Random Orbit Sanders

A standard 3/8" pneumatic drill with a foam sanding
mandrel makes a great tool for power sanding

Random Orbit Sanders - Overview: Most woodturners would agree that sanding is one of the least desirable parts of the woodturning experience. Thankfully, new tools like improved pneumatic sanders, as well as high-tech abrasives have become available in the last few years that make sanding not only easier, but faster as well. Almost any electric or pneumatic drill can be outfitted with a foam-backed sanding mandrel and a hook and loop abrasive disk for a cost effective and simple sanding solution.

For years, this is how I sanded my faceplate projects and hollow forms. In the early days of my studio, I used electric drills with foam sanding mandrels and either sticky backed, or hook and loop backed abrasives. This approach worked well enough initially, but as the volume of my business grew, I quickly found out that few electric drills were up to the task of prolonged use.

Using a Sioux Dual Action sander to finish
sand a natural edge Honey Mesquite platter

After I burned up five new electric drills over the course of one summer, I switched to pneumatic drills for all of my sanding. While the move to pneumatics eliminated my failure problems with electric drills, I was still limited to rotary action when sanding. While rotary sanding is a great choice for many sanding tasks, it is far from ideal for others.


Quest for a New Finish Sanding Solution

Like so many things in life, there is no single tool, protocol, or product that is best at everything. As my studio continued its growth, I began to experiment with other tools to sand my projects including passive (inertia) sanders, ultra high-speed sanders (15,000 RPM Right Angle Grinders), giant electric rotary sanders with 5" and 6" disk heads, random orbit sanders (also known as "DA" sanders) and numerous versions of similar tools that were pneumatically powered.

Dynabrade's pneumatic palm sander features a
3" Velcro-faced sanding pad and a 3/16" orbit

When the dust had settled, I found out that Random Orbit Sanders (ROS) offered the extra performance I was looking for when my rotary tools fell short. Very few woodturners I've met through the years use random orbit sanders in their studios. When asked why, most say they're too expensive, they don't work well and can be cumbersome to use on smaller projects. While I would agree that ROS can be a wee bit expensive, they can be very useful in certain sanding situations.

Most of the bad rap that random orbit sanders get comes from the fact that they will stop if you press to hard on the pad whilst sanding. Random orbit sanders do not turn the abrasive pad only in a circle like a standard rotary drill; rather they spin the pad as the pad moves in an eccentric orbit. This simultaneous spinning and oscillation creates a very effective sanding action. However, if you are a bit heavy handed the pad will simply stop, whereas a rotary sanding tool like an electric drill will slow a bit, but keep on running.

However, when you're working with the finer abrasive grits (P400, P600, P800 etc.), the dual action of a ROS produces a more uniformly sanded surface than a typical rotary tool. This is especially true when sanding inlaid crushed stone, sanding across metal band inlays, sanding timbers that feature significant differences in the density between early wood and late wood, or when sanding spalted timbers with a highly variable structural density to name a few.

The key to using random orbit sanders is to think of them as a final finishing tool, not a primary sanding solution. If you keep a light touch and limit the ROS to the final finishing grits only, a ROS can produce superb results.


Random Orbit Sanders for Woodturners

AirVantage's 5" random orbit palm sander is an
excellent choice for medium to large size projects

One of the criticisms I've heard about ROS is that they are just too large for the average turned bowl or platter. In the past, many ROS featured pads that were 5" or 6" in diameter, which severely limited their use in the average woodturner's studio. However, in recent years small palm sized ROS sanders have become available that feature 2" and 3" Velcro faced sanding pads. There are even a few models with 1.5" pads, so pad size is no longer an issue.

Another complaint I've heard is that the size of the random orbit sanders is too large for smaller projects typically turned on lathes. While it is true that older ROS had orbits that were better suited to flatwork projects, newer ROS have orbits as small as 3/32," which is about half the orbit size of a typical ROS. This means the size of the orbit is also no longer an issue.

Grex's Dual Action sander features a very
powerful motor with a 2" Velcro-faced sanding pad

The last complaint I've heard is that ROS are too expensive. Some models do indeed have prices that hover in the stratosphere, but there are some affordable models as well. Newer palm sized models are easy to use and comfortable in your hand. The smaller 2" and 3" pads offer a seamless transition from rotary tools and are the perfect size for most faceplate projects. The tiny 1.5" models offer even greater range capabilities, as do the 5" and larger models.


