Fafnir2MM9516WISuper Precision Spindle Angular Contact Ball Bearing 80 mm Bore, 15 Degree Contact Angle, ISO P4S – Outside Diameter and Width To Be Confirmed

Product Description

What this part is

A Fafnir super-precision spindle angular contact ball bearing with an 80 mm bore, 15° contact angle, from the MM-prefix machine tool range. Fafnir is now part of Timken.

Correcting the source data

This listing needs an honest caveat rather than a confident specification, so here it is. The designation as marked reads 2MM9516WI, and Timken publishes no 95xx WI series. The WI spindle series Timken does publish are 9300 (the 719xx envelope), 9100 (the 70xx envelope), 99100, 200 (72xx) and 300 (73xx). Searching Timken’s own catalogue for 2MM9516WI returns nothing.

What is solid: the bore code 16 corresponds to 80 mm, which is consistent across every WI series, and the 2MM prefix confirms 15° and ISO P4S. What is not solid is the series digit and therefore the outside diameter and width. The two candidate readings are:

2MM9116WI — the 9100 series, ISO equivalent 7016C, envelope 80 × 125 × 22 mm. This matches the 125 mm outside diameter carried in the original listing.
2MM9316WI — the 9300 series, ISO equivalent 71916C, envelope 80 × 110 × 16 mm.

The original listing gave 80 × 125 × 24 mm. The 24 mm width matches no bearing in either candidate series, so it has been withdrawn rather than republished — a width nobody makes is worse than no width at all. The 125 mm outside diameter is retained as reported because it corroborates the 9100 reading, but it is reported, not verified.

Before ordering, ask for a measurement of the outside diameter and width, or a photograph of the ring etching. If it measures 80 × 125 × 22 it is a 2MM9116WI and cross-references to 7016C. If it measures 80 × 110 × 16 it is a 2MM9316WI and cross-references to 71916C. Those are different bearings with different ratings and they are not interchangeable.

What the confirmed part of the designation means

2MM — super-precision spindle bearing at the low contact angle, 15°. Timken’s catalogue states that 2 is the Timken designation and C the ISO designation for 15°.
16 — bore code, 80 mm.
WI — angular contact geometry, full shoulders both sides of the inner ring and a low shoulder on the outer, thrust one direction, non-separable.
MM prefix precision — ISO P4S: running accuracy and performance to ABEC 9 (ISO P2) levels, other features to ABEC 7 (ISO P4). The original listing described this as ABEC 7, which understates the running accuracy by one class.

What a 15° angle means in practice

15° biases the bearing toward radial load and speed. It runs cooler than a 25° bearing at equal rpm, holds radial running accuracy better and reaches a higher limiting speed — which is why grinding spindles and high-speed machining spindles specify it. The trade-off is axial capacity and axial stiffness, so 15° is the wrong angle for a heavy thrust position. Angles must be matched across a spindle stack; a 15° bearing paired against a steeper one will be unloaded and skid.

Published ratings and mounting data

None are published on this listing. Load ratings, limiting speed, ball complement and preload force are all series-specific, and until the series digit is resolved by measurement any figure quoted here would be a guess dressed as a specification. No cage code or preload class appears in the designation as marked either, so neither is claimed.

Interchange guidance

Candidate ISO equivalents, subject to the measurement above: 7016C-T-P4S if the bearing is a 2MM9116WI, or 71916C-T-P4S if it is a 2MM9316WI. Both are 15° parts. Note that Barden’s 116-series bearing occupies the same 80 × 125 × 22 envelope as 7016C, so a Barden 116-series bearing may be an alternate if the 9100 reading is confirmed. Fafnir spindle bearings are now branded Timken.