Which Is Better, Ball Bearing or Roller Bearing? A $4,300 NSK Bearings Mistake

In September 2022, a maintenance manager asked me a question I'd answered dozens of times: "Which is better, ball bearing or roller bearing?" I gave him a quick answer. That quick answer turned a $1,400 bearing order into a $4,300 lesson.

I handle replacement bearing orders for a small automation supplier that's an authorized NSK distributor. Seven years in the job (since 2018, actually), and I've made my share of mistakes—I've documented most of them. This one is the one that made me change how I quote.

The question that seemed simple

The customer was rebuilding a linear electric actuator from a food packaging line. The actuator's motor was fine, but the bearing at the end of the ball screw was failing. They needed replacements in a hurry.

Their lead tech called and asked: "which is better ball bearing or roller bearing?" I said ball bearings are more versatile, easier to source, and usually fine for moderate loads. That statement, by itself, isn't wrong. But I didn't ask what "moderate" meant in their machine.

We stock NSK bearings across the lineup, and we carry NSK radial and deep groove ball bearings as a default. The sizes matched the old part numbers. The price looked good. I sent a quote with 16 bearings, they approved it, and we shipped the same day.

I also remember the mention of stainless steel ball bearings. The line gets washed down every night. But I assumed standard steel would be fine because the existing bearings weren't rusty. I didn't stop to think that corrosion wasn't the issue—load was.

Three weeks later

The call came on a Wednesday morning. The actuator had seized mid-cycle. They had a full line stopped and a maintenance crew standing around.

The failure was not subtle. When our technician opened the actuator, the grease smelled burnt and looked like silver paint. The raceways on two of the deep groove ball bearings were spalled. Metal flakes everywhere. No one was hurt (thankfully), but the line was down for two days.

We had shipped those bearings. The part numbers were right. The size was right. The load rating was wrong.

That's when I learned to ask a different question, one I now ask before any price conversation: "What's NOT included?" In this case, what wasn't included was any engineering review of the application. The original quote was transparent about the bearing price. It wasn't transparent about the missing load check. I hadn't charged for it, so I hadn't done it.

A vendor who lists all fees upfront—even if the total looks higher—usually costs less in the end. I didn't do that.

The repair

We replaced all 16 bearings with the correct set. For the two heavily loaded positions, that meant NSK precision bearings in a cylindrical roller design. The rest stayed as deep groove, because they truly were moderate-load positions. Same actuator, same fit, same speed—different bearing type.

NSK's rolling bearing catalog (as of January 2025, at least) puts it plainly: cylindrical roller bearings are designed for heavy radial loads; deep groove ball bearings take moderate radial loads plus some axial load in both directions. I knew that. I just didn't apply it.

The replacement bearings cost more. The overnight shipping cost more. And the real bill was the customer's downtime, not ours. But we covered the second set and the technician time, so yes, the mistake had a dollar figure on our side: roughly $4,300 when you add the failed components, labor, and freight.

Ball bearing vs roller bearing: what I say now

When someone asks "which is better, ball bearing or roller bearing?", my answer is: it depends on the load. Then I ask:

1. What direction is the load? Radial, axial, or a combination?
2. How heavy is it relative to the bearing size?
3. What's the shaft speed range?

If the load is mostly radial and heavy, choose a roller bearing. If it's a mix of moderate radial and axial loads, and speed is a factor, a deep groove ball bearing is usually the better starting point. What I mean is that "ball bearing or roller bearing" is not a preference question, and by that I mean you have to know the bearing's exact job before you can answer honestly.

Defaulting to the most common type is tempting. NSK radial and deep groove ball bearings are used in countless machines for good reasons: low friction, high speed capability, and reasonable price. But "common" isn't the same as "correct."

The part I still think about

The customer had asked about stainless steel ball bearings on that first call. They were right to think about corrosion. If we'd sent stainless steel ball bearings, the machine might have survived longer. But it still would have failed, because the bearing type didn't match the load.

There's something satisfying about seeing the corrected actuator run smoothly. After the embarrassment, the rework, and the paperwork, finally it ran a full night shift without a single alarm. That's the payoff.

I still document my mistakes. I still maintain our team's checklist. It starts with the same three words: open the manual. The bearing number, the actuator drawing, and the load direction are all in there. I just needed to look before I answered.

My experience is based on roughly 200 replacement-bearing orders, mostly for machinery in food and packaging plants. If you're working on high-speed spindles, submersible equipment, or anything with shock loads, this isn't enough—get an engineer and a proper bearing calculation. But for a linear electric actuator under normal loads, the process is simple: check the load, then check the bearing type, then check the price.