Hey everyone, I’m Jake, and for the last 7 years, I’ve been working at a ball bearing disc spring supplier—you know, the guys who make those tiny, curved steel discs that handle load, absorb shock, and keep all kinds of machinery running smooth. These little things might look simple, but let me tell you, if you get their measurements even a tiny bit off, you’re not just selling a part—you’re risking a customer’s entire assembly. Last quarter, a customer reached out panicking because their 8mm disc spring was 0.02mm thinner than the spec they sent, and their entire conveyor line was shutting down. That’s why I want to break down how we measure ball bearing disc springs accurately—stuff we’ve learned on the job, not just textbook jargon, so you don’t run into that headache. Ball Bearing Disc Spring
First off, let’s get on the same page about what we’re actually measuring here. A ball bearing disc spring isn’t a flat washer, right? It’s a conical disc, so there are a few key dimensions that matter more than others. The main ones are outer diameter (OD), inner diameter (ID), thickness, and free height. Wait, you might be thinking, “Why not just measure height?” Because it’s not straight—when it’s stacked with other disc springs, that free height (the height before any load is applied) changes, and if your measurement is off, the stack won’t sit right. Those tiny specs add up fast. At our shop, we deal with everything from micro-disc springs for medical devices that are barely 2mm across to heavy-duty ones for construction that top 100mm. Each size needs a different approach, but there are core steps that work for all.
Let’s start with the basics: pre-measurement prep. I can’t tell you how many times I’ve seen a tech grab a disc spring right off the production line, covered in light oil or tiny metal shavings, and hop on a caliper. That’s a rookie move. If there’s oil on the surface, the caliper’s jaws will glide a little, leading to wonky numbers. Metal shavings can get caught between the disc’s surface and the measuring tool, adding 0.01mm or more to your reading—nothing to sneeze at when the spec is ±0.02mm. So first, clean the disc gently. We use lint-free microfiber cloths and isopropyl alcohol (the 90%+ kind, not the cheap 70% stuff that leaves streaks) for high-precision parts. For really tiny ones, we’ll blow them off with compressed air filtered to 0.2 microns—we learned that after a batch of 3mm medical disc springs got a shavings stuck, and we had to scrap 500 parts. Ouch.
Also, let the disc springs acclimate to the room temp before measuring. Steel expands and contracts, duh, but if you just brought a fresh batch from the 70°F production floor into a 68°F measuring room, that 2-degree difference might not sound like much, but for a 50mm OD disc, that’s a 0.008mm shift—again, enough to make a customer reject a full shipment. We leave our parts in the measuring area for at least 2 hours before we check them, and we log the room temp every day—simple step, but it’s saved us so many errors.
Now, the actual measurements. Let’s go one by one, starting with outer diameter (OD). At first glance, OD seems easy—just clamp a caliper around the outside and take a number. But wait, disc springs aren’t perfect circles, right? Stamping and forming can leave tiny variances around the edge. If you only measure at one point, you could get a number that’s off by 0.03mm, which is a huge deal. What we do here is use a digital outside micrometer for most sizes, not a caliper. Micrometers are precise down to 0.001mm, and they lock in the reading so you don’t fumble it. But even with a micrometer, you need to take 8 measurements, spaced 45 degrees apart around the disc. We mark a tiny dot on the first point, then rotate the disc a little each time, so we cover the entire circumference. For example, a 20mm OD disc gets measured at 8 spots, and we average those numbers—if the average is within ±0.01mm of the spec, it passes. I know that sounds overkill, but one time we had a batch where one spot was 0.04mm too big, and the rest were spot on. We almost shipped them until we double-checked, and that one outlier would’ve caused a press to jam. We don’t want that on our hands.
Next up, inner diameter (ID). This is trickier because ID is the hole in the middle, and if the edges of the hole aren’t smooth, the jaws of a caliper can slip. For ID, we use either a digital inside micrometer (the kind that looks like a long rod with a measuring tip) or, for smaller holes, bore gauges. Bore gauges are great because they self-center in the hole, so you don’t have to guess if you’re measuring straight across. Same rule as OD: take 8 measurements, average them, and make sure none of them are more than 0.015mm off spec. We had a customer a while back who needed ID within 0.01mm for a ball bearing press, and we almost missed that because a tech only took one ID reading. The disc was slightly egg-shaped, and the average ID was perfect, but the one spot he measured was 0.02mm too small. We fixed that, of course, but it made us swear off single-point measurements forever.
