Fafnir3MM9105WIDULSuper-Precision Angular Contact Ball Bearing 25 x 47 x 12 mm, 25 Degree Contact Angle, P4S, Phenolic Cage, Universally Ground Duplex Pair, Light Preload, 2 Pcs

Product Description

What this part is

A matched duplex pair of Fafnir (now Timken) super-precision angular contact ball bearings in the 7005 envelope — 25 mm bore, 47 mm outside diameter, 12 mm width per bearing. Two pieces ship together as one universally ground set, ready to mount as a preloaded unit in machine-tool spindles, grinding heads and high-speed rotary assemblies.

Decoding the designation

3MM — Fafnir super-precision angular contact series, 25° contact angle; the MM prefix carries P4S tolerances (ABEC 7/9).
9105 — the 7005 size, 25 x 47 x 12 mm.
WI — Fafnir super-precision angular contact design code.
CR — phenolic outer-land-riding cage.
DU — duplex, universally ground.
L — light preload.

What these specs mean in practice

A 25° contact angle sits in the middle of the super-precision range: it carries substantially more thrust than a 15° bearing, and gives up some of that bearing’s top speed. Light preload is the low-heat choice — it holds running temperature and power draw down at speed, at the cost of axial rigidity against medium or heavy preload. Universal grinding means the rings are ground so that simply clamping the pair together produces the specified preload; there are no shims to calculate. The phenolic cage is light, quiet and self-lubricating, which is why it is standard on spindle bearings, but it dislikes aggressive solvents and sustained high temperature.

Quantity and configuration

2 Pcs — one universally ground duplex pair, both bearings shipping together as a set.

Fitting notes

Keep the pair together; substituting a bearing from another set throws away the ground preload. Mount back-to-back for maximum moment stiffness, or face-to-face where shaft and housing alignment is less certain. Seating surfaces matter more here than on a standard bearing — a P4S bearing only delivers P4S runout if the shaft and housing bores are ground to match, clean and burr-free. Lubricate sparingly with a spindle grease or run oil-air.

Interchange guidance

Fafnir super-precision is sold under the Timken name today and the number is unchanged. Genuine 25° cross-references in this envelope include SKF 7005 ACD/P4A, FAG B7005-E-T-P4S, NSK 7005A5 and RHP 7005E in matched light-preload pairs. Related sizes share the same 25 x 47 x 12 mm envelope with a different contact angle — 2MM9105WI is the 15° build and is a different part, not a substitute. Preload grade is likewise not interchangeable: DUM (medium) and DUH (heavy) are also available in this size.