Random Orbit Sander for Large Vessels

[Randy Anderson]

A while back I purchased a ROS for doing the finishing work on my large hollow forms. It's been a huge improvement in my ability and results when sanding large hollow forms that are 15 - 30+ inches tall. It can be tough to get a clean smooth surface, keep the flow of the curve and have no swales or ridges over that much distance. At least for me. With a high gloss finish the surface needs to be free from undulations or they'll show. With the ROS and the 5" pad I can glide it up and down the vessel and easily spot where there's a ridge or a swale in the surface and work over them until gone and blended in. With practice and a good pad I can go up around sharper curves toward the opening or base and still watch for imperfections in the surface. They also leave a very nice sanded finish. In all the years of doing woodworking I've never owned one. Wish I had sooner.

Every time I post in this section I wonder if I'm repeating something already covered or something everyone else knows but me. I searched but didn't find a discussion on the topic. Sorry if a repeat.

 

[Dave Landers]

Here's another trick for finding those subtile flat spots, dips, and ridges: lay a hot glue stick along the surface - any gaps will show a discontinuity in the curve.
(OK, so maybe not everyone buys hot glue in 5 lb boxes of 10" long sticks. But I always have plenty sitting around)

 

[Dean Center]

Thanks for sharing, Randy. Even if it had been mentioned before, your (headslap) how did I not do this long ago? comments make the post poignant and fresh.

Do you use the RO sander on or off the lathe? If on, spinning or stationary?

 

[Randy Anderson]

Thanks Dean. I sand on the lathe and don't spin it. I let the ROS simply rest on the surface, no real pressure other than it's weight, and work the 12 to about 3 o'clock window. I have a fairly thick foam pad on the sander. I'll rotate by hand from the chuck or back of the headstock while keeping the sander moving around and watching the surface for undulations to appear. They're pretty easy to spot as a dusty valley or a ridge and then can work over them with wide passes to blend in. Like everyone here I've spent countless hours with a rotary sander and a 2" or 3" mandrel along with some sheet paper here and there. It's hard for me to do that over such a large area without leaving undulations or even creating some with low grits. I've really been pleased with the ROS surface, lack of visible scratches even at low grits and the ability to get a surface that's very very flat with smooth curves. I still use my rotary sander for the smaller radius areas around the neck or base where the curve can be steep or I want to be careful on specific spots.

 

[Darryn Achall]

So I've had a RO Sander for years and used it on flatwork and flooring. Can't believe I never thought to try it on my larger hollow forms. Will be trying that one this week!

 

[Lou Currier]

I use an air powered random orbital sander that uses 2 and 3" pads. It has greatly enhanced my sanding and finishing.

 

[Randy Anderson]

Lou, I tried but my small shop compressor wouldn't keep one running so opted for a Festool electric model. Needed a very small orbit for fine finishes and theirs is about the smallest out there. I've been so pleased with the difference in surface finish and hearing you use one with smaller pads I'm going to get one for smaller pads as well. I just finished a large hollow form, finished at 240 with the ROS and surface is better than I usually get with 320/400 with my rotary sander. I'm sold.

 

[Kevin Jenness]

I use a Milwaukee M12 rotary sander-polisher with a 2" or 3" mandrel for rough sanding vessels sander. For finish sanding I use a Festool 5" random orbit sander on the exteriors and a Grex pneumatic r.o.s. for interior surfaces. The rotary unit removes material faster and the random orbit ones give a better finish. The Grex is an underpowered air hog but it is light and highly maneuverable and gets the job done. I jury-rigged a limiter on the trigger to keep the speed down from the maximum 15,000 rpms.Grex ros

 

[Bill Boehme]

Here's another trick for finding those subtile flat spots, dips, and ridges: lay a hot glue stick along the surface - any gaps will show a discontinuity in the curve.
(OK, so maybe not everyone buys hot glue in 5 lb boxes of 10" long sticks. But I always have plenty sitting around)

I use a steel straightedge and rock it along the surface. Of course, that doesn't work for outward curves. I'll have to see if I can find a hot melt glue stick in one of my junk boxes.

 

[Brian Gustin]

I use a steel straightedge and rock it along the surface. Of course, that doesn't work for outward curves. I'll have to see if I can find a hot melt glue stick in one of my junk boxes.

or a length of 1/4 inch PEX water pipe tubing?

 

[Emiliano Achaval]

I started a thread about this a while ago. I said I needed to confess that I use the 5 in pads with Festool orbital sanders to do a lot of my sanding. Steve Worcester, owner of turningwood.com, says that only David Ellsworth and I use the 5 in. Most turners tend to buy the 3 in. When I design a piece, bowl, urn, box, etc. I think about sanding. That is one of the reasons why my bowls don't have a foot. The other one is that I'm inspired by the round bottom Hawaiian calabashes.

 

[Bill Boehme]

I have a six-inch ROS, but I've never considered using it on anything with a curved surface. I use my fingers more than my eyes to ensure that the surface is a fair curve.

