NTNUCFU-2.1/4Four-Bolt Square Flange Ball Bearing Unit, 2-1/4 in Bore, Setscrew Lock, 5-5/8 in Square Bolt Centres, Cast Iron, Contact Seal with Flinger, Relubricatable

Product Description

What this part is

An NTN Ultra-Class mounted ball bearing unit for a 2-1/4 in shaft in a four-bolt square flange housing. The insert is a single-row self-aligning ball bearing with a spherical outer diameter and an extended (wide) inner ring, clamped to the shaft with setscrews; the spherical seat in the housing lets it swivel to absorb initial shaft misalignment. A flange unit bolts to a vertical face, gearbox wall or bulkhead and the shaft passes through the mounting surface.

Decoding the designation

NTN’s mounted-unit codes carry the housing shape. UC is the insert: wide inner ring, setscrew lock, spherical OD. The letters after it are the housing: UCP pillow block, UCF four-bolt square flange, UCFL two-bolt oval flange, UCFC round flange, UCT take-up, and UCFU is NTN’s Ultra-Class four-bolt square flanged unit, listed in NTN’s own catalogue as “Ultra-Class Four Bolt Flanged Unit with Set Screw, UCFU Type” with Type given as “4-Bolt Square Flanged Unit”. The number is the shaft size in inches, so 2.1/4 is a 2-1/4 in bore. Internally the unit is NTN insert A-UC212-204D1 in housing FU212D1V50, which is why the metric 212 series appears on the paperwork of an inch-bore part.

A two-bolt diagonal footprint is a UCFL and a round flange is a UCFC; neither bolts to a UCFU pattern. The UCFU square bolt centres are 5-5/8 in.

What Ultra-Class buys you

Ultra-Class is NTN’s upgraded mounted-unit line: a combined elastomeric contact seal working with an outer flinger that throws debris and liquid away from the seal lip before it reaches the raceway. On dusty or wash-adjacent duty such as grain, aggregate and packaging washdown perimeter, that flinger keeps contamination out of the raceway. Seal material is nitrile rubber; the housing is black-oxided cast iron.

What these specs mean in practice

Setscrew locking carries a 147 lb·in maximum tightening torque. Under-torqued setscrews let the shaft creep and damage the bore; over-torqued ones distort the inner ring and consume the running clearance.

Non-expansion: the insert is axially fixed. On a two-bearing shaft one position is fixed and the other floats, so that thermal growth does not load both bearings axially.

Relubricatable through a housing fitting, so it is greased on a schedule rather than run on the factory charge alone.

2,500 rpm maximum and a −40 to 250°F operating range suit conveyors, fans and augers, including unheated outdoor plant.

Open end type, one-piece cast iron housing. Open means the shaft passes right through; a covered shaft end is the closed-cover variant.

Published ratings and dimensions

Bore (d): 2-1/4 in / 57.150 mm. Housing style: four-bolt square flange, cast iron, one piece, black oxide, open end. Flange overall (L): 6.8750 in / 174.6 mm square. Bolt hole centres (J): 5.6250 in / 142.9 mm square. Bolt hole diameter (N): 0.6719 in / 17.1 mm. Insert width (B): 2.5630 in / 65.100 mm. Flange thickness and pilot dimensions: A 2.0938 in, A0 2.9063 in, A1 0.8125 in, A2 1.3438 in, S 1.0000 in, F 0.2441 in. Dynamic load rating: 11,803 lbf / 52.50 kN. Static load rating: 8,093 lbf / 36.00 kN. Maximum rotational speed: 2,500 rpm. Operating temperature: −40 to 250°F (−40 to 120°C). Weight: 8.379 lb / 3.800 kg. Locking device: set screw, 147 lb·in max tightening torque. Seal: contact seal, nitrile rubber, with outer flinger. Lubrication: relubricatable. Performance class: light duty, NTN’s classification for the UCFU housing series. Replacement insert: NTN A-UC212-204D1; housing FU212D1V50.

Quantity and configuration

Price is per unit. New old stock, made in Japan. Each unit is supplied complete, insert already fitted in the housing, setscrews in place. Mounting bolts are separate items.

Interchange guidance

Inch-bore four-bolt square flange units are widely cross-referenced across makers, and the UC insert dimensions are an industry standard. For a 2-1/4 in bore, NTN UCF212-204 (standard seal), FYH UCF212-36, Asahi UCF212-36, Browning VF4S-236, Dodge F4B-SC-204 and SealMaster SF-36 are the usual four-bolt flange units; confirm the bolt centres (5-5/8 in square here) against your existing plate before substituting. UCFU-2.1/4M is the metric-carton marking of the same unit. Insert-only replacement is NTN A-UC212-204D1 or the standard UC212-204, which suits any UCF/UCFU/UCFL/UCFC housing in the 212 size.