If you’ve ever stared at a stack of sanding discs, belts, or sheets in a hardware store and wondered why some are marked 40, others 220, and a few have random numbers like 800, you’re not alone. As someone who’s spent the last 12 years working at a coated abrasives supplier—walking customers through pickup orders, troubleshooting bad sanding jobs, and even testing grit sizes in our warehouse shop every Saturday—I get it. That number printed on the back of that abrasive isn’t just a random code your marketing team made up to confuse DIYers. It’s grit size, and it’s the single most important number that’ll make or break your sanding, finishing, or metal prep job. Let’s break this down like we would at our loading dock—no stuffy lab jargon, just real-world stuff that actually matters. Coated Abrasives
First, let’s get one myth out of the way right now: grit size isn’t “how rough the abrasive is” in a simple, one-size-fits-all way. Wait, I know—you’re thinking 40 is super rough, 220 is smooth, that’s basic, right? Sort of, but it’s way more specific than that, and the confusion starts because there are three main systems people use, which is why you’ll see two different numbers for the same size grit depending on if you’re buying for woodworking vs. metal prep. Let’s keep this simple, no acronyms that’ll make you reach for your phone to Google. The big three we deal with every day here are: the US Standard Grit (also called the ANSI system, since that’s what the American National Standards Institute updates every few years), the FEPA system (used mostly in Europe, but we get a lot of customers importing machines from Germany so we have to carry both), and the “micron” size, which is just a fancy way of saying the actual width of each grit particle, in millionths of a meter.
Let’s make this concrete, not textbook. If you pick up a 40-grit coated abrasive from our stock, that’s ANSI 40, which is basically a particle that’s around 425 microns across. For perspective, a single grain of sand you’d pick up at the beach is about 200-500 microns—so 40-grit is basically like slapping a handful of beach sand onto a flexible backing (that’s the “coated” part of coated abrasives, by the way—we glue those grit particles to a cloth or paper backing, that’s what makes discs and belts bend around corners). Then there’s 80-grit, which is about 180 microns—think fine playground sand, not beach stuff. 220-grit is like super-fine flour, around 63 microns, and 1000-grit is almost as small as a red blood cell, at 12.5 microns. That’s the micron translation, which is the only real “universal” measure, since 40-grit in ANSI is a tiny bit bigger than 40-grit in FEPA, so if you mix systems, you’ll buy something way too rough or too smooth.
Now, why does this matter to you, not just to us in the warehouse? I had a customer last month—his name was Jake, he’s a cabinet maker in Detroit—who came in panicking, yelling that his 60-grit discs were leaving way too many deep scratches on oak doors. Turns out he ordered FEPA 60 instead of ANSI 60, because he’d seen a European brand advertise FEPA grit numbers and didn’t realize they’re different. That little mix-up cost him two days of redoing doors, and he almost stopped buying from us until we showed him how to spot the system on the label (ANSI has a little “A” sometimes, FEPA has a “P” in front of the grit number—like P120 vs. ANSI 120). Moral of that story: always check the grit system, not just the number.
Another big thing most people miss: grit size works in reverse for your final finish, but it’s not linear. Let’s walk through a typical woodworking job, which is the most common use for coated abrasives that we sell. If you’re stripping an old deck, you start with 40 or 60-grit to take off all the old paint and splinters. That’s heavy material removal—you want as much grit hitting the wood as possible to grind down the rough stuff fast. Then you move up: 80-grit to smooth out the swirl marks from the 60, 120-grit to get ready for staining, 220-grit for a smooth surface before urethane. Wait, but notice the jump is smaller as you go up? That’s intentional. When you’re coarse, each jump (like 40 to 60) is a big drop in grit size (from 425 to 250 microns) so you can still knock down the leftover scratches from the previous step. But when you’re getting fine, a jump from 220 to 320 is only from 63 to 45 microns—tiny, because if you jump straight from 220 to 600, you’ll leave scratches that are way too deep, and you’ll spend 3x as much time sanding to fix them. We see this all the time—customers buy a cheap 600-grit disc for their final wood sanding, then come back complaining that their finish looks cloudy. It’s not the finish, it’s the grit size jump.
For metal workers, grit size does something totally different, which is why we have a whole separate section of our warehouse stocked with metal-specific coated abrasives. If you’re prepping a weld for painting, you start with 36 or 40-grit to grind down the weld bead and remove mill scale. Then you go to 80 or 120-grit to smooth the area so there’s no porosity in the paint. For finish work on stainless steel, you might use 220, 320, even 600-grit coated abrasives to get that mirror finish. Here, grit size matters because different metals have different hardness—harder metals like titanium need coarser grits (36-50) to cut through the surface, while softer metals like aluminum need finer grits (80-120) so you don’t clog the abrasive with metal dust. Clogging is another thing tied to grit size—coarser grits have bigger gaps between particles, so they clog less, but finer grits have tiny gaps that fill up fast with dust or resin, especially on wood or metal. That’s why we add a special coating to our finer grit abrasives (we call it “anti-clog coating” in the warehouse) that repels debris, so the grit stays sharp longer.
