Nachi7206BMUC3Single-Row Angular Contact Ball Bearing — 30 x 62 x 16 mm, 40° Contact Angle, Machined Brass Cage, C3 Clearance, Open

Product Description

What this part is

A Nachi 7206BMUC3 single-row angular contact ball bearing. The inner and outer raceways are ground at a set contact angle, so the ball load line runs at an angle to the bearing axis. That lets the bearing take a combined radial and axial load, and it lets a larger ball complement be fitted than a deep groove bearing of the same envelope — but the axial load can only be taken in one direction.

Decoding the designation

7206 is the ISO base number: 72 series, bore code 06, giving 30 mm bore x 62 mm OD x 16 mm width. B is the contact angle code and on this series it means 40° — the high-angle build, as against the 15° C and 30° A angles in the same envelope. MU is the cage: a machined brass cage. C3 is the internal clearance class, greater than normal. T103K is a Nachi internal grease and design specification code rather than a catalogue dimension code, and is retained here as a search term. Also written 7206B, 7206 BMU C3, 7206-B-MU-C3 and 7206BMU.

What these specs mean in practice

The 40° contact angle is the field that decides whether this bearing suits your machine, and it is the field most often ignored. A 40° bearing carries far more thrust and far less pure radial load than the 15° version of the same number, and it is stiffer axially and softer radially. A 7206B and a 7206C are the same 30 x 62 x 16 mm envelope and are not substitutes — fitting the wrong angle changes the load split between paired bearings and can overload one of the pair. The machined brass cage tolerates higher speed, higher temperature and marginal lubrication better than a pressed steel cage, and it is the cage you want if the bearing sees vibration or shock; it is also the reason the bearing costs more than a plain 7206. C3 clearance is chosen deliberately, usually because the inner ring runs hot relative to the housing or has an interference fit that would close a normal-clearance bearing up — a C3 bearing in a normal-clearance application will run with more play than intended, and a normal-clearance bearing in a C3 application will run hot. Clearance mismatch fails both ways.

Published specifications

Bore (d): 30 mmOutside diameter (D): 62 mmWidth (B): 16 mmContact angle: 40° (B)Rows: 1Cage: machined brass (MU)Internal clearance: C3, greater than normalClosure: open, no seal or shieldPrecision class: ABEC 1 / ISO P0 (normal)Thrust capacity: one direction onlyCountry of manufacture: JapanEAN: 4991893838831

Fitting notes

A single angular contact bearing must be axially located against a shoulder or a nut on the side that takes the thrust; it cannot float. Because it takes thrust one way only, it is normally installed against a second bearing — back to back for maximum moment stiffness, face to face where alignment is imperfect, or in tandem where all the thrust is one way. Watch the mounting direction: the wide-shoulder face of the outer ring is the load-carrying face and installing the bearing reversed removes the thrust capacity entirely. This is a normal-precision, non-universally-ground bearing, so two of them are not a matched duplex pair — a matched pair needs the DU / universally ground designation and will have its preload ground in.

Interchange guidance

The ISO base number 7206B is common to Nachi, NSK, NTN, Koyo, SKF, FAG and others, so the 30 x 62 x 16 mm envelope with a 40° angle is dimensionally interchangeable, subject to matching the cage and the clearance. Watch the angle codes across schemes: SKF writes 40° as B and 25° as AC; NSK uses A for 30°, C for 15° and A5 for 25°. Cage designations that mean machined brass elsewhere include M, MB and MA. Related sizes that are not equivalents are 7206C (15°), 7206A (30°) and 7206 with a pressed steel cage or normal clearance — the same envelope, a different part.