FafnirSuper Precision Angular Contact Ball Bearing 120 x 215 x 40 mm, 25° Contact Angle, P4S / ABEC 7 Class, Heavy 72xx Section, Single Universal Light Preload

Product Description

What this part is

A super precision angular contact ball bearing in the 7224 envelope — 120 mm bore, 215 mm outside diameter, 40 mm width. This is Fafnir’s spindle bearing range in a heavy section: single row, open, universally ground, and held to the tolerance grade machine tool builders specify for main spindle and precision rotary positions.

Decoding the designation

3MM: Fafnir super precision series with a 25° contact angle. The MM prefix carries P4S tolerance, ABEC 7 running accuracy with tighter ABEC 9 bore and outside diameter control. 224: the Fafnir 2xx block maps to the ISO 72xx dimension series, so this is the 7224 envelope, 120 x 215 x 40 mm. WI: Fafnir super precision angular contact spindle bearing. SUL: single, universally ground, light preload.

What these specs mean in practice

The 7224 is a deliberately heavy section for a 120 mm shaft. Set against the 7024 in the same bore it runs 215 mm outside diameter against 180, and 40 mm wide against 28. That extra section goes into a larger ball complement and thicker rings, which buys load capacity and stiffness at the cost of mass and limiting speed. A 72xx section suits a spindle or table holding position under heavy cutting or heavy overhung load.

A 25° contact angle sits in the middle of the spindle range. Against a 15° bearing it takes substantially more thrust and gives a stiffer axial response; against a 30° or 40° bearing it runs faster and generates less heat. Light preload then pulls back the other way — minimum internal friction, minimum heat generation, the highest permissible speed of the three preload classes, at the cost of some stiffness. A heavy section at light preload is a coherent combination: the capacity comes from the geometry rather than from clamping the bearing up tight.

Quantity and configuration

The SUL suffix denotes a single universally ground bearing, and one bearing is what ships. Universal grinding is what makes a single useful: two or more of these clamp together into a back-to-back (DB) set for maximum moment stiffness and two-direction thrust, a face-to-face (DF) set where housing alignment is imperfect, or a tandem (DT) set to double one-direction thrust — each developing the specified light preload with no shims and no spacer stack to calculate.

Interchange guidance

Fafnir super precision is now supplied under the Timken brand and the Fafnir numbers remain in active cross-reference use. Same-envelope 25° equivalents include RHP 7224-E-T-SUL-P4, where RHP E is 25°, and SKF 7224 ACD/P4A, where SKF AC is 25°. Both are true contact angle matches. Also NSK 7224A5, FAG B7224-E-T-P4S and NTN 7224 in the corresponding precision grade. The 7224A reference also carried on this listing shares the 120 x 215 x 40 mm envelope; a plain A suffix in NSK nomenclature indicates 30°, so it is kept as a dimensional cross-reference rather than a contact angle claim. The 15° sibling is 2MM224WI, a different bearing and not a substitute inside an existing set. The -3 element in the source designation is an order or customer specific suffix, carried here as a searchable reference rather than published as a specification.