Fafnir2MM9105WISuper-Precision Angular Contact Ball Bearing 25 x 47 x 12 mm, 15 Degree Contact Angle, P4S, Phenolic Cage, Open, 1 Pc

Product Description

What this part is

A single Fafnir (now Timken) super-precision angular contact ball bearing in the 7005 envelope — 25 mm bore, 47 mm outside diameter, 12 mm width. Open, no seals or shields, with a 15° contact angle and P4S tolerances, built for machine-tool spindles, grinding heads and other high-speed precision rotary work.

Decoding the designation

2MM — Fafnir super-precision angular contact series, 15° 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, as carried on the box legend for this series.
No SU, DU or preload letter follows, so this is a single bearing supplied without a specified matched-set preload.

What these specs mean in practice

The 15° contact angle is the high-speed end of the super-precision range. A shallower angle puts the ball load closer to radial, which cuts centrifugal ball loading and heat generation at speed — so a 15° bearing spins faster and runs cooler than the 25° build in the same envelope, but carries appreciably less thrust and gives less axial stiffness. That is the trade: choose 15° for spindle speed, 25° when the cut pushes hard along the axis. P4S is the tighter of the two common super-precision grades, holding bore, outside diameter and running accuracy to ABEC 7/9 limits. The phenolic cage is light and self-lubricating, which is what allows the high speed, but it will not tolerate aggressive solvents or sustained high temperature.

Quantity and configuration

1 Pc — one bearing. This is not a matched pair. If your spindle uses a preloaded set, order two like bearings that carry the same universal-grinding code, or specify a DU set instead.

Fitting notes

Angular contact bearings take thrust in one direction only, so the assembly must oppose it — another bearing, a spring pack or a shoulder. A P4S bearing only delivers P4S runout if the shaft and housing seats are ground and burr-free to match; sloppy seats waste the tolerance class entirely. Keep the bearing in its packaging until the moment it goes on, use a spindle-grade grease sparingly or run oil-air, and do not press through the balls.

Interchange guidance

Fafnir super-precision now trades under the Timken name; the number is unchanged. Genuine 15° cross-references in this size include SKF 7005 CD/P4A, FAG B7005-C-T-P4S, NSK 7005C and RHP 7005CT. Related sizes share the identical 25 x 47 x 12 mm envelope but change the contact angle — 3MM9105WI is the 25° build. That is a different part with different thrust capacity and speed rating, not a substitute, though it is worth knowing it exists if 25° is what your spindle actually calls for.