 

[BobCoates]

I tried it today on a 12" high vase, was impressed how easy and quick it seemed to get a good finish. Only use 180 grit, but will try others before finishing. The lathe was turning at slow speed.

 

[Don Wattenhofer]

Here's another trick for finding those subtile flat spots, dips, and ridges: lay a hot glue stick along the surface - any gaps will show a discontinuity in the curve.
(OK, so maybe not everyone buys hot glue in 5 lb boxes of 10" long sticks. But I always have plenty sitting around)

Most of those low and high spots can easily be detected simply by moving your hand over the surface and that works equally on concave and convex surfaces.

 

[Bill Boehme]

Most of those low and high spots can easily be detected simply by moving your hand over the surface and that works equally on concave and convex surfaces.

While you might have to spend time searching for a hot-melt glue stick or a straightedge or whatever, your fingers are usually close at hand.

 

[hockenbery]

Straight edges - pencils, glue sticks, rulers are great for spotting flats in a curved surface
Fingers are great for finding bumps while hollowing a bowl.

 

[Michael Nathal]

opted for a Festool electric model. Needed a very small orbit for fine finishes and theirs is about the smallest out there.

I'm curious about the effect of the orbit on the sanded finish. I haven't heard this before. Can you point me to more info? Also, when you adjust the "level" on an ROS (usually a scale from 1 to 7 or something similar), are you adjusting the orbit size, or the speed/frequency, or both, or something else?

 

[Randy Anderson]

Michael, I'm new to using a ROS but from what I've seen online and my own use is the rotation and orbit produces a great finish. The level on the sander adjusts the speed of the motor and the aggressiveness of the cutting. My understanding is the orbit size is fixed. I keep mine on a little below the medium point for sanding and even lower for working with finishing. No science, I just do. I've used it a bit on some flatwork and the sanded finish is great. There are tons of youtube videos and online info pages on ROS use. A channel called Stumpy Numbs is one I use a lot and he has some info on using one. The things I try to watch for when using are very limited if any downward pressure. The weight of the sander is likely enough. If you notice the head isn't spinning, and it doesn't spin very fast, then you're pressing too hard. Keep it moving around on the workpiece. That's true for any sander I think.

 

[Gerald Lawrence]

I'm curious about the effect of the orbit on the sanded finish. I haven't heard this before. Can you point me to more info? Also, when you adjust the "level" on an ROS (usually a scale from 1 to 7 or something similar), are you adjusting the orbit size, or the speed/frequency, or both, or something else?

Not sure this answers your question. I have a RO sander from Woodturners Wonders, also a PC 5 inch and changing speeds does that only. The orbital mechanism is fixed for a circular motion and is not either contractable nor expandable. It does get aggressive at higher speeds

OOPs the other part of question is the effect of orbital. The orbit creats what might be called cross scratches instead of one circular pattern and this helps to disguise the scratch pattern

 

[Barry Richardson]

I use them all the time, they are especially good at getting rid of scratch marks from spin sanding

 

[Michael Nathal]

Ok my memory has recovered (a bit) to recall that the "level" dial on ROS is for speed only. But I still want to know how important is the orbit stroke in determining the quality of the finish. I watch Stumpy Nubs a lot but don't recall him talking about this specific issue.

 

[Kevin Jenness]

The smaller the orbit size the finer the scratches. Larger orbit is more agressive. Speed is adjustable but orbit size is fixed for a given sander. I use a Festool EC-EQ 125-3 with a 3mm orbit; they also make that model with a 5mm orbit. As Randy said, the disc needs to spin freely on the work to get the random effect, otherwise you have a simple orbital sander.

 

[Kent Reisdorph]

I'm curious about the effect of the orbit on the sanded finish. I haven't heard this before. Can you point me to more info? Also, when you adjust the "level" on an ROS (usually a scale from 1 to 7 or something similar), are you adjusting the orbit size, or the speed/frequency, or both, or something else?

I have an air sander. The level isn't adjustable. I used the RO air sander exclusively for the first year. Then I bought an electric angle sander/drill. I found the electric was much better at taking out tool marks at the lower grits, but it left bad scratches. Obviously these would be removed if I progressed through the grits with the electric, but the RO produces a much smoother finish more easily (for me). What I do now is work out the tool marks with the electric and then switch to the RO air sander for the rest.

Edit: After reading Kevin's reply, I checked the orbit on my RO. It's 3mm. My sander is only $33 on Amazon.

 

[Michael Nathal]

The smaller the orbit size the finer the scratches. Larger orbit is more agressive. Speed is adjustable but orbit size is fixed for a given sander. I use a Festool EC-EQ 125-3 with a 3mm orbit; they also make that model with a 5mm orbit. As Randy said, the disc needs to spin freely on the work to get the random effect, otherwise you have a simple orbital sander.

My intuition agrees that a larger orbit could very well be more aggressive. I still wonder about the fineness of the scratches. For example, consider two Festools, one with the 3mm stroke and the other with 5 mm stroke, both using 400 grit paper. Seems to me the grit of the paper would determine the fineness of the scratches. Especially if you are using the mesh type sandpapers like 3M Cubitron II that everyone seems to like. These would not trap sawdust on the wood surface, which might be an issue with regular paper and might well be worse with larger strokes.

