I handle purchasing for a 140-person manufacturing plant. Since 2021, I have managed roughly $180,000 per year in MRO spend across nine vendors. I do not design the machines here—that is not my job. But I am the person who turns a maintenance request into a purchase order, and bearings are the item that creates the most “are you sure?” phone calls.

This is the SKF bearings FAQ I wish I had when I started. If you are looking for pillow block bearings, trying to understand thrust bearings, or comparing steel ball bearings, the answers below are what I actually use on the plant floor.

  • How do I tell SKF bearing types apart?
  • What are SKF pillow block bearings used for?
  • Which steel ball bearings should I keep in stock?
  • When does a spherical roller bearing make sense?
  • What’s a thrust bearing?
  • Why would I need a linear actuator control kit?
  • When is paying extra for faster bearing delivery worth it?

How do I tell SKF bearing types apart?

Most people assume SKF bearings are one product family, but it’s really a set of load-handling designs. The fastest way to make sense of them is to ignore the part numbers for a moment and look at the load direction.

A radial load is perpendicular to the shaft. That is what a deep groove ball bearing handles best, which is why it’s the default steel ball bearing for fans, pumps and simple conveyors. Heavier radial loads usually point you toward cylindrical or spherical roller bearings. An axial load runs along the shaft, and that is the territory of thrust bearings.

Once you know radial vs. axial, a bearing catalog stops looking like a wall of numbers. You still need to confirm bore size, seals, clearance class and speed limits, but load direction is what gets you to the right family.

What are SKF pillow block bearings used for?

A pillow block bearing—also called a plummer block—is a bearing, housing, seals and mounting base in one ready-to-bolt assembly. It is the option you choose when a shaft has to be supported on a frame but you don’t want to machine a precision bore into the frame itself.

At our plant, we use them on conveyor line shafts, fans and light-duty idlers. The housing does the alignment work for you, and it protects the rolling elements from dust and drips. For heavier line shafts, we move to split housings with spherical roller bearings inside; for lighter positions, the typical SKF pillow block unit is a Y-bearing mounted in an SY-style housing.

The buying mistake I see most is ordering a replacement by an old label alone. When a pillow block fails, measure the shaft diameter, the housing centre height and the bolt hole spacing. Those three dimensions catch more specification errors than reading a worn nameplate ever will.

Which steel ball bearings should we stock?

When someone in our maintenance team asks for “steel ball bearings,” they usually mean deep groove ball bearings with steel balls—chrome steel, in most industrial cases. The most common series for general equipment are the 60 and 62 series because they cover the shaft sizes found in pumps, fans, gearboxes and conveyors.

We keep a small stock of 6000, 6202, 6204 and 6205 sizes. The default for us is the 2RS sealed version because contamination is our biggest bearing killer. Or rather, we keep sealed versions for dirty areas and shielded versions for positions that run a little hotter and need lower drag.

One thing I learned the hard way: never order by “25 mm ball bearing.” You need the full designation. A 6205-2RS/C3 is not the same as a 6205-ZZ or an open 6205, even though they all fit the same shaft. It took me about 40 orders—and one very annoyed maintenance supervisor—to understand that suffixes like 2RS, ZZ and C3 are not optional extras.

When do I need a spherical roller bearing?

If someone types “spherical roller bearings SKF” into a search engine, they usually have one of two problems: a heavy radial load or a shaft that cannot stay perfectly aligned with its housing. A spherical roller bearing uses two rows of rollers guided by a common sphered raceway in the outer ring, so it can self-align under shaft deflection or housing misalignment.

Typical applications include crushers, vibrating screens, heavy fans and conveyor drive shafts. For a lightly loaded machine running in perfect alignment, a deep groove ball bearing is the simpler and often more economical choice. But when loads are high and the frame flexes, a spherical roller bearing is usually the answer.

When you ask a supplier for a quote, give them the full designation, not just the series. For example, a code like 22220 E/C3 tells them the bore, the width series, the increased load capacity and the internal clearance. If you only say “spherical roller bearing, shaft is about 100 mm,” you will get a phone call back asking for the same information anyway.

What’s a thrust bearing?

A thrust bearing is a bearing designed mainly for axial load—that is, load pushing along the shaft rather than perpendicular to it. A vertical pump impeller pushes downward when it runs. A machine spindle experiences axial force during drilling. Boats and ships have thrust bearings on propeller shafts. In each case, the bearing’s job is to keep the shaft from moving forward or backward.

Thrust bearings come in several styles. Ball thrust bearings handle lighter loads and moderate speeds. Cylindrical roller thrust bearings are for heavier axial loads. Spherical roller thrust bearings are for the heaviest applications where alignment is also a concern. There are also angular contact ball bearings, which handle a combination of radial and axial loads in one unit.

The easiest confusion to clear up: a thrust bearing is not just a thick washer. It has rolling elements running between raceways, and it is not designed to support a radial load on its own. If the application needs both, you either pair it with a radial bearing or use a type that handles both directions.

Why would I need a linear actuator control kit?

This question comes up almost every time we automate a small motion on a packaging line. A linear actuator is the mechanical part: it turns motor rotation into straight-line movement. But you still need something to tell it where to stop, when to reverse and what to do at the end of the stroke.

A linear actuator control kit usually bundles the controller, limits and cabling into one set. Our first actuator purchase in 2023 did not include the control kit, and the quote looked great. Then the electrician had to build a reversing circuit with separate limit switches. The labour cost more than the control kit would have, and we lost a day of commissioning time.

Now I treat the linear actuator control kit as part of the system, not an add-on. The question I ask before ordering is: does this include the controller, the hand pendant, the cable lengths and the limit function we need? For both SKF actuator systems and other vendors, the complete package is what saves the unnecessary second purchase.

When is paying extra for faster bearing delivery worth it?

It’s tempting to always pick the cheapest shipping option, but bearing failures rarely wait for standard lead times. Last year, our feed conveyor went down on a Thursday afternoon. The bearing itself was not expensive. What mattered was that the line was scheduled to run on Friday morning.

We paid an expedite fee for one reason: certainty. The lower-cost option came with “probably Friday” or “maybe early next week.” That answer was not good enough when every hour of downtime had a real number attached to it. The fee bought us a confirmed dispatch date, which is exactly what a maintenance emergency needs.

I don’t think every order should be expedited. But when there is a deadline, uncertainty has a cost. Ask a supplier whether the stock is actually on the shelf, what the order cut-off time is, and whether they can commit to a dispatch date in writing. A cheap delivery promise that cannot be confirmed is not cheaper at all.