HK2012FM bearing: complete specifications & equivalents
The HK2012FM is a ISO 3245 radial bearing sized 20 x 26 x 12 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 20 mm |
| Outer diameter D | 26 mm |
| Width B | 12 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 8.75 kN |
| Basic static load rating C0 | 12.1 kN |
| Fatigue load limit Pu | 1.48 kN |
| Limiting speed (mechanical) | 8000 rpm |
| Mass | 14 g |
| Manufacturer designation | HK2012FM |
| Standard | ISO 3245 |
| Catalog version | CAT. No. 2203-3/E 2024 |
| Last verified | 2026-09-25 |
Source: catalog reference (CAT. No. 2203-3/E 2024) · extracted 2026-09-25
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (CAT. No. 2203-3/E 2024); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & HK-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.024 in |
| Width B | 0.472 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 3 mm |
| Smallest bore in HK-series | 3 mm |
| Largest outer diameter in HK-series | 58 mm |
| Width range across HK-series | 6–38 mm |
| Bore position in HK-series (smallest first) | 16 of 24 |
| Bore above smallest HK-series size | 17 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the HK2012FM model number is decoded
In the HK-series (ISO 3245), HK2012FM is NTN's open-end drawn-cup needle roller bearing.Boundary dimensions are 20 mm under-roller diameter (Fw — the shaft journal acts as the raceway), 26 mm cup outside diameter and 12 mm width. There is no separate inner ring — the thin-walled cup is drawn from sheet steel, hardened, and press-fitted into the housing, giving the smallest radial section of any rolling bearing at this shaft size. The FM/FT2 suffix marks NTN's caged drawn-cup execution: a formed steel cage keeps the rollers evenly spaced, lowering friction and noise versus full-complement drawn cups. In this mid size range the HK cup is the standard compact radial bearing choice across automotive and industrial gearboxes. This size is frequently specified in motorcycle gear-selector mechanisms, where the shaft is short, the housing is cast around the bearing, and the roller set must survive repeated shock from shift forks. Grease for this size should be a soft NLGI 1 or 2 lithium-complex grade: the open cup lets the housing supply the lubricant, and a stiff grease will not flow back through the roller set after standstill.
Typical equipment & failure modes
Common applications
- universal joint and steering pivots
- automotive manual transmission gear sets
- industrial gearbox lay shafts
- reciprocating or oscillating motion where the rollers never complete a full revolution
Known failure patterns
- raceway spalling on a shaft that was below the required 58–64 HRC hardness
- edge loading and needle skewing under shaft misalignment or deflection
- cage wear or fracture from sustained operation near the limiting speed
Selection pitfalls — read before you substitute
- The cage in HK2012FM spaces the rollers but is not a seal: it retains nothing against dust or washdown, so the housing still needs its own sealing arrangement at 20 mm.
- The 12 mm standard width of HK2012FM is the general-purpose section at 20 mm shaft; wider HK variants in the same 20×26 mm envelope carry more load and are not interchangeable if the housing width is fixed.
- The open ends of HK2012FM retain no lubricant: grease must be supplied by the housing arrangement, and adjacent seals are needed in dirty or washdown duty.
- At a 20 mm shaft diameter, check housing bore roundness after previous bearing removal for HK2012FM; a pulled or scored seat must be re-machined or sleeved before the new cup goes in.
Frequently asked questions
What does Fw mean on a HK2012FM drawn-cup bearing?
Fw is the under-roller diameter — the diameter of the shaft journal on which the needle rollers run directly. For HK2012FM, Fw = 20 mm, so the shaft must be machined to 20 mm, hardened to 58–64 HRC and ground, unless a separate IR inner ring is fitted.
Can a HK2012FM needle roller bearing carry axial load?
No. Drawn-cup needle roller bearings like HK2012FM carry radial load only and provide no axial shaft location. Axial forces must be carried by separate thrust washers or a locating bearing in the arrangement.
Does HK2012FM need a hardened shaft?
Either the 20 mm shaft journal must be hardened to 58–64 HRC and ground to Ra ≤ 0.2 µm, or you can fit the matching inner ring (IR15x20x13) so a standard unhardened shaft can be used.
What are the dimensions of a HK2012FM needle roller bearing?
A HK2012FM drawn-cup needle roller bearing has a 20 mm shaft diameter (Fw, under-roller diameter), 26 mm outside diameter and 12 mm width, per ISO 3245 boundary dimensions. It has no inner ring — the shaft journal serves as the raceway.
Reviewed & verified by the MPN Base engineering desk against source catalog CAT. No. 2203-3/E 2024 on 2026-09-25. Read our editorial & correction policy.