# Cleaning up a wavy pattern from sanding with ROS



## garlandkr (Apr 13, 2014)

I've read that using a ROS can remove the soft wood quicker than the grain which leaves a wavy pattern. Had I known that before starting I would have gone with a different approach.

I am working with a slab of Sweetgum that has some twist to it that will remain with the piece. I used 100 grit in the ROS at about 10k rpm and went over the twisted corner with multiple passes. Now there is a wavy look to that end in a few areas.

What are some methods to remove this? I don't have a card scraper but have considered buying one for this use case. Also, the top right area is angled due to a twist in the board so a plane is not going to be usable. Maybe a block of slightly curved wood with sand paper attached could do the job? If so, how should I apply the strokes, with the grain?










EDIT: I've gone back with the ROS and 60 grit and it looks promising. This is after about 2-3 minutes worth of sanding. There are a few spots which appear to have fewer lines running so I think I'm on the right track.


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## ChefHDAN (Aug 7, 2010)

I've never seen that before from an ROS, it reminds me a bit of lumber from the mill that cut with the BS in a bit of a wave pattern. I got better results from my ROS when I read somewhere about moving the ROS slowly enough for the orbit to cover it's own scratches, it's not slow motion but I used to be in the habit of moving the ROS quickly thinking the boring job would be finished faster, when it turns out better technique was actually better and a bit faster. My best idea would be to see if it is actually from the sawyer and try to sand it out. Sorry not much help, but it's a thought, and go ahead and order/get the scrapers, once you've got them you'll always have a spot where they come in handy.


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## pjones46 (Mar 1, 2011)

Appears to be planer marks from gong though it to fast, or bandsaw marks from milling. I use a belt sander first then the ROS as a finish up. Sometines I even use a hand scraper prior to using the ROS.


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## a1Jim (Aug 9, 2008)

I haven't used sweetgum before so I don't know if its a charismatic of that wood. Sometimes wavy surfaces are due to poor sanding technique ,such as putting excessive pressure on your ROS or tilting the sander as you sand. You need to let the sander do the work not apply too much pressure. A card scraper is a good idea or just a *flat* sanding block not curved or even a belt sander if you have experience with one otherwise they can be a project killer. Some ROSers are more aggressive than others that could contribute to the problem especially if a bad technique is used. Another approach is if your technique was not good ,start with 60 grit do a very even pattern and work your way up through the grits up to 150 or 180 . 60,80.100.120.150.180.


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## a1Jim (Aug 9, 2008)

The photo just appeared after I posted ,I think I'd start with a belt sander then go through the sanding steps in my other post. If you don't have a lot of experience with a belt sander just make sure you don't leave it in one spot too long keep long flowing movements. start with 60 grit on your belt sander.


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## ChefHDAN (Aug 7, 2010)

Looks like we were all typing at the same time… LOL


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## TheFridge (May 1, 2014)

What they said or

Get a #4 and a card scraper


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## garlandkr (Apr 13, 2014)

Thanks for the quick replies. I was hesitant in using a belt sander as I don't have experience in using one and didn't want to remove too much material. Plus, I don't have one. But I'm known to go and buy things like that on an as needed basis, so if I need it for this I'll get one.

I didn't see any marks left from the sawyer, here is a photo of that same side before I sanded it.


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## a1Jim (Aug 9, 2008)

Actually I can see some,I think the sanding made them more apparent.


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## garlandkr (Apr 13, 2014)

Well, if that's the case should I just go back to the ROS with maybe a lower grit? I have 80 on hand.


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## a1Jim (Aug 9, 2008)

If that's the lowest grit you have you could try a area an see how it looks.


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## a1Jim (Aug 9, 2008)

When you can it would be good to purchase a whole range of sand paper starting as low as 36 grit up to 220.

This might help in general

http://lumberjocks.com/a1Jim/blog/43345


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## a1Jim (Aug 9, 2008)

This might help too


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## Tennessee (Jul 8, 2011)

I would not use a belt sander. It will hog off the wood too fast.
I'd go with the 80 grit on the ROS and see how well it takes out the blade marks.

Those are definitely marks from the blade at the mill. Sometimes the saw blade can actually compress the softer woods a bit when cutting, so they are not as apparent until you take off the first rough surface.

Nice piece of wood, though!


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## garlandkr (Apr 13, 2014)

> I would not use a belt sander. It will hog off the wood too fast.
> I d go with the 80 grit on the ROS and see how well it takes out the blade marks.
> 
> Those are definitely marks from the blade at the mill. Sometimes the saw blade can actually compress the softer woods a bit when cutting, so they are not as apparent until you take off the first rough surface.
> ...


Thanks! I especially like the other end of it where some spalt was discovered after some sanding. I am trying to be cautious on that end as I want to keep the current look and not sand too much of it away. I'm planning to cover it all with epoxy when it's done being sanded as there is some rot and the checking is deep.


