Wet sanding with electric ROS

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Forum topic by Plain posted 07-11-2016 12:00 AM 1160 views 0 times favorited 7 replies Add to Favorites Watch
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157 posts in 847 days

07-11-2016 12:00 AM

Is it safe to use an electric random orbit sander with no hole discs for sanding topcoat with soap water ?

7 replies so far

View JBrow's profile


1366 posts in 1069 days

#1 posted 07-11-2016 12:24 PM


I personally avoid using electric tools around water whenever I can. I prefer to keep electricity and water away from each other. Even if sanding could be done safely, I would fear the toll it could take on the sander. A pneumatic sander would eliminate the safety concern, but the concern of the effect of water on the tool would remain.

If the wet sanding was with a volatile organic like lacquer thinner, paint thinner, mineral spirits or an organic solvent based finish, then definitely NO. The sparks from the motor brushes could ignite the solvent vapors.

View JoeinGa's profile


7739 posts in 2156 days

#2 posted 07-11-2016 12:56 PM

mix water and electricity???

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View jdh122's profile


1039 posts in 2967 days

#3 posted 07-11-2016 01:12 PM

As long as you’re plugged into a GFCI outlet I can’t see how there could be a safety issue. But it’s likely to kill or badly shorten the life of the sander. I’ve made several concrete countertops that had to be wet polished. Following the advice given by Fu-Tung Cheng (a leading expert on these) I used a random orbital sander on my first one (+GFCI), but it wrecked it quite quickly. I’ve since acquired a cheap variable speed sander-polisher that works way better and that keeps the motor a lot further away from the water. Polishing concrete is likely to be harder on it than wet sanding a finish, but still…

-- Jeremy, in the Acadian forests

View bigblockyeti's profile


5230 posts in 1870 days

#4 posted 07-11-2016 02:29 PM

I’d personally use a pneumatic sander for such a task, the danger isn’t worth the risk.

-- "Lack of effort will result in failure with amazing predictability" - Me

View bigJohninvegas's profile


491 posts in 1611 days

#5 posted 07-13-2016 01:12 AM

Are we talking about spray bottle wet, or bucket of water and a sponge wet?
I have wet sanded with a corded drill on my lathe just fine. But I’m only using a spray bottle to keep my work wet.
If spray bottle wet, I think your ok. If sanding something like a table top, I think I would make a real effort to keep the cord off the wet surface. And jdh122 is right. GFI protected.

-- John

View CharleyL's profile


223 posts in 3513 days

#6 posted 07-13-2016 09:18 PM

Don’t fully trust a GFCI. It’s good insurance for an accidental contact with electricity, but don’t plan on it to save your life when you are playing with electricity and water on purpose. They are good, but not reliable enough to depend on like this. Body shops use pneumatic sanders when wet sanding, or they do it by hand. Keep the electricity and water away from each other. I would never wet sand with a solvent unless I was at least 300’ from electricity and things that could generate a spark. Steel hand tools can spark under the right conditions. In other words, don’t do it.


View pintodeluxe's profile


5758 posts in 2962 days

#7 posted 07-13-2016 09:31 PM

My real worry is that you’ll blow through the topcoat. That’s as painful as being shocked.

I use 1000-1500 grit soft sanding sponges and tap water in a spray bottle.
Working with the grain a desk takes 20 min, and a large cabinet maybe 30 minutes.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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