# Orbital Sander scuff marks....



## JoeMemphis (Jan 19, 2013)

Hello again, sorry for the multiple questions in a row...my go to advice guy on all things Woodworking (My Dad) passed away this year. 

I made a coffee table last year and used a orbital sander going from 80, 120, to 220, sand grit and it felt as smooth as a baby's butt. but when I stained it, a couple of swirl marks appeared. My question is what is causing that/how to prevent it. Because I couldn't tell after sanding that the swirl marks were there but they showed up after staining it. Any help would be appreciated. 

Thanks,
Joe


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## Steve Neul (Sep 2, 2011)

Your sander might run a little slow but I think probably you just didn't sand it long enough with the 120 and 220 paper. Some woods just show swirl marks more than others anyway. It helps if you wipe the wood down with a damp cloth between grit changes and raise the grain. This will make your sanding more effective.


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## Quickstep (Apr 10, 2012)

80 grit can leave some pretty deep scratches and you may need to spend some extra time with the next grit to get all the 80 grit scratches out. Using more in-between grits helps too. When I sand to 220, I usually start with 80, then go to 100, then 120, then 150, then 180, then 220. I usually do the 220 grit by hand sanding with the grain.


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## JoeMemphis (Jan 19, 2013)

Thanks for the tips, I'll have to go get a wider variety of grits, I was going with what Home Depot had to offer...I'll try it on the matching end tables...thanks


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## HowardAcheson (Nov 25, 2011)

Here is some info on sanding that may be helpful.

Sanding wood--hard or soft--beyond 220 does little more than burnish the wood making staining difficult. This is particularly true if you are using a pigment stain which sits on the surface and relies on "nooks and crannies" to impart color. Softer more porous woods can be sanded to to 220 but harder less absorbent woods may stain best if only sanded to 150. The best compromise is to aim for 180 grit. 

A number of years ago a large cabinet/custom furniture shop I was involved with did series of adhesion tests with various finishes and sealers. As part of this test we explored adhesion based on sanding grit. We found about the same adhesion up to 180 - 220. Beyond 220 adhesion dropped off due to burnishing of the underlying wood particularly when non-linear machine sanders were used. This was tested on birch and maple panels. We also found that the resulting smoothness of the first coat of finish was not materially affected by the smoothnes of the underlying wood for sandpaper grits between 150 - 220.. The smoothest surface substrate for final finishes was obtained by sanding lightly after the first coat of finish was applied and dry. Which makes the case for a thinned first coat of finish.

So our conclusion was that sanding beyond 180-220 was not necessary and could be actually detrimental. 

But, most important was that there was a big appearance affect if the surface was not HAND sanded in the direction of the grain using the highest grit used on the sanding machine. A flat pad sander produced a much flatter surface than a ROS. However, both required final hand sanding with the grain for optimum appearance. If not hand sanded, swirl scratches could show. Final hand sanding using a sanding pad in the direction of the grain is a must. 

To carry it one step further, sanding at 320-400 grit after the first coat and subsequent coats was the optimum. No improved appearance was noticed by between coat sanding beyond 400 for varnish. 400 was the sweet spot for thinner finishes. Between coat sanding was always done by hand whether for flattening or for adhesion. 

I think you will find similar thoughts in the popular finishing books by Jewitt and Flexner.

Finally, the first coat of ANY finish will soak little shards of wood and cause them to raise whether the surface was sanded, planed or scraped. When the first coat of finish dries these hardened shards are what causes the surface to feel rough. Sanding with 320 paper will remove these hardened shards and subsequent coats will go on smoother. So, smoothness counts after the first coat of finish, but not much before that.

The finish left by the sizing machine determines the starting grit. Jointers, planers, belt sanders etc, should leave a finish that allows starting with 100 grit. From there, go to 120 grit and sand until the marks from the prior grit are gone, then move to 150 and finish at 180 grit.

Plywood is factory sanded to 180 grit. Therefore, it's best to not sand plywood except with 180 grit and sand by hand. Get the first coat of finish on and then sand with 320. That way you are sanding the finish, not the wood. This avoids sanding through today's very thin surface veneer.


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## epicfail48 (Mar 27, 2014)

In my experience, when I see swirl marks its because I get impatient and run the sander too fast. Happens a lot, iM very impatient... At any rate, try going back over with the 220. Another fwiw, I usually stop at 180 for face or edge grain and do 220 for end grain. The 220 may help in some cases, but for most stuff that I do the 220 on everything just burns excess paper. Also as far as the paper grits go, I do the Steve Ramsey way of 80-120-180. Does it for my projects.


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## Brian T. (Dec 19, 2012)

"You didn't sand it long enough."
I'm in Steve Neul's camp on this.

Most of my wood carving is either western red or yellow cedar. Very soft.
It's always my hope NOT to have to sand with 80. The issue is to get rid of all the big scratches. One or two in what is supposed to be a glossy, smooth finished surface always looks like Hello. Always.
Ask yourself: Do you really have to start with 80?
The orbital is the kiss of death as the coarse sanding grits cross-cut the wood fiber.
Not a good plan.