Wait, but what about random orbital sanders vs. belt sanders vs. hand sanding? Does grit size change for those? Absolutely. A lot of new DIYers think a 120-grit disc for a random orbital is the same as a 120-grit sheet for hand sanding, but no—because the random orbital moves in small circles, so it leaves finer scratches, meaning you can use a slightly coarser grit than you would for hand sanding, where you’re moving in straight lines that leave deeper, more noticeable scratches. If you use a 100-grit random orbital for a deck, you’ll end up with swirl marks that you have to sand out with 150-grit, but a 80-grit on a belt sander—wait no, belt sanders have a longer contact area, so they remove material faster, so you’d use a coarser grit (like 36-60) for belt sanding on decks, vs. 40-80 for random orbital. That’s another mix-up we help customers with all the time.
Let’s talk about how grit is actually made, just so you get why two 100-grit discs from different brands might feel different. We use two main abrasive minerals in our coated abrasives: aluminum oxide, which is super tough, good for wood, metal, and general purpose, and silicon carbide, which is harder and sharper, good for stone, glass, and painted surfaces. To make the grit, we take the mineral, heat it to super high temps to harden it, then crush it into tiny particles. Then we sift it through a series of screens with smaller and smaller holes—like a kitchen sieve, but industrial-sized. The particles that get caught in each screen get labeled with that grit number. For example, 40-grit particles are those that get caught on a screen with 40 holes per linear inch, so they’re between 425 and 500 microns. That’s why no two grit sizes are exactly the same—there’s a range of particle sizes in each label, which is actually a good thing, because it means the abrasive cuts faster and leaves a more even finish than if all particles were the exact same size.
Now, I know what you’re thinking: “This is great, but what grit size do I need for my specific job?” Let’s make a quick cheat sheet that we tape to our warehouse wall, because it’s the one we give every customer:
- Coarse work (stripping paint, removing heavy rust, grinding welds): 24-60 grit (ANSI)
- General sanding (smoothing wood, removing scratches): 80-120 grit
- Finish work (prepping for stain, paint, urethane): 180-320 grit
- Super fine work (buffing, mirror finishes, polishing stone/metal): 400-2000 grit
Wait, but don’t take that as gospel—always adjust for your material. If you’re sanding soft pine, go a bit finer than if you’re sanding hard oak. If you’re sanding soft aluminum, go a bit finer than if you’re sanding steel. If you’re sanding fiberglass, stick to silicon carbide grit (which is our C-grit, we mark it that way) because aluminum oxide will clog super fast.
Here’s a mistake even pro contractors make all the time: using too fine a grit for the first step. A friend of mine who’s a finish carpenter in Chicago swears he used to buy 120-grit for the first sand on cabinets, until we pointed out that 80-grit would take half the time. Now he swears by our 80-grit coated abrasive for the first pass, then moves up to 150 and 220, and he cuts his job time by almost 20%. The key is that the first grit’s only job is to remove material, not to finish—save the fine grits for the last two steps, where they smooth out the scratches from the previous coarser grit.
Another thing we deal with regularly at our coated abrasives supply: overpriced branded grit sizes. I can’t tell you how many customers come in saying they paid $20 for a 5-pack of 120-grit discs from a big box store, but they’re actually marked 150-grit in the ANSI system. We test every single batch of grit we get to make sure it matches the label, because that’s how we built our reputation 15 years ago—no misleading grit sizes, no paying for fancy branding. We’re not a big corp, we’re a small team that works with contractors and DIYers alike, and grit size is the last thing we want to mess up.
If you’re still confused about grit size, don’t overthink it. The number is a guide, not a rule. If you’re not sure which grit to use, pick a slightly coarser one than you think you need—you can always sand it smoother, but you can’t put coarse scratches back once they’re in. And always check the grit system on the label, because mixing ANSI and FEPA is the most common mistake we see.
Cutting and Grinding Wheel Making Machine At the end of the day, grit size is just a way to make coated abrasives work for you, not against you. It’s not rocket science, but it’s something you can’t afford to ignore if you want a job that looks good, gets done fast, and doesn’t cost you extra time or money to fix mistakes. If you’re working on a big project, or just need help picking the right grit size for that one tricky job (we’ve all had that one piece of wood that’s super knotty, or that weld that won’t grind), hit us up anytime. We don’t do pushy sales calls, we just send you the right abrasive, at a fair price, with the right grit size to get your job done right.
References
- American National Standards Institute (ANSI). (2018). Standard for Coated Abrasive Grain Size Designations and Test Methods. ANSI B74.15-2018.
- Federation of European Producers of Abrasives (FEPA). (2020). Coated Abrasive Grain Size Classification Standards. FEPA 42-FPA.
- Manufacturing and Technology Association (MTA). (2021). Guide to Coated Abrasive Selection for Wood and Metal Finishing. MTA Technical Report 2021-04.
iSharp Abrasives Tools Science Institute
iSharp Abrasives Tools Science Institute is one of the leading coated abrasives manufacturers and suppliers in China, now brings you the best quality coated abrasives at competitive price from its professional factory. Should you are looking for high precision and reliable performance machine, please feel free to contact us.
Address: A2507, Kai Xuan Men, Tong Bai Nan 238, Zheng Zhou, He Nan, 450006, China
E-mail: office@isharp-tools.com
WebSite: https://www.abrasives-machines.com/
