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Those who have used a Sander may have encountered the same situation: sanding with the coarsest grit until the surface appears smooth, then immediately switching to a very fine grit to save time, only to end up having to start all over again because new scratches appear that just won't sand out.
The subsequent question is: when using a sander, do you really have to progress grit by grit sequentially? How many grits can you skip? And if you do skip, how do you know if you are actually slowing yourself down instead of speeding up?
The general rule in woodworking is to skip no more than one step in the standard grit sequence. The reason stems from the function of each sandpaper grit: the next grit is responsible for removing the scratches left by the previous one. If you skip too far ahead, the finer grit won't remove enough material to erase the coarser scratches, even with a sander. This causes you to spend several times longer on that grit than you should, and is yet another sanders failing to produce a smooth finish problem, aside from using the wrong type or operating the tool incorrectly.
Sanders don't smooth out; they replace existing scratches.
The understanding that changes how you work with a sander the most is realizing that sanding isn't gradually making a surface smoother and smoother; it is replacing larger scratches with progressively smaller scratches, step by step.
Looking at it this way, you'll immediately understand why skipping too many grits doesn't save time, and why sometimes, even after sanding for a very long time, the surface still doesn't turn out as good as expected.
Every grit always leaves scratches.
Why sandpaper that cuts fast might not be the choice that gets the job done faster? Coarse grit sandpaper removes material quickly because of its large abrasive grains, but the scratches it leaves behind are correspondingly deep. In contrast, fine grit sandpaper removes material more slowly and leaves shallower scratches. Therefore, a surface that looks smooth to the naked eye still always has scratches—they are just too small to be seen in normal light, but will reveal themselves under raking light or once a finish soaks in.
The next grit must cut deeper than the previous scratches
The next sanding stage succeeds only when it cuts deep enough to completely remove the bottom of the scratches left by the previous grit. If you jump from a very coarse grit straight to a very fine grit, the smaller abrasive particles will take a tremendously long time to remove those deep scratches, and workers often give up beforehand, leaving scratches that show through once the finish is applied.
The time wasted from skipping grits isn't immediately obvious, but it gets spread out in the form of spending far longer on the final grit—leading workers to assume they don't know how to sand or that the sander isn't powerful enough.
A practical grit sequence for sanders
The grit sequence you should use isn't as rigid as the principle behind it, but there are practical guidelines suitable for most jobs—basing your choice on the initial surface condition rather than simply grabbing the coarsest grit available.
What you need to answer before picking up the first sheet is: what's wrong with the current surface? That answer dictates which grit to start with on your sander, and starting at the wrong point is what drags out the work before sanding even begins.
Start with the grit that solves the problem, not the coarsest grit
If the surface has deep gouges, planer marks, or needs leveling, start with a coarse grit. If the wood has already been planed smooth and only requires surface prep before painting or finishing, starting with too coarse a grit may only create more work by forcing you to sand out newly created coarse scratches.
Skip no more than one grit step
Standard commercially available grit sequences are designed with appropriate intervals: the next grit can still cut away enough material to remove the previous grit's scratches in a reasonable amount of time. Skipping one step is acceptable on surfaces that are already in good shape, but skipping two or more steps can drastically increase the time spent on the target grit.
Which grit to stop at depends on what comes next
There is no single final grit number for sanders that fits every job. If you plan to paint over it, sanding too fine makes the surface too slick for paint to adhere properly. But if you are staining or applying oil, the surface needs to be finer, as scratches show more prominently once the finish penetrates the wood grain. Therefore, asking what the next step is serves better than memorizing a fixed formula for every project.
Use a sander without wasting time: check whether the current grit is finished
A sander issue encountered even more often than skipping grits is switching grits before the current one has finished its job—which yields the exact same result as skipping grits, except you mistakenly believe you followed the proper sequence. However, there is a method that takes under a minute and virtually eliminates this problem using things already available on-site without buying anything extra.
Shine a light at an oblique angle across the workpiece
- Hold a flashlight or work lamp at an angle across the surface rather than shining it straight down.
- Sanding scratches that are invisible under normal lighting will immediately stand out as distinct lines.
- If scratches from the previous grit are still visible, it means you shouldn't switch grits yet.
