HK3520 bearing: complete specifications & equivalents
The HK3520 is a ISO 3245 radial bearing sized 35 x 42 x 20 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 35 mm |
| Outer diameter D | 42 mm |
| Width B | 20 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 24.8 kN |
| Basic static load rating C0 | 47.5 kN |
| Fatigue load limit Pu | 5.8 kN |
| Limiting speed (mechanical) | 4700 rpm |
| Mass | 46 g |
| Manufacturer designation | HK3520 |
| 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 | 1.378 in |
|---|---|
| Outer diameter D | 1.654 in |
| Width B | 0.787 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 3.5 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) | 21 of 24 |
| Bore above smallest HK-series size | 32 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the HK3520 model number is decoded
As an open-end drawn-cup needle roller bearing in the HK-series (ISO 3245), NTN HK3520 is built around a thin hardened steel cup.Its printed envelope — 35 mm under-roller diameter, 42 mm outside diameter, 20 mm width — is fixed by ISO 3245; the 35 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. No suffix letters follow the size code: this is the basic caged drawn-cup execution in the HK range. In this class the limiting factor is rarely the rating table — a poorly supported or out-of-round seat will end the bearing long before fatigue does. Model and hobby drivetrains, from RC cars to small robotics, use this size because the thin cup lets designers shrink the gearbox around the gears rather than around the bearing. For low-temperature service, verify the grease is rated for the minimum ambient — a standard lithium grease in this cup will stiffen and starve the rollers on a cold start.
Typical equipment & failure modes
Common applications
- machine tool feed drive supports
- marine steering and linkage shafts
- rolling mill auxiliary drives
- continuous high-speed rotation where grease redistribution is the limiting factor
Known failure patterns
- cup cracking from an oval or tapered housing bore distorting the thin shell
- fretting of the cup outer surface in a soft or worn housing seat
- scoring of the needle rollers from abrasive contamination past the open ends
Selection pitfalls — read before you substitute
- Pressing HK3520 (35 mm shaft) home needs real force: keep the cup square with a guided mandrel, because a tilted cup overloads the roller row nearest the shoulder.
- With no suffix letters, HK3520 is the base caged execution: when replacing a branded equivalent, confirm the boundary dimensions 35×42×20 mm match exactly — suffix conventions for cage and shell variants differ between makers.
- The 20 mm wide section of HK3520 gains rating through longer rollers at 35 mm shaft; confirm the housing width accepts 20 mm — it will not drop into a seat machined for the 35×42 mm narrow variant.
- HK3520 runs directly on the shaft: the 35 mm shaft journal must be hardened to 58–64 HRC and ground to Ra ≤ 0.2 µm, or fit the matching IR inner ring instead.
- The open ends of HK3520 retain no lubricant: grease must be supplied by the housing arrangement, and adjacent seals are needed in dirty or washdown duty.
Frequently asked questions
What are the dimensions of a HK3520 needle roller bearing?
A HK3520 drawn-cup needle roller bearing has a 35 mm shaft diameter (Fw, under-roller diameter), 42 mm outside diameter and 20 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 HK3520 drawn-cup bearing?
Fw is the under-roller diameter — the diameter of the shaft journal on which the needle rollers run directly. For HK3520, Fw = 35 mm, so the shaft must be machined to 35 mm, hardened to 58–64 HRC and ground, unless a separate IR inner ring is fitted.
Can a HK3520 needle roller bearing carry axial load?
No. Drawn-cup needle roller bearings like HK3520 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 HK3520 retained in the housing?
The thin-walled drawn cup of HK3520 is press-fitted into a 42 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.
What duty conditions suit a HK3520 drawn-cup bearing?
HK3520 is typically specified for intermittent duty with long standstill periods that invite false brinelling; match the grease/oil speed limits (4700/7000 rpm) and radial load against the actual duty before finalizing.
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.