6305-ZZ-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 6305-ZZ-NSK model number is decoded

In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6305 carries bore code 05 = 25 mm. Outside diameter 62 mm and width 17 mm come from the ISO 15 boundary-dimensions general plan. Suffix -ZZ denotes two non-contact metallic shields; they retain grease and block coarse debris but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 25 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. NSK catalogue order number: 6305ZZ (suffix ZZ), two non-contact steel shields, mapped here from the industry-neutral -ZZ spelling.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• At a 25 mm bore, a shaft-seat burr or an overtight setscrew can score the thin inner ring of 6305-ZZ-NSK; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
• The 63xx medium section at 25 mm bore gains dynamic rating through larger rolling elements on a 62 mm OD; the penalty is mass and a lower limiting speed than the 6205 — do not specify it for speed-critical shafts.
• Do not wash 6305-ZZ-NSK in solvent before mounting: the grease inside the shielded cavity is the service fill, and solvent creeping past the shield gap strips it out.
• Shielded 6305-ZZ-NSK units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
• Measure the shaft, do not trust the drawing: a 25 mm nominal journal worn by even 0.02 mm turns an interference seat into a creeping fit that frets the bore of 6305-ZZ-NSK.
• 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.
• NSK catalogues the shielded version as 6305ZZ — suffix ZZ, two non-contact steel shields. The industry-neutral page spelling is -ZZ; quote the NSK order number when buying through an NSK channel.
• The 25 mm bore puts 6305 in NSK's light industrial range; the standard pressed-steel cage and CN clearance cover most fractional-horsepower motor and small-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.
• At 22.6 kN dynamic load rating (C) and 11.2 kN static (C0), 6305 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 235 g, 6305 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 25×62×17 mm envelope of 6305 gives a D/d ratio of 2.48 and 18.5 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 22.6/11.2 kN load ratings, mass 235 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6305ZZ on the 25×62×17 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6305 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.
• 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.
• NSK supplies its sealed units pre-greased for general duty between roughly -10 and +110 °C; low-temperature, food-grade and high-temperature fills are special executions — ask at order time, because DDU/VV units are not designed to be opened and repacked.