3309-DNRCBM bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27

Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); 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.

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 3309-DNRCBM model number is decoded

3309 DNRCBM is SKF's 45 mm-bore double-row angular-contact ball bearing of the 3300 series — two ball rows back-to-back for two-direction axial location in one unit, 45×100×39.7 mm. A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. D marks a two-piece (split) inner ring that simplifies mounting of the heavy 33-series section. NR adds a snap-ring groove in the outer ring supplied with the appropriate snap ring, and CB gives controlled axial clearance. DNRCBM combines the split inner ring, snap ring (NR), controlled CB clearance and a machined brass ball-centred M cage. CB means universally matchable with Normal axial internal clearance: the two side faces are ground so any two units form DB (back-to-back), DF (face-to-face) or DT (tandem) sets without regrinding. Envelope 45×100×39.7 mm (1.772×3.937×1.563 in), 27.5 mm radial section height, C 61.8 kN, C0 52 kN, Pu 2.2 kN.reference speed 7,500 r/min (thermal) and limiting speed 6,300 r/min (mechanical), catalogue mass 1500 g. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 6,300 r/min while thermal balance under catalogue load sets the 7,500 r/min reference; at dm ≈ 72.5 mm the corresponding dn is approximately 457k mm·r/min. At the printed limiting speed of 6,300 r/min the mean pitch diameter dm ≈ 72.5 mm implies a dn value around 457k mm·r/min; the 7,500 r/min reference speed is the thermal-planning figure under catalogue load. Speed-ratio note for this exact unit: the reference speed is 7,500 r/min against a 6,300 r/min limiting speed, i.e. a reference-to-limit ratio of 1.19.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• The double-row 3309 takes thrust in both directions by itself — that is the reason to choose it over two single-row bearings: one housing bore, one fit, built-in set geometry.
• Interference goes on the rotating ring (about k5 at 45 mm bore); the wide 39.7 mm ring is sensitive to tilted seats, so check squareness before clamping.
• Compared with a single-row pair of the same bore, the double-row 3309 occupies less axial space but offers less freedom to adjust preload — do not substitute without re-checking the arrangement.
• Controlled axial clearance is the heart of the design: CB denotes controlled Normal axial clearance between the two rows; check residual clearance after mounting and at operating temperature.
• The D executions have a two-piece inner ring: mount both halves square to each other, never press on the outer ring, and keep the split faces clean during fitting.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for 3309 DNRCBM as the double d nr cb m execution; the other order numbers of the 3309 size are different products and may carry different ratings — always quote the full designation when purchasing.