FafnirMM20BS47DUHBall Screw Support Bearing – 20 mm ID, 47 mm OD, 15 mm Width, Open, 60° Contact Angle, Heavy Preload, ABEC 7/9 P4S

Product Description

What this part is

Fafnir MM20BS47 DUH is a super-precision ball screw support bearing supplied as a matched duplex pair. Bore Diameter: 20 mm. Outside Diameter: 47 mm. Overall Width: 15 mm. Contact Angle: 60°. Bore Type: Straight. Closure Type: Open. Rolling Elements: Ball. Number Of Rows: 1 per bearing. Bearing Material: Bearing steel. Timken files it in the Fafnir Single Row Ball Screw Support Bearings (MM-BS) range.

Decoding the designation

MM — Timken Fafnir super-precision grade P4S. Timken’s Machine Tool Catalog sets P4S running accuracy at ABEC 9 / ISO P2 while holding the remaining bearing features at ABEC 7 / ISO P4.

20 — bore diameter in millimetres.

BS — ball screw support. Timken builds this range with steep contact angles specifically for servo-driven ball screw end mountings.

47 — outside diameter in millimetres.

DUH — duplex universal, heavy preload. Two bearings ground as a matched set with flush faces, so the pair mounts back to back, face to face or in tandem.

What these specs mean in practice

Contact Angle: 60°. A ball screw end mounting takes almost pure thrust, so the contact line is laid over steeply to put the load through the balls axially. That is what separates this family from a 15° or 25° spindle bearing on the same envelope.

Dynamic Load Rating: 24,900 N. Static Load Rating: 24,900 N. Timken publishes the two figures as equal for this bearing. Steep-angle thrust types sit in the band where static capacity meets or exceeds dynamic, so the pairing is characteristic of the family rather than a transcription fault.

Limiting Speed: 4,700 rpm grease; 9,400 rpm oil. Lubricant: Grease or oil. The 60° angle that buys axial stiffness also caps speed well below a spindle bearing of the same bore.

Preload: Heavy. Heavy preload removes axial play from the screw end and holds positioning accuracy through load reversals, which is the whole point of a preloaded ball screw mounting.

Precision Class: ABEC 7/9 / P4S.

Mounting data

Bore Diameter: 20 mm. Outside Diameter: 47 mm. Overall Width: 15 mm. Shaft Backing Shoulder Diameter: 33.492 mm (1.3186 in). Housing Backing Shoulder Diameter: 34.493 mm (1.358 in). Maximum housing fillet radius that the bearing corners will clear: 0.8 mm (0.031 in). Item Weight: 0.24 kg (0.52 lb) for the matched pair, 0.12 kg per bearing.

Quantity and configuration

Unit Quantity: 2 Pcs. Mounting Arrangement: Duplex universal (DU). Series: MM-BS. Base Number: MM20BS47. GTIN: 087796052192. Harmonization Code: 8482.10.50.

Interchange guidance

Ball screw support bearings are a distinct family and the 60° angle is the matching criterion. The 20 x 47 x 15 mm equivalents from other makers are listed in the cross-reference fields. A 7204-size angular contact bearing shares neither the angle nor the axial rating and is a different part.