Brushless motors are becoming increasingly common in power tools, and for good reason. A typical brushed motor consists of wires, carbon brushes, a stator, an armature, and a commutator. Those carbon brushes constantly remain in contact with the armature – this creates friction (which accounts for the sparking that you see through the vent holes on a brushed drill) and heat. Both of these reduce the efficiency of the motor. The constant friction between the brushes and the commutator wear each other down, which adversely affects motor performance – and when a motor is subject to excessive heat build-up, it can lead to motor failure.

A brushless motor does away the brushes and the commutator. Instead, it uses an external electronic speed controller that creates the revolving magnetic field between the two magnets that causes the shaft to spin, producing torque. This reduces friction in the motor, which means less wear on internal components, and less heat build-up, resulting in a longer motor lifespan. Because the electrical connection is controlled digitally, rather than mechanically (by brushes), brushless motors run more efficiently, transferring more power to the drive shaft. Like brushed motors, they can heat up, particularly under a heavy load. However, they can be more effectively cooled. And, brushless motors are smaller and lighter, and virtually maintenance-free.

So, for the DEROS this means a smaller, stronger, more efficient motor that will last a lot longer.

The Mirka DEROS 550X comes with a Systainer 2 T-Loc – what is arguably the best power tool storage box on the market. Systainers are premium portable, stackable boxes designed to facilitate tool storage, transportation, and organization. They are virtually dustproof and waterproof. And yes, they’re the same Systainer that you get with Festool power tools, which means you can stack them together.

There are slots on the Systainer (two on the front, one on each side) in which you can insert cards to label the box contents, or business cards to identify ownership. A study handle with comfortably rounded edges folds flat against the top. One thing to note is the beveled corners, which makes it less likely to damage not only the box but more importantly walls, doors, or trim work when transporting and using your tools on-site.

The Systainer 2 has a huge amount of storage space, and the DEROS packs away neatly in the box, with lots of space to store a good assortment of sanding discs. There’s even room for a dust mask and hearing protectors.

One of the first things that struck me about the DEROS is it’s size – this is one compact (and light weight) sander. You can see in the photo above how it compares to the Bosch ROS65VC – the sander I’ve been using for the past five years. The Bosch is an excellent sander with some great features. But, at 5.3 pounds, it’s on the heavy side, which you really notice when using it for long periods of time, or when sanding vertical or overhead surfaces. While you can use it one-handed, because of it’s weight, and height (7-1/2″), it really wants to be held with two hands.

The 2 pound DEROS weighs about 60-percent less than the Bosch, and is a full 3-1/2″ lower in height. This more compact size is, in large part, due to the use of a brushless motor. In appearance, the DEROS is closer to a ‘low profile’ random orbital sander, such as the Porter Cable 390K and DeWalt D26456, though, curiously, both models have been discontinued. Which probably makes the DEROS the smallest, lightest ROS on the market.

The 3″ diameter handgrip atop the housing is nicely contoured, and has a soft rubber overmold that makes the DEROS very comfortable to use, and to control, whether with one or both hands. The fact that there is very little vibration means you can use this sander for hours on end and not end up with numb fingers or hands. I can imagine how much easier it would be sanding vertical surfaces with the DEROS

The DEROS doesn’t have a conventional speed trigger. Instead, it has a speed lever, similar to what you’ll often find on pneumatic tools. While not difficult to use, I did find that it took a few days before I felt comfortable with the lever.

I found that you could manipulate the speed lever either using a forefinger, or with the area of your palm just below your index finger. Which ever way you choose, you’ll probably want to turn the sander off whenever you’re not using it, as it’s fairly easy to inadvertently run the sander if you nudge the lever.

You can set the lever to operate in one of two ways – variable speed mode (the default), or maximum speed mode. You switch modes by holding down the ‘Decrease RPM’ and ‘Increase RPM’ buttons simultaneously – each time you do so the status light blinks red. In the default mode you adjust the speed by depressing the lever. As you do, speed increases from 4,000 to 10,000 RPM – the speed lever working just like a conventional variable speed trigger or your drill/driver or other power tool.

