NTNBST40X72-4BDBTTP4Ball Screw Support Bearing, 60° Contact Angle, P4 Precision, 40 x 72 mm, 15 mm per Row — DBTT Matched Arrangement

Product Description

What this part is

An NTN BST-series angular contact thrust ball bearing for ball screws: 40 mm bore, 72 mm outside diameter, 15 mm width per row, 60° contact angle, P4 precision, open. BST bearings exist for one job — supporting the end of a ball screw on a machine tool or precision actuator — and the whole design is bent toward that job.

The 60° contact angle is the entire point

A general-purpose angular contact bearing runs 15°, 25° or 40°. A ball screw support bearing runs 60°, and that is a deliberate and extreme choice.

A ball screw converts motor rotation into linear force. The reaction to that force is almost entirely axial along the screw, with very little radial component — the screw is normally supported radially at the nut and at a second bearing. So the bearing at the screw end needs enormous thrust capacity and, more importantly, enormous axial stiffness.

Increasing the contact angle to 60° steers nearly the whole load path into the axial direction, which is what produces the very high thrust capacity and axial rigidity this family is bought for.

Why axial stiffness rather than just capacity: any axial deflection at the screw end translates directly into positioning error at the tool. A machine’s repeatability and its ability to reverse without lost motion depend on the screw-end bearing not moving under load.

Decoding the designation

BST: NTN’s angular contact thrust ball bearing series for ball screw supports.

40X72: 40 mm bore, 72 mm outside diameter.

-4B: internal design variant. The commonly traded sibling at the same boundary dimensions is the -1B, and it is a separate internal design, so the design code is matched against the machine’s parts list.

DBTT: a four-row matched arrangement. In NTN’s scheme DB is duplex, DBT is triple, and DBTT is quadruple — four bearings ground and matched as one set. In NTN’s own equivalent-load table the DBTT arrangement is the one in which three rows bear axial load.

P4: ABEC 7 precision class.

Published data for this envelope

Bore (d): 40 mm.

Outside diameter (D): 72 mm.

Width per row (B): 15 mm.

Contact Angle: 60°.

Precision Class: P4 / ABEC 7.

Closure Type: Open.

Arrangement / Configuration: DBTT, four-row matched set.

Internal design: 4B.

Rolling Elements: steel balls.

Unit Quantity: 1 Pc.

Quantity and configuration

Individual BST40X72-4B bearings, sold by the piece. DBTT designates a four-row matched arrangement, and the 15 mm dimension is the width of one row, so a complete four-row DBTT stack measures roughly 60 mm. Individual bearings suit replacing a single row or building a DB or DBT stack of like parts.

Mounting data

Preload in a matched stack is established by the ground ring faces, so spacer, shoulder and locknut faces bear directly on the preload.

Interchange guidance

Search forms include BST40X72-4BDBTTP4, BST-40X72-4B-DBTT-P4, BST40X72-4B, BST40X72 4B DBTT P4, BST40X72, BST 40X72. Related NTN builds at the same envelope: BST40X72-1BP4 (single), BST40X72-1BDBP4 (duplex), BST40X72-1BDBTP4 (triple), BST40X72-1BDTFTP4 (quadruple, DTFT arrangement), BST40X72-1. Equivalent ball screw support bearings at 40 × 72 mm with a 60° angle are catalogued by NSK (TAC series), FAG (BSB series) and INA (ZKLF/ZKLN families, which use a different mounting concept). Contact angle, precision class, internal design code and arrangement are all matched before substituting — on a ball screw end, all four matter.