6308-ZZ-NTN bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)) · extracted 2026-09-25

Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings 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.

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 6308-ZZ-NTN model number is decoded

In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6308 carries bore code 08 = 40 mm. Outside diameter 90 mm and width 23 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 40 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. NTN catalogue order number: 6308ZZ (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

• A 40 mm shaft for 6308 should be finished to Ra ≤ 1.6 µm with square seating faces; at this bore a scored or oval journal shows up directly as running noise and early raceway damage.
• The 63xx medium section at 40 mm bore gains dynamic rating through larger rolling elements on a 90 mm OD; the penalty is mass and a lower limiting speed than the 6208 — do not specify it for speed-critical shafts.
• Do not wash 6308-ZZ-NTN 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 6308-ZZ-NTN units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
• Vibration during standstill brinells the raceways of a 40 mm bearing at ball spacing; if the machine sits idle next to running equipment, turn the shaft over periodically or isolate the arrangement.
• Axial location must clamp the ring face, not the seal area: a shoulder or circlip bearing on the seal side of the 23 mm-wide ring of 6308-ZZ-NTN drags the lip and overheats it.
• NTN catalogues the shielded version as 6308ZZ — suffix ZZ, two non-contact steel shields. The industry-neutral page spelling is -ZZ; quote the NTN order number when buying through an NTN channel.
• The 40 mm bore puts 6308 in NTN's general-purpose industrial range; the standard pressed-steel cage and CN clearance cover most electric-motor and pump duty, but for continuous high-speed use specify the LLH low-torque seal (not LLU) and confirm the housing allows the listed limiting speed.
• At 6400 r/min the grease limiting speed for 6308 covers medium-duty industrial drives; the open or shielded execution can run continuously at this speed with standard lithium-soap grease.
• NTN rates 6308 at 45 kN dynamic (C) and 24 kN static (C0), 1.83 kN fatigue load limit Cu; 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 630 g, 6308 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 40×90×23 mm envelope of 6308 gives a D/d ratio of 2.25 and 25.0 mm radial section height — a heavy 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 45/24 kN load ratings, 1.83 kN fatigue load limit Cu NTN lists the grease limiting speed at 6400 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 630 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6308ZZ on the 40×90×23 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6308 in a rated drive.
• Standard catalogue stock of 6308 is the general-purpose execution; for low-noise motor duty NTN offers low-torque seal and special-grease variants in this size class, which are separate order numbers.
• NTN's pressed-steel cage (no cage suffix) is the quiet standard for this size; for sustained running close to the limiting speed or for heavy shock duty, ask the NTN channel whether a machined-cage execution of 6308 is listed.