NDHQ20206DTL3AMatched Tandem Set, Angular Contact Ball Bearings 30 x 62 x 16 mm, 15 Degree Contact Angle, ABEC 3 Quiet Grade, Open, 2 Pcs

Product Description

What this part is

A matched tandem set of two New Departure Hyatt angular contact ball bearings in the 7206 envelope — 30 mm bore, 62 mm outside diameter, 16 mm width per bearing. Open, 15° contact angle, ABEC 3 tolerance to NDH’s quiet-running selection. The pair is ground together as one set to sit side by side facing the same way, roughly doubling the thrust capacity of a single-direction position. New old stock American product.

Decoding the designation

20206 — NDH’s number for the ISO 7206 size, 30 x 62 x 16 mm. The 20-series prefix is the 15° angular contact family; the 30-series is the steeper 40° build.
Q — NDH quiet-running selected series, screened for low noise and vibration.
DT — duplex tandem. Two separate single-row bearings ground as a matched set to be mounted facing the same direction. Not a double-row bearing.
L3 — NDH tolerance grade, equivalent to ABEC 3.
A — NDH internal variant suffix, carried for identification.

What these specs mean in practice

Tandem mounting is the answer when one-direction thrust exceeds what a single bearing will take. Both bearings face the same way and share the axial load roughly equally, so capacity climbs — in that one direction only, so the shaft still needs something opposing at the other end. That is the opposite trade from a back-to-back pair, which handles reversing thrust and moment loads without adding capacity in either direction. The 15° contact angle keeps ball loading close to radial, limiting heat and favouring speed at the cost of thrust capacity against a 40° build; the tandem pairing is exactly how that thrust capacity is recovered without giving up speed. The Q quiet-running selection matters where the bearing is close to the operator or to a measuring head — screened rings and balls make less noise and pass less vibration into the structure, which is why this grade turns up on electric motors, fans, dental and medical equipment and instrument drives.

Quantity and configuration

2 Pcs — a matched tandem set of two bearings, ground together and shipping together. Not two independent bearings; splitting the set loses the matching.

Fitting notes

Both bearings go in facing the same direction, wide land of each outer ring toward the thrust. Fitting one reversed turns the set into a back-to-back pair with entirely different load behaviour and no shared thrust capacity. Look for the grinding marks across the ring faces, usually a scribed line or V, and line them up on assembly — that is the orientation the set was ground in. Seats must be clean, ground and burr-free; interference fit adds to whatever preload the set carries, so check sizes against the drawing. Never press through the ball complement. A quiet-grade bearing is only as quiet as its mounting, so avoid hammer blows and a distorted housing.

Interchange guidance

New Departure Hyatt was General Motors’ bearing division and is long out of production, so cross-reference by the ISO number: 7206 at 15°, supplied as a tandem duplex set. Genuine same-angle equivalents include SKF 7206 CD/P4ADT, FAG B7206-C-T-P4S-DT, NSK 7206C in a DT set and Fafnir/Timken 2MM9106WI CR DT — note those are super-precision grades and therefore tighter than the ABEC 3 supplied here. Related sizes fill the identical 30 x 62 x 16 mm envelope at other contact angles: 7206AC is 25°, 7206B is 40°, and NDH’s own 30206 is the 40° version of this number. Different parts, not substitutes. The arrangement code matters as much as the angle — a DB or DF pair of this size handles reversing thrust rather than doubling it in one direction.