Also, Randy can you give me your Festool model and what the stroke is? Most of the ROS I have looked at (Festool, Bosch, Metabo) are at 3 mm, with some at 5 mm

 

[Peter Van Rijssen]

I've been using the 3+" Metabo SXE400 ROS and getting good results. I've it both with the lathe spinning and off. The nice thing is I can hook up a vacuum as it has dust collection.

 

[Randy Anderson]

Michael, mine is a Festool 125REQ-Plus. It's an electric model with a 2mm orbit which is smaller than most out there. They make a lower profile model that has a bit larger orbit I think but still small (3mm I think). I debated on this model vs the lower profile model but the price difference didn't justify it and I've been fine with the one I have so far. Light enough to use easily for turnings or flat work. A lot of people opt for air powered models but my compressor was not enough to drive one and that cost upgrade would have been far too much to justify just for a sander.

 

[Doug Freeman]

My intuition agrees that a larger orbit could very well be more aggressive. I still wonder about the fineness of the scratches. For example, consider two Festools, one with the 3mm stroke and the other with 5 mm stroke, both using 400 grit paper. Seems to me the grit of the paper would determine the fineness of the scratches.

This is correct - the grit used determines scratch size. A larger orbits covers more area and is more aggressive. I think my ros I use for turning is 6mm. No issues with scratches going up to 800gr. Pressure applied to the tool is important - too much will produce “squigglies”, where dust builds up in the paper leaving orbit tracks.

 

[Kevin Jenness]

The grit size determines scratch depth. The orbit diameter has more to do with the screening effect of the random pattern, the larger the orbit the more visible the track is. That said, small differences in orbit sizes are not terribly significant. The pigtails Doug mentions are more of an issue especially when using stain.

Grit size is important but not the only factor in how smooth the surface looks and acts. Sanding with the grain gives the smoothest effect but we can't easily do that on faceplate oriented vessels. The easiest way to sand is hand sanding on a spinning surface but that results in cross-grain scratches, very hard to get rid of so we have to go to a higher grit level to make those scratches imperceptible. Rotary sanding is similar. Orbital sanders do a pretty good job of finish sanding, but random orbitals break up those regular scratch patterns and deliver a smoother appearing surface relative to a given grit size.

 

[Bill Boehme]

In addition to the fact that applying too much pressure ruins the screening pattern, it can also melt the Velcro hooks on the ROS. On flat woodworking the force shouldn't be any more than the weight of the tool itself. I would think that this also applies to sanding woodturnings.

 

[Randy Anderson]

Did second turning and initial sanding with 80 grit with the ROS on this black cherry piece yesterday. It's 33 1/2" long and the sander made all the difference in being able to address tool marks and subtle variations in the surface without changing the profile or creating new issues. Don't know how I would have addressed a piece this size with my 3" rotary sander and I don't like to hold paper and spin sand. When all the obvious areas are done I close my eyes and glide my hand across the surface. Where I feel very slight irregularities in the surface I can place the sander and let it glide around. You can actually feel the way the sander moves and when the surface gets flat the "glide" feel is noticeable. If there are slight ripples you can actually feel how it grabs and releases as it spins over them until it's flat. The finish and surface at 80 grit is far better than I get with a regular spin sander 80 grit.

If you look just below the inclusion area you can see some faint lines where the mineral spirits wipe shows some marks. Took care of those this morning.

 

[Brian Kopp]

I picked up a big old heavy 6” pneumatic random orbital sander today for $20, that looks like it was never used. It appears it was designed for auto body work and has a huge orbit variability. The Marketplace ad was for a 1.8hp 17 gallon Central Pneumatic air compressor, which I also picked up, and the ros was an incidental finding.

I usually use a Harbor Freight 55 degree drill with 3” disks for power sanding.

I was able to remove the 6” Velcro disk on the ros and replace it with a 3” Velcro disk, and of course I have lots of 3” hook and loop sandpaper in all the common grits already.

Is it “safe” to use an older 6” pos retrofitted with 3” disks on our bowls?

Does anyone have an opinion whether it will function properly on a 1.8hp, 17 gallon oil less compressor?

 

[Randy Anderson]

Brian, no way to know until you try I suppose. It'll let you know if it needs more air. I do know that ROS are real air hogs and it takes a lot to keep them going.

 

[Brian Kopp]

Brian, no way to know until you try I suppose. It'll let you know if it needs more air. I do know that ROS are real air hogs and it takes a lot to keep them going.

I just hooked it up and tried the 6” and the 3” disks. It works well but yeah, it’s a real air hog! This compressor is struggling to keep up with it.

 

[Randy Anderson]

Used it to finish the surface of a 12" platter this week. Great for making sure those subtle ripples are gone. The ones that you can't seem to feel or see until the first coat of finish is on or you set them on the table and the sunlight hits them just right.