6309-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 6309-NSK model number is decoded

6309 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 09 by five gives the 45 mm bore; the 100 mm outside diameter and 25 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 45 mm shaft under normal load, catalogue practice seats it on a k5 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

• Sizes around 45 mm bore are normally pressed on cold with a sleeve against the inner-ring face; the press force must never route through the outer ring or the balls of 6309-NSK.
• The 63xx medium section at 45 mm bore gains dynamic rating through larger rolling elements on a 100 mm OD; the penalty is mass and a lower limiting speed than the 6209 — do not specify it for speed-critical shafts.
• Storage matters for open bearings: 6309-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 6309 units.
• Shaft and housing fillets must clear the bearing chamfer so the 25 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
• Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 6300-series position can soften the mixture and leak — clean out the old fill before switching grease types.
• The open 6309 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.
• The 45 mm bore puts 6309 in NSK's general-purpose industrial range; the standard pressed-steel cage and CN clearance cover most electric-motor and pump duty. NSK's VV non-contact seal is the high-speed choice here — DDU contact seal costs roughly 30–40% of the open-bearing speed ceiling.
• NSK rates 6309 at 58.5 kN dynamic (C) and 32 kN static (C0); this upper-medium rating covers conveyor and gearbox drives, but at these loads the pressed-steel cage can be the limiting factor under shock — consider the machined brass cage (suffix M) for impact duty.
• At 829 g, 6309 requires a soft-jaw vise or arbor press for mounting — never hammer it onto the shaft, and support the opposite ring to avoid brinelling the raceways.
• The 45×100×25 mm envelope of 6309 gives a D/d ratio of 2.22 and 27.5 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 58.5/32 kN load ratings, mass 829 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6309 on the 45×100×25 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6309 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.