NDHQ20210DTX5AAngular Contact Ball Bearing Matched Tandem Set 50 x 90 x 20 mm, Medium Preload, ABEC 5, Phenolic Ball Separator, Set of 2

Product Description

What this part is

An NDH Q20210DTX5A matched set of two single-row angular contact ball bearings, each 50 mm bore by 90 mm outside diameter by 20 mm wide, ground as a tandem set. Two separate bearings rather than one double-row bearing. Phenolic ball separator, rust-preventive slush coating.

Decoding the designation

Q — phenolic ball separator.
202 — dimension-series code corresponding to the ISO 72 series; with bore code 10 this is the ISO 7210 envelope, 50 x 90 x 20 mm.
10 — bore code, five millimetres per step, giving a 50 mm bore.
DT — duplex tandem, faces flush-ground and universally mountable.
X — medium preload. L is light, T heavy, S special, 0 none.
5 — ABEC 5.
A — rust-preventive slush coating.

What these specs mean in practice

In a tandem set both contact lines point the same way, so the two rows share thrust in one direction and axial capacity roughly doubles against a single bearing. A tandem pair locates the shaft in that one direction only, and an opposing bearing elsewhere in the stack sets the other. Back-to-back and face-to-face sets take thrust both ways from one pair, which is the trade a tandem set gives up in exchange for the higher one-way capacity.

Medium preload sits between the light and heavy grades: more axial stiffness and better running accuracy than light, and a lower running temperature and less frictional torque than heavy. ABEC 5 holds bore, outside diameter, width and runout well inside standard tolerances, which is the class New Departure used for machine tool and precision drive spindles. A phenolic separator is lighter and quieter than steel at speed and holds an oil film in its pockets. The rust-preventive slush is a shelf-storage coating rather than a running lubricant, so it sits on the raceways as supplied.

Published specifications

Bore: 50 mm (1.9685 in)
Outside diameter: 90 mm (3.5433 in)
Width per bearing: 20 mm (0.7874 in)
Total width of the tandem stack: 40 mm (1.5748 in)
Rows: 1 per bearing, 2 in the mounted set
Arrangement: duplex tandem (DT)
Preload: medium (X)
Precision class: ABEC 5
Rolling elements: steel balls
Separator: phenolic
Protective coating: rust-preventive slush
Closure: open both faces

Mounting arrangement

Two bearings ship as one matched tandem set. The set’s accuracy comes from the matched face grind, so its preload holds in the supplied orientation with the inner rings clamped against each other and the outer rings clamped equally in the housing. The flush-ground faces make the set universally mountable within the tandem arrangement.

Quantity and configuration

2 Pcs, supplied as one matched tandem set.

Interchange guidance

ISO base number 7210. Searchable forms are Q20210DTX5A, Q-20210-DT-X5A, Q 20210 DT X5A, Q20210DT and 7210DT. New Departure Hyatt was a General Motors division and the line passed to Delphi, so buyers usually arrive from a current designation on the same envelope. On this envelope the arrangement and the contact angle govern substitution: DB back-to-back and DF face-to-face sets carry thrust differently from a tandem set, and preload grades L, T, S and 0 are different parts. Current-brand 7210 tandem sets in a stated contact angle grade are related sizes on the same envelope. Trailing multi-digit blocks such as 5038A are factory deviation numbers, carried as cross-references.