NDH20204DTL5E9Matched Tandem Set, Angular Contact Ball Bearings 20 x 47 x 14 mm, 15 Degree Contact Angle, ABEC 5, Open, 2 Pcs

Product Description

What this part is

A matched tandem set of two New Departure Hyatt angular contact ball bearings in the 7204 envelope — 20 mm bore, 47 mm outside diameter, 14 mm width per bearing. Open, 15° contact angle, ABEC 5 precision. The two bearings are ground together as one set to sit side by side facing the same way, which roughly doubles the thrust capacity of a single-direction position. New old stock American spindle-grade product.

Decoding the designation

20204 — NDH’s number for the ISO 7204 size, 20 x 47 x 14 mm. The 20-series prefix is the 15° angular contact family; the 30-series is the steeper 40° build.
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.
L5 — NDH tolerance grade, equivalent to ABEC 5.
E9 — NDH internal ring and grinding variant suffix, carried for identification.

What these specs mean in practice

Tandem mounting is what you reach for when thrust in one direction is more than a single bearing will take. Both bearings face the same way and share the axial load roughly equally, so capacity climbs — but only in that one direction, so the shaft still needs something opposing at the other end. That is the opposite trade to a back-to-back pair, which handles thrust both ways and resists moment loads without adding capacity in either direction. The 15° contact angle keeps ball loading close to radial, which limits heat and favours speed while conceding thrust capacity to a 40° build; pairing in tandem is precisely how the thrust capacity is recovered without losing the speed. ABEC 5 running accuracy is a clear step above standard and only reaches the shaft if the seats are ground and true to match — a worn housing bore throws it away.

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. Lubricate sparingly with a spindle grease or run oil-air.

Interchange guidance

New Departure Hyatt was General Motors’ bearing division and is long out of production, so cross-reference by the ISO number: 7204 at 15°, supplied as a tandem duplex set. Genuine same-angle equivalents include SKF 7204 CD/P4ADT, FAG B7204-C-T-P4S-DT, NSK 7204C in a DT set and Fafnir/Timken 2MM9104WI CR DT. Related sizes fill the identical 20 x 47 x 14 mm envelope at other contact angles — 7204AC is 25°, 7204B is 40°, and NDH’s own 30204 is the 40° version of this number. Different parts, not substitutes. The arrangement code matters equally: a DB or DF pair of this size handles reversing thrust rather than doubling it in one direction, and will not do this job.