HK0408 bearing: complete specifications & equivalents
The HK0408 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 | SKF |
| Bore diameter d | 4 mm |
| Outer diameter D | 8 mm |
| Width B | 8 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 1.76 kN |
| Basic static load rating C0 | 1.37 kN |
| Fatigue load limit Pu | 0.14 kN |
| Reference speed (thermal) | 22000 rpm |
| Limiting speed (mechanical) | 26000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2 g |
| Manufacturer designation | HK 0408 |
| Standard | ISO 3245 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.2 drawn cup needle roller bearings |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.2 drawn cup needle roller bearings) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.2 drawn cup needle roller bearings); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.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 | 08 |
| Radial section height (D−d)/2 | 2 mm |
| Smallest bore in HK-series | 3 mm |
| Largest outer diameter in HK-series | 68 mm |
| Width range across HK-series | 6–38 mm |
| Bore position in HK-series (smallest first) | 2 of 26 |
| Bore above smallest HK-series size | 1 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| HK0408FT2 | NTN | full Dimensions and internal design equivalent — standard interchange. | NTN counterpart on the same 4×8×8 mm envelope with ratings within 10 % — interchange after checking the execution (cage/seal) details on both pages. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the HK0408 model number is decoded
The drawn cup bearing HK 0408 gives the smallest radial section of any caged needle bearing with its own outer ring: 4 mm Fw, 8 mm OD and 8 mm width, the shell pressed directly into the housing bore. Reading the code: HK marks the open-end drawn cup series, the first two digits (04) give the 4 mm under-roller diameter Fw, the last two (08) the 8 mm width; the 8 mm OD follows the ISO 3245 plan. Open caged execution: the standard HK drawn cup with steel cage, relubricable through the shaft where the housing allows. The suffix TN denotes the glass fibre reinforced PA66 cage; the 2RS execution adds rubber contact seals on both faces, retaining factory grease for life-lubricated pivots. The 2 g catalogue mass and 2.0 mm radial section ((8−4)/2) frame a rating of about 0.44 kN dynamic per millimetre of bore — the needle construction's density advantage over ball bearings of the same envelope. Open ends mean the housing must do the sealing; where that is impossible, the 2RS execution with its integrated seals and grease fill replaces sealing rings that would not fit the 8 mm section.
Typical equipment & failure modes
Common applications
- spindle clusters of drilling and tapping units
- auto steering gear rack supports
- clutch release mechanisms and cable pulleys
- office equipment and power tool gear trains
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- fretting corrosion of the cup outside diameter in a soft or oversized housing bore
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- hard-particle indentation in unfiltered lubricant
Selection pitfalls — read before you substitute
- At Fw 4 mm the rolling elements are under two millimetres long — handle the HK 0408 like a watch part: one dropped assembly, one over-pressed cup or one coarse journal finish outweighs any catalogue rating difference.
- Contamination, not fatigue, kills most small needle bearings: with raceways this narrow, one hard particle dents a full-width line — seal the housing even when the bearing execution itself is open.
- Do not interchange envelope-identical needle families blindly: HK 0408 shares its 4×8×8 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- The 1.76/1.37 kN ratings and 2 g mass are SKF catalogue values transcribed from ch. 7.2 of PUB BU/P1 17000 (PDF table page 620); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What mounting mistakes ruin a HK 0408?
Press the cup in with a shouldered mandrel bearing on the stamped face, into a housing bore sized for a firm press fit; never hammer it or press through the rollers. Then slide the hardened shaft in. For 2RS executions the seals and grease are already in place — no additional sealing is needed.
Is the HK 0408 sealed?
No — the open-end HK cup has no seals: the housing must keep contamination out and grease in. The 2RS execution of the same code adds both-side contact seals with a grease fill.
Which dimensions does the HK 0408 have?
A HK 0408 measures 4 mm bore/Fw × 8 mm outside diameter × 8 mm width (0.157 × 0.315 × 0.315 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 1.76 kN, static C0 1.37 kN, fatigue limit Pu 0.14 kN, limiting speed 26,000 r/min, reference speed 22,000 r/min, mass about 2 g.
What does HK 0408 mean in SKF part numbering?
HK = open-end drawn cup needle roller bearing (ISO 3245); the first two digits give Fw 4 mm, the last two the width 8 mm, the shell OD 8 mm follows the plan. 2RS adds both-side contact seals, TN the polymer cage.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.2 drawn cup needle roller bearings on 2026-09-26. Read our editorial & correction policy.