HK1812FM bearing: complete specifications & equivalents
The HK1812FM is a ISO 3245 radial bearing sized 18 x 24 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 | 18 mm |
| Outer diameter D | 24 mm |
| Width B | 12 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 8.3 kN |
| Basic static load rating C0 | 10.9 kN |
| Fatigue load limit Pu | 1.33 kN |
| Limiting speed (mechanical) | 8500 rpm |
| Mass | 13 g |
| Manufacturer designation | HK1812FM |
| 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 | 0.709 in |
|---|---|
| Outer diameter D | 0.945 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) | 15 of 24 |
| Bore above smallest HK-series size | 15 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the HK1812FM model number is decoded
As an open-end drawn-cup needle roller bearing in the HK-series (ISO 3245), NTN HK1812FM is built around a thin hardened steel cup.Its printed envelope — 18 mm under-roller diameter, 24 mm outside diameter, 12 mm width — is fixed by ISO 3245; the 18 mm figure is the shaft journal itself, which carries the rollers directly. 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. Mid-size drawn cups like this appear throughout passenger-car and light-truck transmissions, pressed into cast housings where a machined ring would not fit. Agricultural PTO shafts and small tractor linkages use this size at the pivot points: the cup is pressed into a welded eye and forgotten until the implement is overhauled. Mounting this size in a split housing needs the cup pressed into one half only, with the joint face relieved so the shell is not pinched when the case bolts come up to torque.
Typical equipment & failure modes
Common applications
- automotive manual transmission gear sets
- industrial gearbox lay shafts
- hydraulic pump and motor shafts
- shock-loaded start-stop service such as clutch and kick-starter mechanisms
Known failure patterns
- edge loading and needle skewing under shaft misalignment or deflection
- cage wear or fracture from sustained operation near the limiting speed
- cup cracking from an oval or tapered housing bore distorting the thin shell
Selection pitfalls — read before you substitute
- Press the drawn cup in with a mandrel bearing on the stamped face only — never hammer the cup or press through the rollers, that cracks or brinells the shell.
- Mid-size cups like HK1812FM (18 mm shaft) inherit the shape of their seat: a scored or oval housing bore from the previous bearing will cut the new bearing's life short.
- The cage in HK1812FM 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 18 mm.
- The 12 mm standard width of HK1812FM is the general-purpose section at 18 mm shaft; wider HK variants in the same 18×24 mm envelope carry more load and are not interchangeable if the housing width is fixed.
- Needle rollers tolerate almost no misalignment; if the 24 mm housing seat cannot be held square to the shaft, expect edge loading and early spalling.
Frequently asked questions
What duty conditions suit a HK1812FM drawn-cup bearing?
HK1812FM is typically specified for dirty environments where the open ends rely entirely on the housing seals; match the grease/oil speed limits (8500/13000 rpm) and radial load against the actual duty before finalizing.
What are the dimensions of a HK1812FM needle roller bearing?
A HK1812FM drawn-cup needle roller bearing has a 18 mm shaft diameter (Fw, under-roller diameter), 24 mm outside diameter and 12 mm width, per ISO 3245 boundary dimensions. It has no inner ring — the shaft journal serves as the raceway.
What does Fw mean on a HK1812FM drawn-cup bearing?
Fw is the under-roller diameter — the diameter of the shaft journal on which the needle rollers run directly. For HK1812FM, Fw = 18 mm, so the shaft must be machined to 18 mm, hardened to 58–64 HRC and ground, unless a separate IR inner ring is fitted.
Can a HK1812FM needle roller bearing carry axial load?
No. Drawn-cup needle roller bearings like HK1812FM 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 HK1812FM need a hardened shaft?
Either the 18 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 (IR15x18x12.5) so a standard unhardened shaft can be used.
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.