6303-NSK bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NSK Rolling Bearings E1103 Part C) · extracted 2026-09-24

Cross references & equivalents

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 6303-NSK model number is decoded

6303 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the medium 63xx section (diameter series 3 of ISO 15), multiplying bore code 17 by five gives the 17 mm bore; the 47 mm outside diameter and 14 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 17 mm shaft under normal load, catalogue practice seats it on a j5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. In the NSK catalogue this open execution carries the bare designation; protected variants are ordered separately with suffixes ZZ (steel shields), VV (non-contact rubber seals) and DDU (contact rubber seals).

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Large bores like the 17 mm of 6303-NSK demand clean, burr-free seats; one raised burr under a ring this size cocks the bearing and concentrates load at the raceway edge, cutting life drastically.
• The 63xx medium series gains rating at 17 mm bore through a 47 mm OD and 14 mm width; the heavier rolling elements also trade away some speed versus a 6217.
• Storage matters for open bearings: 6303-NSK leaves the factory with rust preventive only, so clean it and apply the service grease at assembly even if the rings look oily from the wrapper.
• Open bearings tolerate the highest speeds in the 6300-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 6303 units.
• Assign fits by which ring rotates: an interference shaft fit for a rotating inner ring; if the outer ring rotates instead, reverse the logic — a loose rotating ring creeps and frets its seat.
• Deep-groove ball bearings tolerate only minutes of misalignment; if the 47 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6303-NSK.
• The open 6303 has no integral sealing; in the NSK E1103 catalogue the protected variants carry suffixes ZZ (non-contact steel shields), VV (non-contact rubber seals) and DDU (contact rubber seals). NSK does not offer a low-torque contact seal equivalent to NTN's LLH in this catalogue — for high-speed sealed duty specify the VV non-contact seal and an external housing labyrinth.
• At 17 mm bore the 6303 sits in NSK's small-bore range; NSK ships these sizes with a pressed-steel cage and P0 tolerance as standard, and NSK's EA (extra-precision) or P5 class is a special-order upgrade for spindle duty — do not assume catalogue P0 figures hold for instrument use without an NSK engineering check.
• At 15 kN dynamic load rating (C) and 6.65 kN static (C0), 6303 is a medium-load NSK bearing suitable for most electric-motor and pump duty; the C0/C0r ratio matters for preloaded or thrust-loaded arrangements, so confirm the static safety factor with the NSK catalogue.
• At 113 g, 6303 is light enough for hand assembly but should be pressed on with a fitting sleeve against the inner ring; do not strike the outer ring or cage with a hammer.
• The 17×47×14 mm envelope of 6303 gives a D/d ratio of 2.76 and 15.0 mm radial section height — a heavy NSK section built for high-load, lower-speed duty; specifying it in a high-rpm motor generates excess heat and shortens grease life, so prefer a 62/63-series there.
• The 15/6.65 kN load ratings, mass 113 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6303 on the 17×47×14 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6303 in a rated drive. NSK does not tabulate reference or limiting speeds in the E1103 Part C dimension tables used for this page — consult NSK's separate speed-rating tables before high-speed service.
• Keep NSK bearings in the original packaging until fitting: the wrapper carries the production lot, and the unopened shelf life of greased sealed units is typically quoted at three to five years in dry, vibration-free storage.
• Standard P0 runout from NSK is adequate up to the catalogue limiting speed on ground shaft seats; spindle or instrument positions should specify P6/P5 accuracy explicitly — it is a different order code, not a sorting of standard stock.