NDHQ20218DTL7ASuper Precision Angular Contact Ball Bearing Matched Tandem Pair DT 90x160x30mm 15 Degree ABEC 7 Phenolic Cage Light Preload

Product Description

What this part is

A matched tandem pair of New Departure Hyatt Q-series super-precision angular contact ball bearings on the 7218 envelope: 90 mm bore, 160 mm OD, 30 mm wide each, 60 mm stacked. This is large-spindle hardware — heavy milling and boring spindles, big grinding heads and vertical shafts that carry a substantial one-way thrust at speed.

Decoding the designation

Q — NDH precision angular contact ball bearing line20218 — NDH size and design code; the 218 bore code is 90 mm, the 7218 envelopeDT — duplex tandem, a factory-matched pair mounted facing the same directionL — light preload7A — NDH variant suffix carried on the carton; kept as a search term rather than published as a spec, as NDH’s definition is not published
The carton cross-references 7218C-T-P4 and Fafnir 2MM218WI-CR agree on 15° contact angle, phenolic cage and P4 / ABEC 7 class.

What these specs mean in practice

In a tandem pair both bearings face the same direction, so their thrust capacities add — roughly double a single bearing — but in one direction only. The shaft still needs a second bearing or a shoulder to locate it the other way. Mounting a tandem set back-to-back would give two-way location while throwing away the doubled capacity and the intended load sharing, so the arrangement is not a matter of preference. Light preload keeps friction and heat low, which is what allows a bearing this size to run at speed; the 15° contact angle pushes the speed ceiling higher still at the cost of thrust capacity per bearing, which is exactly why the design stacks two in tandem.

Published specifications

Bore: 90 mmOutside diameter: 160 mmWidth: 30 mm each bearingTotal width mounted as a tandem pair: 60 mmContact angle: 15°Tolerance class: P4 / ABEC 7Preload: lightCage: phenolicArrangement: duplex tandem (DT)Rows: single row eachClosure: open

Quantity and configuration

Two bearings, supplied as the factory-matched tandem set. Mount both facing the same direction with the high shoulders taking the thrust. Do not split the pair or substitute a bearing from another set — the even load sharing comes from the matched grind.

Fitting notes

Identify the high-shoulder face of each outer ring before pressing, and mark the faces so the arrangement can be reproduced at the next rebuild. Clamp the pair as a unit; leaving one ring unclamped puts the whole thrust load on one bearing. Mount clean, press only on the ring being fitted, and never drive mounting force through the balls — on a 90 mm bore the required press force is high enough to do real damage if it is applied wrongly. Lubricate sparingly with a spindle grease or oil-air feed matched to the speed.

Interchange guidance

Same-specification alternatives are 7218-envelope 15° ABEC 7 phenolic-cage light-preload bearings supplied as a matched tandem pair, including 7218C-T-P4 tandem sets and the Fafnir 2MM218WI-CR in a tandem arrangement. Related but NOT interchangeable: DB or DF pairs of the same size, 7218A5 (25°) or 7218A (30°), medium and heavy preload variants, and any single bearing of this number on its own.