Fafnir2MM9126WIDULSuper Precision Angular Contact Ball Bearing 130 x 200 x 33 mm, 15° Contact Angle, ABEC 7, Phenolic Cage, Single Universally Ground, Medium Preload

Product Description

What this part is

A single super precision angular contact ball bearing in the 7026 envelope — 130 mm bore, 200 mm outside diameter, 33 mm width. Spindle grade, phenolic caged, universally ground so it develops a medium preload when clamped against a matching bearing.

Decoding the designation

2MM — Fafnir super precision series with a 15° contact angle. The MM prefix carries P4S tolerance (ABEC 7 running accuracy with tighter ABEC 9 bore and outside diameter control).
9126 — the Fafnir 91xx block maps to the ISO 70xx dimension series, so this is the 7026 envelope: 130 x 200 x 33 mm.
WI — Fafnir super precision angular contact spindle bearing.
CR — phenolic (cotton-reinforced laminate) cage, outer ring land riding.
SUM — single, universally ground, medium preload. The S element is what makes this a one-piece item: an SU bearing is a single universal bearing, where a DU designation would be a factory-matched pair.

What these specs mean in practice

A 15° contact angle keeps the ball from climbing far up the raceway shoulder, so ball spin, friction and heat generation are all lower and the permissible speed is higher than a 25° bearing in the same envelope. The trade is axial capacity and axial stiffness, both of which the shallower angle reduces. It is the right angle for a spindle whose limit is rpm rather than cutting force.

The phenolic outer-land-riding cage supports that: low density means low centrifugal cage stress at high rpm, and the laminate holds a small oil reserve that carries the bearing through a brief lubrication interruption. It is heat-sensitive, so clean lubrication and a light grease fill matter.

Medium preload, once the bearing is paired, gives more axial and moment stiffness than light preload and a little more heat. Universal grinding means you get that preload simply by clamping two SUM bearings of this designation together — no shim stack, no spacer calculation.

Quantity and configuration

What ships is one bearing. That is worth being clear about, because the SU prefix is easily read as a set. A single universal bearing is exactly what you want if you are replacing one damaged half of an existing spindle pair, adding a third bearing to make a triplex stack, or building up an arrangement to your own preload scheme. If you need a complete pair, order two of this designation, or ask — matching stock may be on the shelf.

Fitting notes

Grind the shaft journal and housing bore to a precision that matches the bearing, with runout and roundness held to a few microns and abutment faces square. Mount with controlled heat or a press acting only on the ring being fitted; never let mounting force pass through the balls. If you are combining this bearing with an existing one, both must be the same designation, the same contact angle and the same cage — a 2MM and a 3MM bearing in one stack will not preload as intended. Lubricate with a spindle grease or an oil mist or oil-air system rated for the intended speed and keep the fill light.

Interchange guidance

Fafnir super precision now ships under the Timken brand and the Fafnir numbers remain in cross-reference use. Same-envelope 15° equivalents include NSK 7026C, FAG B7026-C-T-P4S, SKF 7026 CD/P4A and NTN 7026C in the corresponding precision grade; C denotes 15° in all three of those schemes, so those are true angle matches as well as dimensional matches. The 25° Fafnir sibling is 3MM9126WI — a different bearing, and not interchangeable inside a preloaded stack.