Does Changing Speeds on a R.O. Sander Make a Difference?

Does Changing Speeds on a R.O. Sander Make a Difference?

How should the speed and grit of paper be used on variable speed random orbit sanders? My background is in aerospace manufacturing. In metal machining, fewer cutter teeth equals lower rpm and more teeth will allow higher rpm. By this convention, lower grits would run at the lower speeds and the speeds would increase for the higher grits. Bigger grit equates to less teeth and smaller grit to more teeth. I usually apply this convention, but I have tried reversing it or just using the same speed for all. Really can’t see much difference in the final surface. Maybe your resources can shine some light on this, or did manufacturers just give us variable speeds because we thought we should have it? I know some still offer single speed along with the variable speed sanders. – Dennis S. Cropper

Chris Marshall: Dennis, as you point out, I’ve seen no real difference either in cutting efficiency by varying the speed of my sander relative to the coarseness of grit I’m using. I think the bigger issue, regardless of speed setting, is to not push down on the machine while sanding in an attempt to speed the process along. The sander should be allowed to spin freely and under its own weight plus light hand pressure. It ensures that the orbital action will work properly so the grit abrades the surface as efficiently as it can. Beyond that, I’m not certain that variable speed control makes much difference at all to the final surface smoothness. I set my random-orbit sander to maximum speed for any grit I’m using and leave it there all the time.

Interestingly, a manual that came with a Bosch variable-speed R.O. sander I own makes some recommendations on speed settings to use for woods, metals or paintwork. While the dial can be set from 1 (low) to 6 (high) speed, the recommendation is from 4 to 6 on all surfaces and with all sanding grits besides light sanding on paintwork (2 to 3 is recommended, in grits ranging from 180 to 400). Setting 1 isn’t recommended for any sanding situation. So, at least according to this manufacturer, medium to full speed is suitable for pretty much every sanding task.

Rob Johnstone: Ah, sanding, the root canal of woodworking. I confess that I do not adjust the speed of my R.O. sanders at all. I set it at full speed and that is it. When using abrasives to smooth a wooden surface the goal is to get a uniformly smooth result. So after you’ve started with an appropriately coarse grit to quickly and effectively remove the surface blemishes, scratches and glue blobs, the next goal is to remove the scratch marks that you just installed on the wood’s surface with the 60-grit (40-grit?) product you just used. (When you remove all the 60-grit scratches, you move up and remove all the 80-grit scratches, and so on.) There are two speeds to be thinking about when using a R.O. sander: the setting on the machine (which I’ve already said I ignore) and the pace at which you move the sander across the wood. Most of us move the sander far too quickly — like we are polishing our shoes or something. A correct pace is about 1-inch per second. When you first try it, that speed will seem SO SLOW! But it allows the machine to properly do its work, and you will soon learn that by slowing down in that regard, you actually spend less time sanding overall. My opinion is that once you get through sanding with 180-grit using a sander, it is time to move to hand sanding with 220-grit and higher.

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  • TexasTimberWolf

    In my humble experience the speed setting on an RO sander (primarily a 6″ one) serves two purposes: 1. to eliminate resonance created by the vibration of the sander and transferred to the work piece, leading to the sander hopping and skipping uncontrollably and 2. to reduce heat build-up on sticky surfaces like painted or lacquered items when using rougher sanding discs that clog due to the melted coating. The lower the speed, the less friction and, thus, less melting. – Just food for thought.

  • bob peter

    i don’t like full speed and do all sanding at about 1/2 speed. bob

    • Alan Gosling

      What about slow sanding, what do you use it for and when looking at which one of these sanders would you recommend buying?

  • Craig Pierpont

    For finish sanding, where the difference between “Very nice and “Oops” is a matter of a second or two slowing down the sander gives you a little more control.

  • Tom Shap

    The only use I have found for the speed setting on my RO sander is when making stage props I often use styrofoam sheets. If I use my RO on it at full power, it will gouge the foam. If I slow it way down it sands nicely. Probably not much use unless you work with other materials than wood.

  • Al McLeod

    On occasion using very hard maple or cherry I find my Milwaukee at high speed burns the edges while the single speed DeWalt does not. I got the Milwaukee recently and before that never had a burning problem.

    Al McLeod

  • Edward Weber

    Having the ability to control the speed IMO is a positive feature. With
    every piece of wood having a different density, grain pattern, moisture
    content, etc.,why wouldn’t you change the speed? We typically sand for
    two reasons, change the shape or smooth the piece. One tool that can
    change speed for shaping and smoothing while also controlling
    overheating and clogging is what it’s all about.

  • John Schelby

    The low speed is excellent when filling fine cracks. First, I keep the almost fully used sheets until I am done with a project. When I come to a crack of any kind, I put a couple of drops of latex finish on it, turn the sander down to very low so the vacuum does not kick in sand over the crack using one of the sanding sheets I have saved. The sawdust and varnish fill the crack and readily except any stain I decide to put on it later. The sanding sheet is totally wasted after this short episode, but it was going to the trash anyway.

  • Edward Weber

    look at it this way, we sand for two main reasons. one is change the shape and the other is to smooth the surface. Having a tool that can change the speed to accommodate the differences in species, grain direction, moisture content etc, IMO is great. I change the speed depending on what I’m working on. You really can’t expect to sand soft pine with 80 grit at the same speed you would sand hard maple with 320 grit, can you?

    • Tom Conover

      So, what speed do you use for pine and what speed for hard maple?

  • Terry Wilson

    I can’t believe you pro’s missed this one. High speed will generate heat that can melt finish and load the sandpaper to the point it does more damage and smears the finish. Lower speed generates less heat and allows the paper to maintain its cutting/smoothing ability.

  • I move over the surface not too fast but quicker than Rob’s 1″ per second but move the sander in an even pattern to get a flat surface on large square surfaces and I keep it moving on longer surfaces so as not to sand in a shape that I don’t want. If I need a 60 grit I use the belt sander to start. I finish with the abranet discs as I find them quicker but remember to use the Mirka backing pads so save the sander bottom.