McGillFC4-25K-1-7/16Four-Bolt Flange Mounted Ball Bearing Unit, 1-7/16 in Bore, Nylon Insert Race, K-LOK Shaft Locking, Relubricatable

Product Description

What this part is

The FC4-25K-1-7/16 is a four-bolt FLANGE mounted ball bearing unit with a 1-7/16 in bore. A flange unit bolts to a vertical face, bulkhead or machine end plate, and the shaft runs perpendicular through the mounting — the opposite arrangement to a pillow block, and the answer where there is no flat base to bolt down onto.

What these specs mean in practice

What makes this one different is the NYLA-K construction, and the record previously said nothing about it. On a NYLA-K unit the ball bearing insert does not seat directly on machined cast iron. It sits in a NYLON race inside the cast housing — visible as the black polymer ring in the photographs. That polymer seat does two useful things a rigid iron bore cannot. It lets the insert swivel slightly to take up shaft-to-housing misalignment, so the flange can be bolted to a face that is not perfectly square to the shaft without edge-loading the bearing. And it damps shock and vibration into the housing instead of transmitting it straight through into the structure, which is why these units turn up on screens, fans and other equipment that shakes. It also breaks the metal path between shaft and housing.

Decoding the designation

The K in the designation is McGill’s K-LOK patented shaft locking device — the supplied instruction leaflet is titled for McGill mounted ball bearings “with patented K-LOK and CENTRIK-LOK shaft locking devices”. A K-LOK grips the shaft over a broad area rather than digging in at a single point like a plain setscrew, so it resists creep and does less damage to the shaft, and it can be released and relocated. That matters on a driven shaft where a setscrew-locked insert would eventually work loose and burr the shaft.

Installation and setup notes

The housing carries a grease fitting, so the unit is relubricatable in service rather than sealed for life.

Because it locates on a plain, undersized commercial shaft, no shoulder, keyway or interference fit is needed — but McGill’s own instructions are explicit that the shaft must be within the specified diameter tolerance for the locking device to grip properly, so check the shaft rather than assuming nominal. On a long shaft that grows with temperature, do not fix both ends; leave one bearing free to float.

Quantity and configuration

Supplied as a complete housed assembly — cast iron flange housing, nylon race, insert and locking collar — in its original McGill carton with the installation and lubrication leaflet.

Interchange guidance

The NYLA-K mounted line has since moved to MB Manufacturing, so the same designations are now found under that name, and McGill’s other bearing products passed to Regal Rexnord. Also written FC4-25-1-7/16, FC4-25K-1-7/16, FC4251716 and FC4 25K 1-7/16.