In ‘maximum speed mode’, the speed increases as you press the speed lever, up to a specified upper RPM limit. You set this upper limit by depressing the RPM buttons. Each time you depress the Increase RPM button, the upper RPM limit is increased by 1,000 RPM – up to a maximum of 10,000 RPM. To decrease the upper RPM limit you simply press the Decrease RPM button – once for each 1,000 RPM in speed. For example, if you set the upper RPM limit to 8,000 RPM (by pressing the Increase RPM button 4 times), then, as you press the speed level it will deliver variable speed from 4,000 up to a maximum of 8000 RPM.

While I tried both modes, I found it simpler to use the default speed mode. But, once you get the knack of it, switching between the two modes is a piece of cake.

As you’ll find on Festool power tools, the DEROS has a removable power cord. It ‘snaps’ into an outlet on the back of the sander. Unlike Festool, where you twist the two ends to ensure a tight connection, the DEROS uses a flexible ‘tab’ that engages a slot on the tool housing. I found that it worked quite well, even when pulling tightly I wasn’t able to dislodge the power cord. Being able to detach the cord makes it somewhat easier to store the sander in the Systainer. And, if you ever inadvertently damage the cord, it’s a snap to replace. And, the cord is a generous 14 feet long, which means you likely won’t have to bother with an extension cord.

Dust is the bane of woodworking. Happily, dust collection on the DEROS is superb. The 1″ dust port on the back of the sander accepts a standard 1-1/4″ dust hose. As you can see in the photos above, the DEROS connects snugly on either the Festool or Bosch hoses. A great feature is that the dust port on the DEROS swivels, which helps to keep the hose from fishtailing all over the place.

The backup pad can be removed and replaced if it becomes damaged. Just slip the supplied wrench under the pad and onto the retention nut, and turn the pad counterclockwise to remove it. The first time I tried this I had to exert quite a bit of force – thereafter, removing the pad was much easier.

Mirka recommends that you use a backing pad with it’s mesh sanding discs (see below). Should you find that vibration increases after mounting the pad, you can install a set of three screws and nuts to counteract this vibration. I tried using the DEROS both ways, and really didn’t notice any difference.

The DEROS comes with a variety of Mirka abrasives and a backing pad. If, like me, you haven’t used these abrasives you’re in for a real treat. You get three Abranet HD (Heavy Duty) sanding discs – one each of 40-, 60-, and 80-grit., six Abranet mesh sanding discs – one each of 80-, 100-, 120-, 150-, 180-, and 220-grit, and an Abranet protective backing pad. You place the hook & loop backing pad in between the sanders backup pad and the Abranet mesh discs. It reduces wear on the DEROS backing pad and helps improve dust collection air flow.

While these Abranet discs may look somewhat like a conventional paper-backed sanding disc, they’re entirely different. The substrate is made of a strong, flexible polyamide nylon fabric. It looks a lot like the material used on a screen door to keep the flies out of the house. Abrasive particles are bonded to the substrate.

The result is a sanding disc that I found cuts quickly at every grit level. I found that I could achieve a smooh surface faster with the Abranet discs, compared to the Norton discs I currently use. And, they seem to last a lot longer. However, it will take more extensive use of the discs to see how much of savings they offer. In any event, Abranet discs are not significantly more expensive than Norton discs, averaging 0.86¢ when purchased in bulk. Plus, they come in a wide range of grit sizes up to 1000-grit.

The zillions of holes in the disc, and the two dozen or so holes on the backup pad, make for excellent dust flow. Considerably better than any other ROS that I’ve used. On flat surfaces dust extraction approaches 100 percent.

I did find that the Abranet mesh discs are more easily torn than conventional paper backed discs, particular when removing the discs from the backing pad. You want to remove them with some care, and not overly aggressively.

I’ve been using the DEROS with the Abranet sanding discs, as well as with conventional sanding discs. Using either, the DEROS is one super sweet sander. It has very low vibration, runs quietly, is comfortable to hold, doesn’t heat up (based on a 60 minute sanding session), and the dust pickup is stellar. The speed lever does take some time to get used to, but it isn’t overly difficult.

I found that the DEROS 350 watt motor maintained consistent speed regardless of the disc grit I used, the material I was sanding, or the rotational speed of the sander.

The DEROS is not likely to be the choice of hobbyist woodworkers or DIYers, but for professional woodworkers and finish carpenters – those who do a fair amount of sanding and want the job done quickly and efficiently – the benefits will certainly justify the investment.