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## del schisler (Nov 5, 2009)

JoeMemphis said:


> Hello again, sorry for the multiple questions in a row...my go to advice guy on all things Woodworking (My Dad) passed away this year.
> 
> I made a coffee table last year and used a orbital sander going from 80, 120, to 220, sand grit and it felt as smooth as a baby's butt. but when I stained it, a couple of swirl marks appeared. My question is what is causing that/how to prevent it. Because I couldn't tell after sanding that the swirl marks were there but they showed up after staining it. Any help would be appreciated.
> 
> ...


probly didn't sand enough, real hard wood ? like was mention wet it with thinner that you are going to use , like lacquer thinner ? that way you will be able to see the mark's , make sure and use good disk's also cheep one than the grit come's off and can cause them also,


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## Rick Mosher (Feb 26, 2009)

You don't say what type of stain you are using. A wiping stain will enhance swirl marks even more by pushing pigment into the swirls as well as any scratches or dents etc. 

If I am using a dye stain I make a very thin solution of the color I am going to use and pre-stain after the initial sanding, this will bring out any defects and is really easy to sand off. Similar to using a guide coat when sanding car paint.


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## Carvel Loafer (Dec 31, 2011)

Howie's write up is a great help. I learned some from that but have always hand sanded in the grain direction as he suggested. I have never trusted orbital or ROS sanders to give me the final touch.


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## Steve Neul (Sep 2, 2011)

While there is nothing wrong with hand sanding with the grain, I never hand sand any flat surface and I don't get any swirl marks. The orbital sander will remove the swirl marks if sanded long enough with the correct grit paper. I normally belt sand wood with a 60x belt to remove planer marks first. Then I sand with 80 grit on the orbital, then 150 and finally with 220. Depending on the wood I wet the wood and raise the grain between grit changes.


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## JoeMemphis (Jan 19, 2013)

Thanks for all the help everyone. I used soft cheap common board and just a brush on minwax stain. i'll have to sand longer (not my favorite part of woodworking) and dampen the wood between grit changes. Thanks again...


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## JoeMemphis (Jan 19, 2013)

Quick question just came to me...would using a sheet sander be better than an orbital sander?


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## Steve Neul (Sep 2, 2011)

JoeMemphis said:


> Quick question just came to me...would using a sheet sander be better than an orbital sander?


A lot would depend on the wood you are sanding. The felt pad on a sheet sander is softer than a random orbital sander. For example a wood like pine that has larger areas of hard and soft wood the sheet sander is prone to sand more of the soft wood out leaving ridges where the hard parts of the wood are, more or less giving the appearance of old worn wood. A wood like oak would probably sand fine. Personally when I bought my first random orbital sander I never went back to a sheet sander. It works well for any wood.


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## JCCLARK (Jan 30, 2007)

The biggest mistake people make with RO sanders is going back 
and forth to fast (like they do on TV shows)
Like the instructions say, you have to move slowly.
Most people never do.


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## knotscott (Nov 8, 2007)

I didn't read all the replies, so this may have been mentioned, but I've always considered some swirl marks par for the course with ROS. After going through all the grits, I follow the ROS with fine grit paper on a sanding block and finish the sanding by hand.


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## HowardAcheson (Nov 25, 2011)

In our shop, we used straight line air sanders for most sanding above 150 grit. To get the most professional look of a perfectly flat surface, you don't want to use a ROS. ROS's do not sand to a flat surface or maintain a flat surface. Straight line pad sanders do not ride up and down over non-flat surfaces


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## WonderlandWoodworks (Oct 23, 2013)

*Another thing it could be...*

Something else it could be in sawdust build up in between the sander and your work surface. If you are not using any kind of dust extraction sawdust can build up and score your work surface while you sand. The little bag attachment on the sander will get some of the stuff up but if you can hook up even a shop vac to your sander it will pull a lot more sawdust out and minimize the swirl marks.


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## JoeMemphis (Jan 19, 2013)

Started sanding another project and came up with another question: would running the orbital sander too fast cause scuff marks?


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## Steve Neul (Sep 2, 2011)

JoeMemphis said:


> Started sanding another project and came up with another question: would running the orbital sander too fast cause scuff marks?


Yes, moving the sander around too fast can cause swirl marks that you wouldn't otherwise have.


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## JoeMemphis (Jan 19, 2013)

I meant the speed setting...


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## Al B Thayer (Dec 10, 2011)

Joe 

Change the sheet before its worn smooth. Never set it down on the sheet. It can pick up something that could scratch. If you can set it down on a scrap piece of carpet it will help clean the sheet and keep it from loading up.

Worn sheets can "polish" the wood not sand it making it feel sanded.

Al


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## Al B Thayer (Dec 10, 2011)

HowardAcheson said:


> In our shop, we used straight line air sanders for most sanding above 150 grit. To get the most professional look of a perfectly flat surface, you don't want to use a ROS. ROS's do not sand to a flat surface or maintain a flat surface. Straight line pad sanders do not ride up and down over non-flat surfaces


I can agree that the ROS doesn't sand flat enough. My pad sander had a pad that was too soft so I made a pad that was a little harder. Not very forgiving but makes a really flat top.

Al


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