13 CFM (cubic feet per minute) (Source: Quincy)

These are features you should pay attention to when purchasing your DA sander, and most manufacturers will include these in the list of features on the product page or the user manual.

Confirm the power of the tool to ensure it can serve in the use cases you’ve got in mind.

If you need an expert view on what the best DA sanders are for the job you have in mind, take a look at my top DA sanders article. I love my dual action sander, and it’s an essential part of my kit. After reading this, I hope you can see why!