Self-aligning Ball Bearings 1218M 2218M 1318M

The 1218M, 2218M and 1318M are double-row self-aligning ball bearings with a 90 mm bore.

At first glance, these three models are quite similar. They are all made for a 90 mm shaft, but the outside diameter and width are different. This is something worth checking before placing a replacement order.

The 1218M measures 90 × 160 × 30 mm, while the 2218M has the same bore and outside diameter but is 10 mm wider. The 1318M is larger, at 90 × 190 × 43 mm.

The self-aligning design comes from the spherical raceway on the outer ring. It allows the bearing to accommodate a small amount of shaft-to-housing misalignment. This can be useful when the shaft or housing is not perfectly aligned during operation.

For most standard orders, the model number is enough. If you are replacing an old bearing and the marking is no longer readable, the bore, outside diameter and width are the three measurements we would check first.

This is probably the first thing to check when selecting one of these bearings.

All three have a 90 mm bore, but their dimensions are different.

1218M - 90 × 160 × 30 mm

This is the narrowest one.

If the bearing space is limited in the axial direction, the 30 mm width may be important.

2218M - 90 × 160 × 40 mm

The bore and outside diameter are the same as 1218M.

The difference is the width:

1218M → 30 mm

2218M → 40 mm

So these two should not be treated as interchangeable without checking the available space.

1318M - 90 × 190 × 43 mm

1318M is larger in both outside diameter and width.

It needs a different housing space from the 1218M and 2218M.

If you are replacing an old bearing, match all three dimensions rather than checking the bore only.

A normal bearing expects the shaft and housing to stay reasonably aligned.

In real machinery, this is not always easy.

The shaft can move slightly.
The housing can be machined with a small error.
The frame can also deform under load.

The spherical outer raceway of a self-aligning ball bearing gives the bearing some freedom to adjust to these small changes.

This is the main difference between this bearing and a standard deep groove ball bearing.

It is worth noting that **self-aligning does not mean unlimited alignment**. A large shaft or housing error still needs to be corrected during installation.

The basic construction is fairly simple:

Outer Ring → Steel Balls → Cage → Inner Ring

There are two rows of balls inside the bearing.

The outer ring has a curved raceway. This curved surface is what allows the bearing to adjust when there is a small angular difference between the shaft and housing.

The two-row arrangement also gives the bearing a good radial load capacity for its size.

When replacing a bearing, buyers sometimes focus on the bore and outside diameter and forget about the width.

That can cause problems.

Take 1218M and 2218M as an example.

Both are:

90 mm bore × 160 mm OD

But:

1218M = 30 mm wide

2218M = 40 mm wide

The extra 10 mm may affect the position of nearby components, shaft shoulders, spacers or retaining parts.

So when checking an old bearing, measure:

d + D + B

not just d.

The internal clearance is another point that should not be ignored.

The available options include C0, C3 and C4.

C3 and C4 are not simply "better" versions.

Higher clearance can be useful when the bearing operates at higher temperatures or when the shaft fit causes the internal clearance to reduce during operation.

For a normal machine running at moderate temperature, standard clearance may be enough.

If you are not sure, it is better to provide the shaft fit, temperature and speed before choosing the clearance.

The cage keeps the balls separated and helps guide them during rotation.

A steel cage is a common choice for standard applications.

Brass cages can also be considered when the working conditions require a different cage design.

The cage should be selected together with the speed, load and lubrication conditions.

The 1218M, 2218M and 1318M range can be supplied in different configurations.

An open bearing is easier to inspect and relubricate.

A 2RS version has rubber seals on both sides and provides better protection against normal dust and contamination.

The choice depends on the machine.

Do not choose a sealed version only because it sounds more protective. Make sure the seal type also fits the operating speed and temperature.

If you have an old bearing and want to identify the replacement, you can start with three measurements.

1. Bore - d

Measure the hole through the center.

For these models:

d = 90 mm

2. Outside Diameter - D

Measure across the outside of the outer ring.

1218M = 160 mm

2218M = 160 mm

1318M = 190 mm

3. Width - B

Measure the total bearing width.

1218M = 30 mm

2218M = 40 mm

1318M = 43 mm

These three numbers usually give you a good starting point for identifying the correct model.

Mistake 1: Choosing only by shaft diameter

A 90 mm shaft does not mean 1218M, 2218M and 1318M are interchangeable.

Mistake 2: Ignoring bearing width

A 10 mm difference can be enough to prevent installation.

Mistake 3: Using the wrong clearance

C3 should not be used simply because the machine is "heavy duty."

Mistake 4: Ignoring the shaft condition

A new bearing cannot compensate for a damaged shaft.

Mistake 5: Assuming self-aligning means no alignment is needed

The bearing can handle limited misalignment. It cannot correct a badly installed shaft.

Q1: What is the difference between 1218M, 2218M and 1318M?

The biggest difference is the bearing size.

1218M and 2218M both have a 90 mm bore and 160 mm outside diameter. The difference is their width: 30 mm for 1218M and 40 mm for 2218M.

1318M is larger, measuring 90 × 190 × 43 mm.

So if you are replacing one of them, don't select the new bearing based only on the shaft diameter.

Q2: Can I use 2218M instead of 1218M?

Not in every case.

The two bearings have the same bore and outside diameter, but 2218M is wider. If there is enough space around the bearing, it may be possible, but the complete bearing arrangement needs to be checked first.

For a direct replacement, we recommend keeping the original model.

Q3: What does the self-aligning function actually do?

It allows the inner ring and rolling elements to adjust slightly inside the outer ring.

This is useful when there is a small difference between the shaft and housing alignment.

It is not a way to fix a badly bent shaft or a poorly made housing.

Q4: All three bearings have a 90 mm bore. Why can't I use any of them?

Because the bore is only one part of the bearing size.

The outside diameter and width also have to fit the machine. For example, a 1318M has a 190 mm outside diameter, so it cannot simply replace a 1218M in a 160 mm housing.

Q5: Which clearance should I choose, C0 or C3?

For a normal operating condition, standard clearance is often used.

C3 gives more internal clearance and may be considered when the bearing is subject to higher temperature or certain shaft fits.

There is no need to choose C3 just because the machine is large or the bearing is expensive. The actual working conditions matter more.

Q6: Can these bearings be supplied with C4 clearance?

Yes, C4 is also available for the listed bearing range.

If you need C4, please mention it when requesting a quotation so the exact specification can be confirmed before production.

Q7: Are 1218M, 2218M and 1318M open bearings?

The range can be supplied in different configurations. Open and sealed versions are available depending on the exact model and specification.

If your existing bearing has a seal, it is better to provide the complete bearing number when ordering.

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