Pillow Block vs Plummer Block: Are They The Same?

When searching online or discussing pillow blocks and plummer blocks with different suppliers, you may be told that they are the same and that the two terms can be used interchangeably. However, in many industrial applications, pillow blocks and plummer blocks refer to different things.

They may differ in housing design, internal bearing type, functions, and suitable applications. To help you understand these differences clearly, this article explains their key differences here.

After understanding the differences, you can determine whether you need a pillow block or plummer block. If you need to purchase these products, you can contact BKZ Industry, a bearing manufacturer with more than 15 years of experience in bearing units and bearing housings. Simply send us the bearing model, required quantity, dimensions, operating conditions, and drawings if available. Our team will check your requirements and provide a quotation promptly.

Before comparing pillow blocks and plummer blocks in detail, you should first understand what each one is.

Part 1. Pillow Block vs Plummer Block: What They Are?

A pillow block is a bearing housing with a pedestal-shaped structure, a flat mounting base, and usually two bolt holes, one on each side. The center of the housing is raised and rounded to hold the bearing, while the shaft passes horizontally through the bearing bore. When checking the size chart, pillow block bearing units are commonly listed in the UCP series.

So, what is a plummer block? In appearance, it is similar to a pillow block. A plummer block also has a pedestal-shaped housing, a flat mounting base, two bolt holes, and a raised center section that holds the bearing. The main structural difference is that a plummer block usually has a split housing. When choosing from the size chart, plummer block housings are commonly listed in the SN series and SD series.

Part 2. Pillow Block vs Plummer Block: Design

From the definitions above, you can see that UCP-type pillow blocks and SN- or SD-type plummer blocks have similar pedestal-shaped appearances, but their housing structures and bearing arrangements are different.

In general, a UCP-type pillow block has a one-piece housing, while an SN- or SD-type plummer block has a split housing consisting of a separate cap and base.

When comparing products for similar shaft diameters, SN- and SD-type plummer blocks are generally larger and more robust than standard UCP pillow block units.

They also differ in their shaft-locking methods. A standard UCP pillow block unit normally uses set screws located on the extended inner ring of the insert bearing to secure the bearing onto the shaft. In a plummer block arrangement, the bearing may be mounted directly onto a cylindrical shaft with an appropriate shaft fit, or a tapered-bore bearing may be mounted onto the shaft using an adapter sleeve or withdrawal sleeve.

Part 3. Pillow Block vs Plummer Block: Bearings Inside

In addition to their design differences, pillow blocks and plummer blocks generally use different types of bearings. A UCP-type pillow block normally uses a UC-series insert ball bearing. This bearing has a spherical outer surface that allows it to self-align within the housing and an extended inner ring with set screws for securing it to the shaft.

In comparison, SN- or SD-type plummer block housings commonly accommodate separate self-aligning ball bearings or spherical roller bearings.

Part 4. Pillow Block vs Plummer Block: Functions

Because pillow blocks and plummer blocks differ in their housing designs and internal bearings, they also have different load-carrying capabilities, installation features, and suitable operating conditions.

Key Functions of Pillow Block Bearings:

• Support rotating shafts and primarily carry radial loads.
• Carry limited axial loads in both directions through the insert ball bearing.
• Provide limited self-alignment between the insert bearing and housing to accommodate initial mounting misalignment.
• Provide a ready-to-install and cost-effective bearing solution for general-duty machinery.

Key Functions of Plummer Block Bearings:

• Make housing installation, inspection, lubrication, and maintenance easier because the housing cap and base can be separated.
• Carry high radial loads when fitted with spherical roller bearings.
• Carry combined radial and axial loads when fitted with a suitable locating spherical roller bearing or self-aligning ball bearing
• Accommodate angular misalignment when fitted with a self-aligning ball bearing, spherical roller bearing.
• Support locating and non-locating bearing arrangements. A locating bearing controls the shaft position axially, while a non-locating bearing allows axial displacement caused by shaft thermal expansion.

Part 5. Pillow Block vs Plummer Block: Applications

With these differences in functions and designs, pillow blocks and plummer blocks are suitable for different applications.

Pillow Block Applications

UCP-type pillow block bearing units are suitable for light- to medium-duty equipment that requires simple installation, compact construction, and economical shaft support.

Here are the major applications in which they are used:

• Conveyors and material-handling equipment
• Agricultural machinery
• Packaging machines
• Food-processing equipment
• Textile machinery
• Fans and blowers
• Small pumps
• Woodworking machinery
• Light industrial production lines

Plummer Block Applications

SN- and SD-type plummer blocks are suitable for larger shafts, heavier radial loads, demanding operating conditions, and equipment that requires easier housing inspection and maintenance.

Here are the major applications in which they are used:

• Mining conveyors and crushers
• Steel mills and rolling mills
• Cement production equipment
• Paper-making machinery
• Large industrial fans
• Heavy-duty pumps
• Marine and port equipment
• Power-generation equipment
• Bulk material-handling systems
• Large industrial gearboxes

Part 6. Pillow Block vs Plummer Block: Key Differences

Based on the information above, you should now have a general understanding of the key differences between pillow blocks and plummer blocks. To make these differences clearer, the table below provides a direct comparison.

Part 7. Where to Buy Pillow Block or Plummer Block?

After reading this guide, you may have a better idea of which bearing housing or mounted bearing unit is suitable for your application.

If you need to purchase pillow blocks, plummer blocks, or complete bearing units but do not know where to buy them, BKZ Industry is a reliable option. Here are the reasons:

• Although BKZ Industry also manufactures other types of bearings, pillow block bearing units, plummer block housings, and other mounted bearing units are among its major products.
• BKZ Industry has more than 15 years of manufacturing and exporting experience in bearing housings and bearing units.
• BKZ Industry can offer factory-direct prices.
• BKZ Industry is ISO 9001 certified.
• BKZ Industry supports OEM services and factory visits.

Part 8. FAQS

Ending Note: Is a Pillow Block the Same as a Plummer Block?

Now, you can answer the question: Is a pillow block the same as a plummer block? The answer is no. A pillow block refers to a one-piece bearing housing, while a plummer block refers to an SN- or SD-type split bearing housing. They also use different types of bearings, so they are different in structure, bearing arrangement, load capacity, and application.

If you want to purchase pillow blocks or plummer blocks, you can contact BKZ Industry, a bearing manufacturer with more than 15 years of experience in bearing manufacturing and exporting.