- This method can also be used for final quality inspection before delivering to customers, as it mimics the raking light angles customers will see when placing the workpiece near a window.
Use pencil guide marks
Lightly draw pencil lines across the entire surface before moving to the next grit, then sand until all pencil marks disappear completely. This method tells you two things simultaneously: whether you've sanded long enough, and whether you've sanded thoroughly. Any remaining pencil marks show where the sander hasn't passed over yet, or passed without enough pressure—a common problem found along edges and corners of the workpiece.
What happens when you skip grits, based on the finished work?
The consequences of skipping grits usually don't appear right after sanding, but show up in subsequent stages, making them hard to fix and wasting far more time because you have to redo work you thought was already finished.
Common symptoms of skipping grits often get mistakenly blamed on the finish or the sander, rather than tracing back to the sanding process itself.
Scratches appearing during finishing
Wood that looked smooth when dry immediately reveals sanding scratches once stain or oil is applied, as the finish penetrates deeper into the grooves than the surrounding surface, leaving darker lines than the rest of the grain. Fixing this requires sanding off the finish and starting almost entirely over—wasting far more time than progressing through all the grits in the first place. On high-priced lumber, this also risks reducing workpiece thickness beyond the specified design.
Uneven surface texture
Some spots feel smooth while others feel rough because the finer grit failed to completely remove previous scratches, even when using a sander. This condition is obvious when felt with bare hands but difficult to spot visually, so it can slip past the maker's inspection all the way to the customer. It becomes one of the hardest complaints to argue because both parties can feel it, but neither can pinpoint the exact flaw.
Spending more time with the sander without realizing it
The time you thought you saved by skipping grits is usually eaten up by sanding with the final grit much longer than usual. If you have to backtrack and start over, the total time ends up significantly longer than properly progressing through the grits. This is most noticeable in repetitive, multi-piece work, where the extra time per piece multiplies across the entire batch.
Abrasives that haven't lost sharpness, but can no longer work
Another reason people mistakenly think they need to switch grits when they should actually just replace the sanding sheet is that the abrasive surface has become clogged and stops cutting—even though it still looks new from the outside.
When wood dust and resin clog between abrasive grains, the paper simply glides over the surface instead of cutting material away. Aside from failing to make progress, using it with a sander also generates heat that can burn the wood. This is detailed in the article Loading, Glazing, and Dulling as previously explained.
The easiest way to tell is if you have to apply more downward pressure on the sander than when you started to get the same result: that means it's time to change the sheet, not the grit. Forcing extra pressure only leads to further problems.
Pressure and feed speed of the sander affect the remaining scratches
Both factors impact results just as much as grit selection, but many people overlook them because they aren't things you can purchase or compare on a box label. What both have in common is: the more you try to rush using these shortcuts, the slower your overall progress becomes, because you'll have to fix the defects in the next step.
Pressing harder on the sander doesn't mean faster work
Especially with random orbital sanders, excessive pressure stops the sanding pad's free rotation, leaving only fixed-pattern vibration. This creates swirl marks that are much harder to remove—and these are the exact marks that most frequently show up once you apply a finish.
Moving the sander too fast results in uneven sanding.
If you move the machine too fast, each spot will be sanded unevenly, leaving patches of scratches that aren't visible while sanding. The method that yields the most consistent result is move slowly and overlap each pass by about half the width of the sanding disc, and let the weight of the tool do the work instead of applying downward pressure.
The edges of the workpiece provide minimal support. Allowing more than half of the sander to hang over the edge will cause it to dig deeper into the edge, creating a rounded edge that becomes most apparent when assembling the pieces.
Conclusion
Progressing through grits isn't just an arbitrary routine; it's a logical sequence where each grit is designed to remove the scratches from the previous one. Skipping too far ahead doesn't save time—it merely shifts all the work to the final grit, and sometimes even moves the problem to the finishing stage, where it's much harder to fix.
Remember to start with the grit that solves the surface's current condition, skip no more than one step, and inspect with raking light or pencil marks before changing grits every time.
Checking takes only a few extra minutes per job, but it eliminates scratch marks from Sander showing up during the finishing phase—a problem that is always more expensive to fix later, whether measured in lost time or wasted material.