Fafnir3MM9105WIDULSuper Precision Angular Contact Ball Bearing 25x47x12 mm 25° ABEC 7/9 Duplex Universal Light Preload Matched Pair

Product Description

What this part is

A Fafnir 3MM9105WI-CR-DUL super-precision angular contact ball bearing in the 25 x 47 x 12 mm envelope, supplied as a matched duplex universal pair. The Fafnir 9100 series corresponds to the metric 70-series, so the 9105 size is the 7005 envelope, and the listing’s 7005-A cross reflects that same bore, outside diameter and width.

Decoding the designation

3MM — 25° contact angle in the Timken/Fafnir WI scheme
MM prefix — P4S precision, equivalent to ABEC 7/9
9105 — 25 mm bore, 7005 metric envelope
WI — super-precision spindle bearing series
CR — phenolic outer-land-riding cage
DU — duplex universal grinding, so the pair mounts back-to-back, face-to-face or in tandem
L — light preload

What these specs mean in practice

A 25° contact angle carries more thrust and less speed than a 15° bearing of the same envelope, which places this part in machine tool spindles where axial stiffness is the governing requirement. Light preload trades a little stiffness for lower running temperature and higher permissible speed than medium or heavy preload in the same size. The phenolic outer-land-riding cage is light, self-lubricating and tolerant of high cage speeds, and it sets a temperature ceiling below that of a machined bronze cage.

Published specifications

Bore: 25 mm (0.9843 in)
Outside diameter: 47 mm (1.8504 in)
Width per bearing: 12 mm (0.4724 in)
Total width of the pair: 24 mm (0.9449 in)
Contact angle: 25°
Precision class: P4S (ABEC 7/9)
Cage: phenolic, outer-land riding
Rows: single row per bearing
Closure: open

Quantity and configuration

2 Pcs, a duplex universal matched pair at light preload. Universal grinding means the two bearings produce the intended preload in any of the three standard arrangements when mounted together.

Fitting notes

The bearings mount with the marked faces adjacent for back-to-back or face-to-face arrangement, on a ground shaft seat and into a ground housing bore sized for the P4S class. Handling is done with the pair kept together, since the preload is created by the matched grinding of the two rings.

Interchange guidance

The direct equivalents are a 25°, P4 or P4S, duplex universal light-preload pair in the 7005 envelope from another super-precision maker — SKF 7005 CD/P4ADGA, FAG B7005-C-T-P4S-UL and NSK 7005A5TRDULP4 sit in that group. Same-envelope bearings with a 15° angle (7005 C, Fafnir 2MM9105WI) or a different preload grade (DUM, DUH) are related sizes rather than equivalents.