NACHI6224C3Single Row Deep Groove Ball Bearing 120x215x40 mm, Open, C3 Internal Clearance

Product Description

What this part is

A single-row deep groove ball bearing, 120 mm bore × 215 mm outside diameter × 40 mm width, open construction with no seals or shields, supplied with C3 internal clearance. Deep groove ball bearings carry heavy radial load with moderate axial load in either direction and will locate a shaft without a mating bearing. At a 120 mm bore this is a substantial industrial bearing — roughly 5 kg — and the pieces around it in a drive train are sized to match.

Decoding the designation

6224 – ISO base number for the single-row deep groove ball bearing with the 120 × 215 × 40 mm envelope. The 6200 series is the light-to-medium section; the 22 is the bore code (22 × 5 = 110… note that bore codes above 20 run 04 = 20 mm upward, giving 24 = 120 mm).
C3 – radial internal clearance greater than normal, per the ISO clearance classes (C2, normal/CN, C3, C4, C5).
JEM – a NACHI series and market code that appears on this line. It is retained above as a search term; it does not change the bearing envelope.

Why C3 clearance matters, and why mismatching it fails both ways:
Internal clearance is the small amount of free radial play inside an unmounted bearing. Almost all of it disappears once the bearing is installed and running. An interference fit on the shaft expands the inner ring and eats clearance. Heat does the same thing: the inner ring usually runs hotter than the outer ring, so it grows more, and the difference closes the gap further.

C3 exists so that after those losses there is still working clearance left. Specify it for a tight press fit on the shaft, for a hot-running machine, or where there is a temperature gradient across the bearing — motors, pumps handling hot fluid, gearboxes near a heat source.

Get the clearance class wrong and it bites in both directions. A C3 bearing fitted where normal clearance was intended keeps too much internal play once it is running: the load zone is narrower than designed, so fewer balls share the load, the bearing runs noisy, and the raceway sees higher contact stress than the calculation assumed. Go the other way and a normal-clearance bearing on a hot or tightly fitted shaft loses all of its clearance, goes into internal preload, generates its own heat, and seizes. Neither substitution is safe — match the class the machine was designed around.

Published ratings and mounting data

Figures below are for the 6224 envelope and are drawn from distributor catalogue data rather than a NACHI publication, so treat them as provisional pending confirmation against NACHI’s own catalogue.

Basic dynamic load rating (C): approximately 145 kN
Basic static load rating (C0): approximately 117 kN
Limiting speed, grease: approximately 6 200 r/min
Limiting speed, oil: approximately 3 900 r/min – note this figure is reported below the grease figure in the source data, which is the reverse of the usual relationship and is flagged here as suspect
Approximate mass: 5.2 kg

The static rating sitting below the dynamic rating is normal for a deep groove ball bearing; the two ratings measure different failure modes and are not directly comparable.

Quantity and configuration

One bearing. A single deep groove bearing, not a set, no seals, shields or snap ring.

Fitting notes

At a 120 mm bore, heat mounting is strongly preferred over pressing. Warm the inner ring evenly to roughly 80 to 110 °C on an induction heater and slide it onto the shaft; never apply a flame directly and never drive mounting force through the ball complement. Whichever ring takes the interference fit is the ring you press against. Open bearings are supplied with a preservative coating rather than a service lubricant, so grease to the machine builder’s specification before running.

Interchange guidance

The 6224 base number is common to all major manufacturers, so SKF 6224/C3, FAG 6224.C3, NSK 6224C3, NTN 6224C3, Koyo 6224C3 and Timken 6224 C3 all share the 120 × 215 × 40 mm envelope. Confirm the clearance suffix on any substitute — a plain 6224 without the C3 marking is a different bearing for the purposes described above, even though it drops into the same seat.