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## ElChe (Sep 28, 2014)

Cabinet scraper can be had fairly inexpensively and much less tiring to use than a card scraper. Like a Stanley no. 80?


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## garlandkr (Apr 13, 2014)

> Cabinet scraper can be had fairly inexpensively and much less tiring to use than a card scraper. Like a Stanley no. 80?
> 
> 
> 
> ...


Truth be told I don't want to drive the 3 hours round trip to the nearest shop which has wood scrapers available. I will likely purchase a scraper online for future projects.

I updated the first post with a new picture after some more sanding.


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## a1Jim (Aug 9, 2008)

Sorry to disagree, but a belt sander does not have to hog off too much unless you don't use it properly or have too aggressive of sandpaper on it. the link above shows how to use a belt sander properly and is using it on some thinly veneered plywood without any harm at all. 




garlandkr
it just depends what your thoughts are,if this is a one-time project maybe you don't want to invest in more tooling and learning how to use tools you are afraid will damage your project,but if you're going to be doing more projects in the future you time and money may be well spent with better equipment and improved skills. We have all been there at the beginning ,from my point of view it has been worth the effort for me.


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## teejk02 (Apr 27, 2015)

You don't mention what type of ROS you are using. I have one that looks like an auto buffer/angle grinder (PC something). I don't use it much because I find it hard to keep flat and it was easy to create "craters". Never had a problem with the PC 343 type though. The key to them is to forget about the top part, grip it lightly around the throat like a beer can and let the machine do the work (keep it moving though). You probably already know about that though since even slight downward pressure on the tool will not let it spin. I only keep 80, 150 and 220 on hand (plus some really fine grits for buffing out poly). You said the wood was soft so 80 should be fine. As for belt sanders, does anybody use them much any more after the ROS became popular? Mine has been collecting dust for a long time.


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## garlandkr (Apr 13, 2014)

> You don t mention what type of ROS you are using. I have one that looks like an auto buffer/angle grinder (PC something). I don t use it much because I find it hard to keep flat and it was easy to create "craters". Never had a problem with the PC 343 type though. The key to them is to forget about the top part, grip it lightly around the throat like a beer can and let the machine do the work (keep it moving though). You probably already know about that though since even slight downward pressure on the tool will not let it spin. I only keep 80, 150 and 220 on hand (plus some really fine grits for buffing out poly). You said the wood was soft so 80 should be fine. As for belt sanders, does anybody use them much any more after the ROS became popular? Mine has been collecting dust for a long time.
> 
> - teejk02


I agree with that, the ROS likes to run away. I have learned to keep a hold on it by the round base like a beer! I just guide it more or less, a little bit of downward pressure like I'm writing with a pen just to keep it from trying to jump around.

It's a Ridgid 5" that I have hooked up to my Ridgid vac.


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## teejk02 (Apr 27, 2015)

> I agree with that, the ROS likes to run away. I have learned to keep a hold on it by the round base like a beer! I just guide it more or less, a little bit of downward pressure like I m writing with a pen just to keep it from trying to jump around.
> 
> It s a Ridgid 5" that I have hooked up to my Ridgid vac.
> 
> - garlandkr


Ridgid/PC/Dewalt probably all operate the same…I figure my only job is to keep it from walking out the shop door. I change the sandpaper frequently especially with the 80 grit…ready to buy a new one that will better accept a shop vac and perhaps they'll last longer but even without I think a box of 50 hook & loop runs about $15 from Online Industrial Supply (I shake my head at what the retail stores charge for 5).


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## JoeinGa (Nov 26, 2012)

The reason you saw the "lines" after the initial sanding is because the ROS was riding ON TOP of the ridges caused by the milling. And you can see that as you sand more, those ridges are going down, hence the wood is looking smoother, because you are sanding the ridges out.

Keep on keeping on with the ROS, soon that slab will be smooth as a baby's butt !


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## rwe2156 (May 7, 2014)

I would put the sander away and try a hand plane, #5 ro 6.
If you can work it you'll get a better finish anyway.
Extremely sharp blade/close mouth/very light strokes.
I would start by going cross grain until the planer marks are gone then try sanding or scraping.

Sorry but have to disagree re: belt sander. IMO that is the quickest way to ruin the project if you are not extremely adept and careful with it.


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## a1Jim (Aug 9, 2008)

Planes can do a great job if you Have your plane set properly and know how to use one.


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## gfadvm (Jan 13, 2011)

Jim, Thanks for the belt sander link. I may have to revisit this tool. I have always felt that I could destroy a project quicker with the belt sander than any other tool in the shop! After watching the vid, I see where I can improve my technique.


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## a1Jim (Aug 9, 2008)

gfadm
glad you liked it.for some reason I've never had any trouble with belt sanders ,but I know it's a problem for some folks,glad it could be of help to someone with all of your experience,so people with less experience it might help also.


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## ElChe (Sep 28, 2014)

> Cabinet scraper can be had fairly inexpensively and much less tiring to use than a card scraper. Like a Stanley no. 80?
> 
> 
> 
> ...


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