SNFAE250-7CE3DUM-1/2PRSuper Precision Angular Contact Ball Bearing 50x90x20 mm Half of Matched Pair 1 Pc Medium Preload Phenolic Cage ABEC 7

Product Description

What this part is

One super precision angular contact ball bearing from SNFA’s E series — 50 mm bore, 90 mm outside diameter, 20 mm width. The E series is SNFA’s own super-precision spindle family; it is not a rebadged general-purpose bearing. This is a machine tool spindle component.

This is ONE bearing, not a pair

The -1/2PR suffix means half of a pair. The parent designation DUM describes a duplex universally ground matched set for medium preload, and this listing covers a single bearing out of that set. If your spindle needs the full duplex pair, one of these will not do the job on its own. This is stated here, in the title, in the short description and in the Unit Quantity attribute because a buyer expecting two bearings and receiving one is the single most common dispute on parts like this.

Decoding the designation

E – SNFA super precision angular contact series.
250 – SNFA size code for the 50 mm bore, 90 mm OD, 20 mm wide envelope.
7 – ABEC 7 / P4 precision class.
CE – SNFA cage code; a phenolic (resin) cage, externally located.
3 – SNFA’s contact angle code for the 25° variant.
DUM – duplex universally ground, medium preload.
1/2PR – half of a pair, i.e. one bearing.

Correcting the source data

Two corrections. First, the old copy claimed the bearing was “crafted with precision in Italy”. No carton marking or manufacturer publication supports that, so no country of origin is claimed here at all. Second, and more important for anyone cross-shopping: the record carries 7210-A as a cross-reference. In ISO/SKF convention the A suffix denotes a 30° contact angle, while SNFA’s own 3 code reads as 25°. Those two cannot both be right, and reading SNFA’s designation with someone else’s alphabet is exactly how the wrong angle gets published. Reading SNFA’s own scheme, this is the 25° variant, and the equivalent in current SKF super precision terms is the ACD (25°) class rather than the A (30°) class. Treat 7210-A as a size cross-reference for the 50x90x20 envelope only, not as a contact-angle statement. Confirm the angle against the ring marking or with SKF before you commit to a spindle rebuild.

What these specs mean in practice

A 25° contact angle sits at the stiff end of the super precision range. Against a 15° bearing it carries substantially more thrust and gives greater axial stiffness, but it generates more heat and caps out at a lower speed — the classic trade for heavier cutting, boring and drilling duty rather than top-rpm grinding. Medium preload (M) reinforces that bias: more stiffness and better position control than light preload, at the cost of running temperature and bearing life. The phenolic cage is light and self-lubricating and suits oil-mist and oil-air systems well, but it is less tolerant of contamination and sustained high temperature than a machined bronze cage. ABEC 7 sets the running accuracy you can expect at the tool.

Published ratings and mounting data

Dynamic and static load ratings, limiting speed and preload force in newtons are left blank. SNFA as a marque has been absorbed into SKF and no current manufacturer table was located for this exact designation string; the figures circulating on distributor mirrors are provisional at best and frequently belong to the SKF successor part rather than to the SNFA original. An honest gap is more useful here than a borrowed number. Request the values from SKF against the full designation if your calculation depends on them.

Quantity and configuration

One bearing — half of a DUM matched pair. It is not supplied with its partner and cannot be relied on to mate with an arbitrary second bearing of the same designation, because the matching is done at the factory on that specific pair.

Fitting notes

If you are replacing one half of an existing pair, be aware that the surviving bearing has worn and this one has not; most spindle rebuilders replace both. Never mix preload classes in one stack — an M bearing next to an L bearing yields an indeterminate preload and usually a hot spindle. Mount by the marked faces, keep the bearing wrapped until the seats are clean and measured, and never press through the balls.

Interchange guidance

SNFA was acquired by SKF, so current sourcing and technical data route through SKF’s super precision range. The size cross-reference is the 7210 envelope. Before substituting, match the contact angle (25° per SNFA’s own code — verify), the precision class (ABEC 7 / P4), the cage material (phenolic) and the preload class (M). Same envelope is not the same bearing.