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  • Sanding issues

    Hi all, New to this forum and I have an issue sanding wood rounds. I am using a Dewalt 5" random orbital sander to sand the rounds which are roughly the same size as the sander and about 3/8 thick. After cutting on the miter saw and sanding with 80, 100,180, 220, 320, 400 grit paper I am finding the round become concave - high in the middle on both sides of the pieces. Using as coasters so this is not the best situation. I contacted Dewalt and they sent a new bottom which did not help. I am stuck trying to figure out why this is happening and how to stop it. Rounds are mostly cedar, maple and black walnut. Any suggestions would be great! If you need more info pls let me know.
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  • #2

    Re: Sanding issues

    I think I would expect that using your technique. I would probably sand it manually by holding the wood round and sanding it against a sheet of paper on a flat surface.
    smallerstick, John@Hamilton and 2 others like this.

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    • #3

      Re: Sanding issues

      And if I were to do it with an orbital sander, I'd probably inset the wood piece inside a piece of wood with the same thickness. What you want to prevent is uneven sanding at the edges, which happens if you go past the wood piece with your sander. Not sure how feasible that is if your pieces are not all the same thickness.
      wrcooke likes this.

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      • #4

        Re: Sanding issues

        Originally posted by wrcooke View Post
        Hi all, New to this forum and I have an issue sanding wood rounds. I am using a Dewalt 5" random orbital sander to sand the rounds which are roughly the same size as the sander and about 3/8 thick. After cutting on the miter saw and sanding with 80, 100,180, 220, 320, 400 grit paper I am finding the round become concave - high in the middle on both sides of the pieces. Using as coasters so this is not the best situation. I contacted Dewalt and they sent a new bottom which did not help. I am stuck trying to figure out why this is happening and how to stop it. Rounds are mostly cedar, maple and black walnut. Any suggestions would be great! If you need more info pls let me know.
        On an orbital sander the edges of your sandpaper are moving very quickly, but the centre is hardly moving. Sure it's the same RPM, but the distance the centre travels is very little. Reminds me of an experiment we did in elementary school when we went skating, everyone locked hands and skated in a circle...the people in the centre were hardly moving and the people at the ends were holding onto dear life. So it would make sense that the edges of your workpiece are wearing down quickly. Sancyk has a good solution that would allow you to use the whole pad of your sander for even sanding.
        corpaul, ThePracticalPeasant and 2 others like this.

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        • #5

          Re: Sanding issues

          Thanks folks, I agree the orbital sander would be fast on the outside and much slower in the middle. Perhaps its just that simple. Maybe I'll try a 1/4 sheet sander and see if I get the same results.

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          • #6

            Re: Sanding issues

            Originally posted by wrcooke View Post
            Thanks folks, I agree the orbital sander would be fast on the outside and much slower in the middle. Perhaps its just that simple. Maybe I'll try a 1/4 sheet sander and see if I get the same results.
            Nugsthecat is correct, I always wonder why everything has to be done using a power tool when it actually cost you more, in the good old days just before I came into the workforce it was all done by hand and there is still a place for it, a random orbital sander is better than an orbital sander but there are still limitations and problems with them.
            I too have just been using a RAS and have created myself a problem that I am now sanding out by hand, after more than 50 years playing with wood I am still learning, I think it's the challenge that keeps me going.
            wrcooke, KenL and John@Hamilton like this.

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            • #7

              Re: Sanding issues

              Try sanding up to 220 before cutting the round. Then you are sanding a big flat surface and just a touch up on the round
              wrcooke, and like this.
              Dara
              SPCHT

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              • #8

                Re: Sanding issues

                Originally posted by Dara View Post
                Try sanding up to 220 before cutting the round. Then you are sanding a big flat surface and just a touch up on the round
                X2 on this idea.
                Previously Wallace's Dad

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                • #9

                  Re: Sanding issues

                  glue your sandpaper to a stick or small flat board. go through the grits again, stopping once you get full contact on each grit.

