KOYO HK 1812 18x24x12 - Drawn Cup Needle Roller Bearing

KOYO HK 1812 18x24x12 - Drawn Cup Needle Roller Bearing

KOYO HK 1812 is a drawn cup needle roller bearing with cage with dimensions 18x24x12 mm. Its thin-walled outer ring and needle roller construction provide substantial radial load capacity within a very small installation space. The standard HK1812 design is open at both ends and supplied without a separate inner ring, allowing a suitably hardened and finished shaft to function directly as the inner raceway.

Technical Specifications - KOYO HK 1812

Manufacturer: KOYO / JTEKT
Designation: HK1812 / HK 1812
Product type: Needle roller bearing
Series: HK
Design: Drawn cup needle roller bearing
Raceway diameter Fw: 18 mm
Outside diameter D: 24 mm
Width C: 12 mm
Dimensions: 18x24x12 mm
Rolling elements: Needle rollers
Cage: Yes
Inner ring: Not included
Ends: Open
Outer ring: Thin-walled drawn cup
Primary load direction: Radial
Installation: Press fit into a suitable housing bore

Dimensions 18x24x12 mm

The principal identification dimensions are:

Fw: 18 mm
D: 24 mm
C: 12 mm

The difference between the 18 mm needle roller raceway diameter and the 24 mm outside diameter is only 6 mm. This illustrates the compact radial cross-section provided by the drawn cup needle roller design.

Drawn Cup Construction

A defining feature of KOYO HK1812 is its thin-walled, drawn outer cup.

Unlike bearings with conventional machined outer rings, the drawn cup requires very little radial installation space. Once correctly press-fitted into the housing bore, the housing supports the thin outer ring and helps establish the required bearing geometry.

This construction is particularly useful when the available space between the shaft and housing is limited.

Caged Needle Roller Design

HK1812 uses needle rollers guided by a cage.

The cage maintains correct spacing between the needle rollers and reduces direct contact between adjacent rolling elements. This construction provides an effective combination of compact dimensions, radial load capacity and operating speed capability.

The use of a cage also distinguishes HK-series bearings from full-complement needle roller designs.

Bearing Without an Inner Ring

Standard KOYO HK 1812 does not incorporate a separate inner ring.

Instead, the shaft can function directly as the inner raceway. For this arrangement, the shaft surface in contact with the needle rollers must provide appropriate:

• hardness
• dimensional accuracy
• roundness
• surface finish
• raceway quality

Using the shaft directly as the raceway reduces the radial space required by the complete bearing arrangement.

Radial Load Capability

The long, small-diameter needle rollers provide a large effective contact area relative to the bearing's radial dimensions.

For this reason, HK1812 is primarily designed to accommodate radial loads.

The bearing itself is not intended to provide significant axial location. Where axial forces occur, the machine design should incorporate an appropriate separate thrust-bearing or axial-guidance arrangement.

Open-Ended Design

The standard HK1812 is open at both ends, allowing the shaft to pass completely through the bearing.

This should be distinguished from closed-end drawn cup needle roller bearings, which are designed for shaft ends that terminate inside the bearing position.

Checking the open or closed configuration is therefore important when selecting a replacement.

Why Use an HK1812 Bearing?

The combination of a 18 mm raceway diameter, 24 mm outside diameter and 12 mm width allows the bearing to provide radial support where installation space is severely restricted.

Key operational advantages include:

• compact radial cross-section
• needle roller contact geometry
• efficient radial load support
• open-ended construction
• caged rolling elements
• possibility of using the shaft directly as the inner raceway

Typical Applications

KOYO HK1812 can be used in appropriately designed:

• industrial gearboxes
• drive mechanisms
• power tools
• automation equipment
• agricultural machinery
• compact shaft assemblies
• transmission mechanisms
• industrial machinery

Final selection should consider load, rotational speed, lubrication, shaft hardness, housing accuracy and operating temperature.

Replacement Identification - KOYO HK1812

When identifying a replacement, verify:

Brand: KOYO / JTEKT
Designation: HK1812
Bearing type: Needle roller bearing
Construction: Drawn cup
Dimensions: 18x24x12 mm
Cage: Yes
Inner ring: Not included
Ends: Open
Primary loading: Radial

Matching dimensions alone should not be treated as complete confirmation of interchangeability. The bearing design, open-ended configuration and requirements for the shaft raceway should also correspond to the original application.

FAQ - KOYO HK 1812

What are the dimensions of KOYO HK 1812?
The bearing dimensions are 18x24x12 mm, with an 18 mm needle roller raceway diameter, 24 mm outside diameter and 12 mm width.

What type of bearing is HK1812?
It is a drawn cup needle roller bearing with a cage.

Does KOYO HK1812 have an inner ring?
No. The standard HK1812 is supplied without a separate inner ring.

Can the shaft act as the inner raceway?
Yes. A suitably hardened, accurately machined and correctly finished shaft surface can function directly as the inner raceway.

Does HK1812 have a cage?
Yes. The needle rollers are separated and guided by a cage.

Is KOYO HK 1812 open at both ends?
Yes. Standard HK1812 is an open-ended needle roller bearing.

What loads does HK1812 primarily support?
It is designed primarily to accommodate radial loads.

Why is HK1812 suitable for compact mechanisms?
Its thin drawn outer cup and needle roller construction provide radial load capacity with only a small difference between the 18 mm raceway diameter and 24 mm outside diameter.