HK0408FT2 bearing: complete specifications & equivalents
The HK0408FT2 is a ISO 3245 radial bearing sized 4 x 8 x 8 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 4 mm |
| Outer diameter D | 8 mm |
| Width B | 8 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 1.77 kN |
| Basic static load rating C0 | 1.27 kN |
| Fatigue load limit Pu | 0.155 kN |
| Limiting speed (mechanical) | 30000 rpm |
| Mass | 2 g |
| Manufacturer designation | HK0408FT2 |
| 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 | 0.157 in |
|---|---|
| Outer diameter D | 0.315 in |
| Width B | 0.315 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 2 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) | 2 of 24 |
| Bore above smallest HK-series size | 1 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the HK0408FT2 model number is decoded
NTN HK0408FT2 belongs to the HK-series of open-end drawn-cup needle roller bearings (ISO 3245).Fw = 4 mm names the shaft journal that doubles as the inner raceway; around it the drawn cup measures 8 mm outside and 8 mm across. 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. At this miniature shaft size the cup wall is fractions of a millimetre thick, so handling cleanliness and housing-bore accuracy matter more than the paper load rating. Small compressor crankshafts and refrigeration equipment fit this size on the eccentric pin, where the housing bore is finish-bored in the same setup as the main bearing seats. Where the housing is a welded fabrication, finish-bore the seat after all welding and stress-relief is complete — pressing the cup into a distorted, as-welded bore guarantees early spalling.
Typical equipment & failure modes
Common applications
- small appliance gear drives
- instrument and meter linkages
- model and hobby drive trains
- 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
- At a 4 mm shaft diameter the cup wall of HK0408FT2 is extremely thin; inspect for transportation dents before pressing in, and deburr the housing bore edge or the cup will score and split on entry.
- The cage in HK0408FT2 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 4 mm.
- The 8 mm narrow section of HK0408FT2 is the compact option at 4 mm shaft: load capacity is limited by the short roller length, so verify the required rating before choosing it over a wider HK variant in the same 4×8 mm envelope.
- 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.
Frequently asked questions
What are the dimensions of a HK0408FT2 needle roller bearing?
A HK0408FT2 drawn-cup needle roller bearing has a 4 mm shaft diameter (Fw, under-roller diameter), 8 mm outside diameter and 8 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 HK0408FT2 drawn-cup bearing?
Fw is the under-roller diameter — the diameter of the shaft journal on which the needle rollers run directly. For HK0408FT2, Fw = 4 mm, so the shaft must be machined to 4 mm, hardened to 58–64 HRC and ground, unless a separate IR inner ring is fitted.
Can a HK0408FT2 needle roller bearing carry axial load?
No. Drawn-cup needle roller bearings like HK0408FT2 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.
How is a HK0408FT2 retained in the housing?
The thin-walled drawn cup of HK0408FT2 is press-fitted into a 8 mm housing bore (typically N6/N7 tolerance for steel housings). The press fit alone retains the cup — no snap rings or shoulders are needed, but the bore must be round and rigid.
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.