Now thickness. This might be the most critical dimension for disc springs, because thickness directly correlates to load capacity. If your disc is 0.05mm thinner than spec, it can handle 10% less load, which means the customer’s product won’t hold up. We use a flat anvil micrometer for thickness—important, not a pointed one. A pointed anvil will dig into the steel and give a false thick reading. We lay the disc flat on the anvil, clamp the micrometer gently (not super tight, that compresses the steel and makes it read thin), and again take multiple measurements. Wait, why multiple? Because the edges of the disc are usually a tiny bit thicker than the center, or there might be a burr from stamping. We measure at the outer edge, halfway between outer and inner, and the inner edge—three points—so we catch any thickness variances. For micro disc springs, we use a laser thickness gauge. It’s non-contact, so no risk of scratching the delicate disc, and it measures 100 points in a fraction of a second. That’s a game-changer for small parts.
Then there’s free height, the one that trips up a lot of people. Free height is the total height of the conical disc when it’s not under any load—this determines how much deflection you’ll get when you stack them. Measuring this wrong is such a common mistake. A lot of guys just plop the disc on a flat surface, stick a ruler on top, and call it a day. That’s garbage because the disc is curved, so if you press too hard with the ruler, you flatten it, or if you tilt it, you get a wrong height. What we use here is a height gauge with a straight, flat contact foot—think of it as a precision ruler that lowers straight down. We place the disc on a granite surface plate (super flat, no warping, perfect for measurements), then lower the contact foot slowly until it just touches the highest point of the conical disc. No pressing down—just light contact. We take that reading, then flip the disc over and measure the other side to make sure we didn’t get a wonky spot. For stacked disc springs, we measure the total stack height too, same way—lay it on the plate, measure from the bottom of the bottom disc to the top of the top one, light contact only.
Wait, should we talk about tools vs. hand measurements? A lot of small suppliers or hobbyists might not have access to a million-dollar laser gauge, so what can they do with basic tools? First, if you’re using calipers, make sure they’re calibrated. Calipers get out of whack all the time—if you drop them, the jaws can shift. Calibrate them against a gauge block every week, or even every day if you’re using them non-stop. For ID, if you don’t have an inside micrometer, you can use outside calipers, but you have to adjust them until they fit snuggly in the hole, then measure the distance between the caliper’s jaws with an outside micrometer. It’s less precise, but it works if you don’t have other tools. And for free height, if you don’t have a height gauge, a digital ruler that has a flat bottom and can measure in 0.001mm increments works—just make sure it’s sitting straight, not tilting.
Also, a quick note about common mistakes we see customers (or even other suppliers) make. First, using worn tools. If your micrometer’s anvil has scratches or rust, that’s going to give bad readings. We calibrate all our measuring tools once a month by a third-party lab—no exceptions. Second, ignoring the shape of the disc. Like I said, disc springs aren’t perfect circles, so single-point measurements are almost always wrong. Third, rushing. We had a batch of 1000 disc springs that we almost shipped because a trainee was measuring too fast and missed a 0.03mm OD variance on half the parts. We caught it during a double-check, and we made the trainee stay and measure every part slow. It’s tedious, but it’s worth it.
At the end of the day, accurate measurements aren’t just about following a checklist—they’re about ensuring your ball bearing disc spring works exactly as it’s supposed to. Whether it’s for a car’s braking system, a medical implant, or a construction machine, that small disc has to perform under pressure, and if its dimensions are off, everything downstream suffers. If you’re a parts designer, a procurement manager, or even a hobbyist looking for reliable disc springs that meet exact specs, we’ve got you. We don’t cut corners on measurement, and we stand behind every part that leaves our shop. If you need to run a spec by us, ask about testing, or place an order, reach out—we’re here to make sure you get the right disc springs, every time.
TREP French Spring Washers References:
- Machinery’s Handbook, 31st Edition, Industrial Press Inc., 2020, pp. 1872-1885.
- ASME B46.1-2019, Surface Texture, American Society of Mechanical Engineers, 2019.
- ISO 7086-1:2018, Rolling Bearings – Disc Springs – Part 1: Metric Series, International Organization for Standardization, 2018.
Yangzhou Optimum Spring Manufacturing Co., Ltd.
As one of the most professional ball bearing disc spring manufacturers and suppliers in China, we’re featured by quality products and good service. Please rest assured to buy customized ball bearing disc spring made in China here from our factory. For more information, contact us now.
Address: No.9 West of Shuangtang Rd, Yangzhou, P.R. China 225000
E-mail: susie@optimum-spring.com
WebSite: https://www.optimum-spring.com/
