Need advise on ROS operation

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Forum topic by SteveMI posted 03-03-2010 11:23 PM 1453 views 0 times favorited 12 replies Add to Favorites Watch
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1092 posts in 3260 days

03-03-2010 11:23 PM

Topic tags/keywords: sander sanding question

I finally broke down and bought a Bosch ROS20VS primarily based on my past experience with Bosch tools that I have. My prior sander was a non-orbital Bosch pad sander better suited to drywall than boards.

In trying the ROS out on some scrap boards, I have a question on wether it is working correctly or not. Per the instructions, I start with the pad on the surface and turn it on. I am not applying pressure, but guiding it over the board. I am using the vacumm adapter and small shop vac.

The ROS seems to stutter and jump at times which results in swirls or circular scratches. I can’t figure out any pattern to the stutters and jumps. This has occurred with two different grit papers. Overall the surface is quite smooth and much better than my prior sander.

Are the stutters, jerks and jumps common to a ROS? Did I get a bad one? Anything to adjust?


12 replies so far

View Sawkerf's profile


1730 posts in 3034 days

#1 posted 03-03-2010 11:28 PM

I get that sometimes with my DeWalt ROS. It seems to be be associated with “stuff” building up on the disc.

-- Adversity doesn't build reveals it.

View PurpLev's profile


8534 posts in 3614 days

#2 posted 03-03-2010 11:35 PM

another point to consider is what do you consider “not applying pressure” are you just pushing it from the side? or just applying very little pressure from the top?

I hold the ROS from the top, and do apply pressure (if you hold it from the top, it’s pretty impossible not to apply any downward pressure scientifically) but not enough to counteract the ROS performance. just use it like any other sander, but just don’t put enough pressure so that it interferes with the ROS random movement. the jumps might be caused by lack of grip on the ROS. especially since you mention that it’s random, and does not jump ALL the time – which would point to a bad motor/chassis.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View CharlieM1958's profile


16274 posts in 4184 days

#3 posted 03-03-2010 11:41 PM

Is the jumping happening during sanding, or just when you start it? Regardless of the instructions, I prefer starting the sander before I place it on the workpiece.

-- Charlie M. "Woodworking - patience = firewood"

View SteveMI's profile


1092 posts in 3260 days

#4 posted 03-03-2010 11:53 PM

Sandkerf – these were “new” discs and ony a few minutes of use

PurpLev/Charlie – the “no pressure” and “starting with the pad on board” were after my first playing with it and experiencing the stutters and jerks. Those were part of the manufacturer tool tips.

Charlie – it happens during sanding and not right away. Disc is very clean after sanding due to the vacuum.


View ,'s profile


2387 posts in 3513 days

#5 posted 03-04-2010 12:13 AM

Maybe it is an issue with your Bosch sander. We use the Ridgid model 5” ROS and we also had a 5” Dewalt model. Both of those sanders work smooth and operate nicely. I used to own a Bosch 5” ROS, I cannot remember the model number, but the feel of the sander while in use was not nearly as nice or well balanced as the Ridgid is. So I sold the Bosch 5” ROS on CL, since it worked fine, I could just tell it was far inferior to the Ridgid in terms of actual use.

With that said, we just burned out our 4th Ridgid ROS in the last 9 months this past week. So we just keep taking them to HD and exchanging them out and now I am on my 5th Ridgid ROS. The Ridgid 5” ROS is really well made and works great, but is not designed for prolonged extensive commercial usage. Just my experience. We also burned out the Dewalt sander but I had purchased it from a pawn shop so most of it’s useful life may have been behind it.

I also apply minimal to moderate pressure when using a ROS, it will do most of the work on it’s own though. If you are not going to do 30 doors every 6 to 8 weeks, go and get the Ridgid, probably overall a better sander.

-- .

View lew's profile


12018 posts in 3721 days

#6 posted 03-04-2010 12:25 AM

Running this type of sander is sort of like running a floor buffer (I became an expert in the Navy). Leaning it a little one way or the other will guide it and help prevent some of the “stuttering”.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View SteveMI's profile


1092 posts in 3260 days

#7 posted 03-04-2010 01:51 AM

I found a method! Seems that speed setting #6 or #1 – #4 can cause the problem. Speed setting #5 for the wood I am sanding (Poplar) works fine.

Sands just fine now. Pressure downward (within reason) doesn’t seem to have any affect.


View Alex Lane's profile

Alex Lane

500 posts in 3856 days

#8 posted 03-04-2010 06:36 AM

I had a slightly similar problem the other day while using my Porter Cable single-speed ROS while leveling out cured grain-filler on a desk top. I found that if I leaned the sander slightly to my left or right with very little downward pressure, I’d get the ‘skippys’, but if I applied a little firmer downward pressure, the chatter went away. I never have the problem when I avoid leaning the sander one way or the other. I was using 220 and 320 grit blue alumina zirconia hook-’n-loop sandpaper, btw.

I suspect that each brand and model of ROS has its own level susceptibility to this skipping/chatter. My first ROS was a Grizzly sander that I think cost me $20 brand new. I had never been to a sander RODEO until that machine!! I got bucked around like a crazy cowboy on a crazy 18000 pound Brahma Bull.(no offense to any real rodeo cowboys out there ;-D). Then I got my P-C ROS, and what a dreamboat… It purrs like a kitten in comparison, yet I doubt it’s the nicest sander out there. Probably a Bosch 1250DEVS or a Festool Rotex would top most sanders for smoothness and power. But then, again its usually the way a user handles the tool that determines its ease of use and effectiveness.
Glad you’ve got it figured out!!

-- Lane Custom Guitars and Basses

View Phillywood's profile


16 posts in 2991 days

#9 posted 03-04-2010 06:38 AM

Well, I can appeciate all that you guys posted. On the other hands, I have had porter cable ROS for a long time and I have used it in an unconventional ways on different surfaces. I did happened to change out the bottom plate only once, just becaue i over forced it to do the corners of plywood that chewed up the edges on the bottom plate. A point to note here, is that it says random orbital sander- that means it will rotate randomly. I seem to let the sander do its job and I just giude it. I haven’t expereinced the problems that you all encountered. I also look at the tool reviews before I go out and purchase a new tools. I believe since those guys who test out these features they do a good job for us the woodworkers out here. Now, Bosh 1/4 sheet sander was rated the best buy for a long time, but don’t know if they ROS is up to the task.

View Dyidawg's profile


51 posts in 2979 days

#10 posted 03-04-2010 07:35 AM

I have a HF 5” that I have had for a few months and paid less than $20

it has worked very well and I have not experienced the problems described above

-- Wow, that was easy. Just follow the directions and use some common sense.

View a1Jim's profile


117063 posts in 3543 days

#11 posted 03-04-2010 07:54 AM

I don’t think starting you sander while in contact with wood is letting it build speed like it should.

-- wood crafting & woodworking classes

View Phillywood's profile


16 posts in 2991 days

#12 posted 03-05-2010 06:00 AM

a1Jim/ I totally agree with you. I was under the impression that you have to let the saw come to its full speed before you put it down on the wood. the other point is that if you start it on the wood and lets say you are using an 80 grits sand paper, If youdont control it then it may take a gig chunk of your piece of wood that may end up costing you lots of heart ache to try to leel it to the other pats of your wood. Like I mentioned you just let the saw do its job and you just guid it. By pushing too hard on the surface you actually slow down the sander.

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