NHBBME-21907DLSuper-Precision Angular Contact Ball Bearing Matched Pair – Straight Bore, 35 mm ID, 55 mm OD, 10 mm Width, Open, 25° Contact Angle, Light Preload, Phenolic Cage, ABEC 7

Product Description

What this part is

NHBB ME-21907DL is a duplex matched pair of super-precision angular contact ball bearings, 35 mm bore by 55 mm outside diameter by 10 mm width per bearing, 20 mm across the mounted pair. This is the thin 719 dimension series, the shallowest of the angular contact sections, used where a spindle needs stiffness in a short axial space. Rings and balls are 52100 chrome steel, the cage is fabric-base phenolic laminate riding on the outer ring land, and both bearings are open.

Decoding the designation

Four numbering schemes appear on the carton and all four agree on the angle. NHBB ME-21907DL is the MER-1907 envelope with a duplex light-preload suffix. The ISO reading 71907-E-TPA-P4-DUL gives E for 25° in the Schaeffler scheme, TPA for phenolic laminate, P4 for ABEC 7 and DUL for a duplex universal set at light preload. The Fafnir reading 3MMV9307WI-CR-DUL gives 3MM for 25°, the 9300 series prefix that maps to the ISO 719 family, and CR for a phenolic outer-land-riding cage. The NSK reading 71907 A5 TR gives A5 for 25° and TR for an outer-ring-guided phenolic cage.

What these specs mean in practice

A 25° contact angle carries substantially more thrust than a 15° bearing of the same size and turns more slowly, which suits a spindle or screw-support position where axial load dominates. The phenolic cage runs quietly at speed, holds oil in its own structure and sets the practical temperature ceiling at 120°C. Light preload gives the lowest running friction and heat of the preload ladder while still eliminating internal play.

Quantity and configuration

Two pieces, supplied as one matched pair. The rings are universally ground, so the pair can be clamped back-to-back, face-to-face or in tandem and will develop the specified light preload in any of those arrangements. The set is preloaded rather than clearance-set, so no internal clearance class applies.

Fitting notes

The maximum shaft or housing fillet radius the bearing corners clear is 0.024 in. Inner land diameter is 1.644 in and outer land diameter 1.942 in. Each bearing carries 18 balls of 1/4 in diameter. Oil lubrication suits the phenolic cage at the speeds this section is built for.

Interchange guidance

SKF 71907 ACDGA/P4A is the direct equivalent, matching on envelope, 25° angle, ABEC 7 class and light preload. Fafnir 3MMV9307WI-CR-DUL is the same set in Timken numbering. NSK 71907A5TRDULP4 is the pair; the 71907A5TRSULP4 form of that number is a single universal bearing rather than a pair. A 71907 CD, 71907 C or 2MM9307WI is a 15° bearing on the same envelope, so it is a related size rather than a substitution.