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                  • #10

                    Re: Sanding issues

                    I am not sure what rounds are but could I assume that they are slices of branches or logs? If the middle is thicker than the edge, they would be convex rather than concave and that would indicate that the advice about the ROS that you have already is the bottom line; a ROS won't do what you need/want to do. How thick is the edge after sanding? Stickman has a great idea if there is not much to take off to get them flat again. I think that you will have a similar issue with a pad sander since it too basically rotates about a fixed point.

                    My 2 cents

                    Ken

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                    • #11

                      Re: Sanding issues

                      Ive been sanding up some old fir casings and they are flat grain. Yes the ROS will hog out the soft parts. what I often do is just use the ROS anyway, to get down into the wood and through its hard aged "shell" this is so I dont have to fight so hard. Then I use a card scraper. The card scraper wont hog out the softer grain like the sander so it evens it up. a card scraper may also work here but it is end grain so a bit slower going. I'd often rather run a card scraper, then I dont need to buy sandpaper and the dust is not so fine so it's cleaner, not scattering dust through the room. That's important sometimes if you are working in a finished space and dont want a room full of sanding dust.
                      Takes a bit of practice to keep it sharp and hold it right but anyway , It's often my option of choice. quieter too. Hand sanding or scraping , it's often an option to think of and try. It might be easier to start practicing on flat grain and edge grain, and if it is solid, clamped on the bench so you can lean into it then it's much easier, the piece isn't shifting and you have better ergonomics if you can lean down on top of the piece.
                      but it will work. You have to watch the edges and work inwards so it doesn't' chip out near the edge. If you are familiar with chiseling and using your chisel in a sort of paring or twisting motion you can use that sort of technique with the scraper in tight spots. it has to be sharp like an ice skate.


                      Even if you are hand sanding you can put a card scraper on the surface and place a flashlight behind it and see where the hollows are that way. you will see light where there is a low spot. I'm not sure of the finish you will be applying , sometimes I'd go to about 60 or so and then start using oil and wet or dry sandpaper ( the black stuff) soaked in a little dish. it cuts pretty fast, the oil actually cools the paper and works as a cutting fluid so it cuts faster like that. the paper wont clog up so it keeps cutting better, the paper lasts a long time. if you use something flat behind the paper it will sort of suck down like if you put two sheets of wet glass together. Id cut a little board to just a bit smaller than 1/3 sheet. x 11 inches, or a bit smaller than 1/2 sheet. keep the 11 inch length.

                      it fills voids with the dust and after a few sessions it will become smooth and shiny. the dust and some oil will penetrate the voids in the end grain. the dust and oil will collect and fill the voids leaving a nice shiny smooth surface. I'd give it time and do it for a while over a few days to let it penetrate and dry and do more.
                      Then if you like you can use a topcoat of poly or shellac or something, or continue with the oil.

                      I won't wet sand with the sander as this would just make a mess of the sander.

                      I'm sure there are other ways to choose, matter of preference. Belt sander will cut faster than ROS if you need faster but also takes some practice to control it. you could make matters worse too, but as long as you dont run out of wood you can try things.

                      any machine leaves it's marks. the ones from a ROS are circular. the handwork generally removes the machine marks. If you use a hand plane or a thickness planer or a different sander or a saw blade or a vibrating sander they all have their patterns that they leave behind. Often these patterns can be amplified as you apply your first finish, they may jump out.

                      If I start applying oil I am looking for such marks and basically erasing them as I go. I'd prefer that to doing a finish coat and being disappointed when they seemingly jump out from nowhere. most machine sanding marks can be improved by a little hand work where you are going with the grain and trying not to leave patterns.

                      I find if I am spending a lot of time at something I'll often use that time to think gee there must be a better way and I'll experiment then. Sometimes through the job you find your own preferences and techniques that work best for your situation.

                      In general you can usually go through the grits with each machine you use. In some cases maybe you stop and use other methods as you go finer or more finished.

                      I'd consider the ROS a valuable tool but maybe not a tool that I expect to always leave a perfectly finished and prepped surface. if you want a perfect surface it's just more time and work. where you draw those lines is personal. some say good enough and some want to go forever with less and less gain for the time spent. ( the law of diminishing returns)

                      Sometimes you may want it good enough, and done and sometimes you want it as perfect as possible. that's the craftsman's decision.

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