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. Unlike a pillow block, 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 tell you the housing shape, so read them carefully — this is the single most common cause of a wrong-part return in this product family. 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 — confirmed in NTN’s own catalogue, which lists this exact item as “Ultra-Class Four Bolt Flanged Unit with Set Screw, UCFU Type” and its Type as “4-Bolt Square Flanged Unit.” So UCFU is square, not oval and not round. The number is the shaft size in inches: 2.1/4 = 2-1/4 in bore. Internally the unit is NTN insert A-UC212-204D1 in housing FU212D1V50, which is why the metric 212 series shows up on the paperwork of an inch-bore part.

Correcting the source data

The source title said only “Flange Mount Bearing Unit,” which is true but not specific enough to buy from — there are three different flange shapes in this family and they share no bolt pattern. It has been corrected to four-bolt square flange on NTN’s own designation, with the 5-5/8 in square bolt centres published so the footprint can be checked before ordering. If your existing unit has two bolts on a diagonal it is a UCFL, and if it has a round flange it is a UCFC; neither will bolt to a UCFU pattern.

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 — grain, aggregate, packaging washdown perimeter — that flinger is the difference between a bearing that survives and one that grinds itself out in a season. Seal material is nitrile rubber; the housing is black-oxided cast iron.

What these specs mean in practice

Setscrew locking with a 147 lb·in maximum tightening torque. Torque them properly and evenly — under-torqued setscrews let the shaft creep and destroy the bore; over-torqued ones distort the inner ring and kill the running clearance.Non-expansion: the insert is axially fixed. On a two-bearing shaft only one position may be fixed and the other must be free to float, or thermal growth loads both bearings axially. Pair this with a floating unit at the other end.Relubricatable through a housing fitting, so it can be greased on a schedule rather than run to failure on the factory charge.2,500 rpm maximum and a −40 to 250°F operating range — comfortable for conveyors, fans and augers, and the temperature range is wide enough for unheated outdoor plant.Open end type, one-piece cast iron housing. Open means the shaft can pass right through; if you need the shaft end covered, that is the closed-cover variant, not this one.

Published ratings and mounting data

Bore (d): 2-1/4 in / 57.150 mmHousing style: four-bolt square flange, cast iron, one piece, black oxide, open endFlange overall (L): 6.8750 in / 174.6 mm squareBolt hole centres (J): 5.6250 in / 142.9 mm squareBolt hole diameter (N): 0.6719 in / 17.1 mmInsert width (B): 2.5630 in / 65.100 mmFlange thickness / 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 inDynamic load rating: 11,803 lbf / 52.50 kNStatic load rating: 8,093 lbf / 36.00 kNMaximum rotational speed: 2,500 rpmOperating temperature: −40 to 250°F (−40 to 120°C)Weight: 8.379 lb / 3.800 kgLocking device: set screw, 147 lb·in max tightening torqueSeal: contact seal, nitrile rubber, with outer flingerLubrication: relubricatablePerformance class: light duty (NTN’s own classification for the UCFU housing series)Replacement insert: NTN A-UC212-204D1; housing FU212D1V50

Quantity and configuration

Price is per unit; two are in stock, enough for both ends of one shaft. New old stock, made in Japan — unused, but packaging may show age and the carton has been handled. Each unit is supplied complete, insert already fitted in the housing, setscrews in place. Mounting bolts are not included.

Interchange guidance

Inch-bore four-bolt square flange units are heavily cross-referenced across makers, and the UC insert dimensions are an industry standard, so the equivalents at 2-1/4 in bore include NTN’s own UCF212-204 and UCFX12-204, UCFU-2.1/4M (metric-carton marking of the same unit), FYH UCF212-36, Asahi UCF212-36, Timken VF4S-2.1/4, Browning VF4S-236, Dodge F4B-SC-204 class and SealMaster SF-36. 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 — so a failed bearing does not mean a new housing. Confirm bolt centres (5-5/8 in square here) against your existing plate before substituting another maker’s flange.