Random Orbit Sanders: Advantages

  • Orbit Size - The tiny 3/32" random orbit on newer models leaves an incredible surface when used with finer finishing grits.
  • True Palm Size – Many pneumatic ROS are available in sizes that comfortably fit the palm of your hand and can be used for extended periods without fatigue.
  • Velcro Faced Pads – Most ROS are now available with Velcro faced pads for easy grit changes. Although Velcro faced abrasives are slightly more expensive than other abrasives, they are far easier to use. Most woodturners agree that the extra expense of Velcro abrasives is outweighed by their ease of use.

Sioux's Dual Action sander features
a 3" Velcro-faced sanding pad

Random Orbit Sanders: Disadvantages

  • Cost – ROS can be expensive, especially the pneumatically powered models and the high-end electrics.
  • Size - Some units are too big to fit in the palm of your hand, limiting their use to large and jumbo-sized projects that are better suited to the larger 6" and 8" pad sizes.
  • Compressor Capacity - If you go with a pneumatic ROS, you'll need a good size compressor. I use a heavy-duty industrial air compressor with a 5HP motor (240 Volt) and an 80-gallon reserve tank. If you have a compressor smaller than 5HP/60 gallons, it may lack sufficient power and air capacity to keep up with your tool.

Using a Dual Action sander to finish sand
the outside of a 16" Honey Mesquite
bowl with 800-grit abrasive

  • Use – ROS work best when the project is not turning on the lathe. Although you can use a ROS while the lathe is running, the RPM must be very, very slow. If the lathe runs fast, the ROS pad will stop or skip around on the surface, a condition known as "hiccupping."

ROS Protocol

As good as ROS are for finish sanding, I do not feel they offer significant advantages when using course abrasives. Therefore, I limit my use of ROS to grits above 400 grit (P400) and use traditional rotary pneumatic or electric tools for courser abrasive work. My typical protocol for a bowl is as follows:

  • Shear scrape the surface to 180 or 240 grit equivalent. This reduces the amount of sanding needed and further refines the desired profile.

Using the 3" AirVantage pneumatic palm
sander to finish sand a Mesquite platter
with 800-grit abrasive

  • Power sand with rotary pneumatic or electric drill with 180, 240 and 320-grits. After each grit, sanding dust is blown off and lathe direction is reversed. (Note: Chuck is locked onto the spindle with a grub screw to prevent the chuck from unscrewing when reverse sanding for safety. Some lathes do not offer this safety option.)
  • Use a ROS for 400, 600 and 800-grit abrasives. After each grit change, dust is blown off and lathe direction is reversed. Depending on the project, finer grits may be used above 1,000-grit.

Recommendations

If you already have a suitable compressor, take a look at a palm sized ROS. Try it on some of your projects and see what you think… If you're like me, you'll find that a ROS is another tool worthy of being in your woodturning toolbox. It gives you additional options for those projects that can benefit from the dual sanding action and on those that incorporate mixed media inlays.

Metabo's electric random orbit sander
features integrated dust control and a 3"
Velcro-faced sanding pad

If you do not already own a compressor, look for electric model ROS or stay with your current rotary action sanding options. The costs involved with getting setup for pneumatics can be prohibitive and may be better spent on other tools that will help you to grow as your needs and desires change.


Safety Note: Always follow all manufacturers safety instructions before working with your lathe, or any of the tools or products you may use. If you are unsure about any operation, obtain competent professional instruction before proceeding. Use and wear all necessary safety devices during turning and observe safe woodturning practices to prevent accident or injury.


Steven D. Russell is a professional studio woodturner, teacher and writer. He has written numerous articles for international woodturning magazines, which have been published in more than 78 countries around the world. Steve has demonstrated in numerous cities across the United States. His studio, Eurowood Werks, specializes in bowls, platters and hollow forms with unique visual and tactile treatments.

Steve is also the current and founding President of the Lone Star Woodturners Association, Inc., an AAW member chapter. The LSWA is a 501(c)3 non-profit educational organization dedicated to teaching and demonstrating the art and craft of woodturning.

Steve is also a featured writer for the Guild of Master Craftsman's "Woodturning" magazine, published in London England. Woodturning magazine is the world's leading magazine for woodturners. Look for his articles covering technical topics, or project based articles in an upcoming issue.