SealMasterMRP-24Two-Bolt Pillow Block Ball Bearing Unit, 1-1/2 in Bore, Setscrew Lock, Cast Iron, Relubricatable, Non-Expansion

Product Description

What this part is

A SealMaster mounted ball bearing unit for a 1-1/2 in shaft — a cast iron two-bolt pillow block, not a flange block. The insert is a self-aligning ball bearing with a spherical outer diameter and an extended (wide) inner ring, locked to the shaft by setscrews. The spherical seat lets the insert swivel in the housing to take up initial shaft misalignment at installation, which is the whole point of a mounted unit: you bolt the housings down to an imperfect frame and the bearings find the shaft.

Decoding the designation

SealMaster (now Regal Rexnord) codes the housing style in the prefix and the shaft size in the number. The number is sixteenths of an inch — so 24 = 24/16 = 1-1/2 in bore, exactly as the listing states. That decode is worth knowing: NP-16 is a 1 in bore, NPL-23 is 1-7/16, NPL-39 is 2-7/16. In the prefix, a trailing P is the pillow-block family (MP medium duty, NP normal/standard duty, NPL low base, MPD/NPD double-lock, SP standard duty heavy housing). Flange units carry an F — SF and SFT are standard-duty four- and two-bolt flanges, MSF is the medium-duty four-bolt flange, MFC and SFC are flange cartridges. Take-ups are ST, MST and STU. There is no pillow block with an F and no flange with a bare P.

Correcting the source data

The source listing called this a “Flange Mount Bearing.” It is not. Every SealMaster designation ending in P at the -24 size is a base-mounted two-bolt pillow block; a flange unit would read SF-24, SFT-24 or MSF-24. This matters commercially, not academically: a flange block bolts through a vertical face or bulkhead with the shaft passing through it, while a pillow block bolts down onto a horizontal base beside the shaft. They are not interchangeable in either direction, and a buyer who needs one and receives the other cannot fit it. The title, short description and attributes here have all been corrected to pillow block.

What we could not confirm — read this before ordering:
MRP is not a prefix published in SealMaster’s own mounted-ball-bearing nomenclature, and Regal Rexnord’s current catalogue returns no MRP series. The published 1-1/2 in bore two-bolt pillow blocks in the same family are MP-24 (medium duty), NP-24 (normal/standard duty, high base) and NPL-24 (low base). The carton marking is retained here as listed rather than silently rewritten. Because the exact series is unconfirmed, we have deliberately left the load ratings, bolt centres and unit weight blank rather than publish figures borrowed from a neighbouring series. If those dimensions decide your purchase, ask us and we will measure the unit on the shelf.

What these specs mean in practice

Setscrew locking: two hardened setscrews at 120° clamp the extended inner ring to the shaft. Simple, field-serviceable, and it tolerates a commercial shaft tolerance — but it can score the shaft and it is less concentric than an eccentric collar or concentric-lock design, so it is the wrong choice for high speed or reversing duty.Non-expansion: the insert is axially fixed in the housing. On a two-bearing shaft only one bearing may be the fixed unit; the other must be free to float, or thermal growth in the shaft will load both bearings axially and destroy them. If both of your positions are non-expansion pillow blocks, that shaft is being preloaded every time it warms up.Relubricatable: SealMaster inserts carry a lubrication hole and dimple in the outer ring, so grease reaches the raceway through the housing fitting rather than only at assembly.Cast iron housing with a self-aligning spherical seat — a general industrial machine element, not a washdown or corrosion-resistant one. For food or wet duty the stainless and coated equivalents (CRPS, PN) are the correct family.

Published mounting data

Bore / shaft size: 1-1/2 in (24/16 in)Housing style: two-bolt pillow block, base mountHousing material: cast ironInsert type: single-row self-aligning ball bearing, spherical OD, extended inner ringLocking method: setscrewExpansion type: non-expansionRelubrication: yes, through housing fittingLoad ratings, bolt centre-to-centre, base-to-bore centreline, overall dimensions and unit weight: not published for the MRP designation — see the note above

Quantity and configuration

Price is per unit. Four units are in stock, so a two-shaft pair or a matched set of four from one production batch is available — useful when you are replacing a whole line shaft rather than one failed position. Each unit ships as housing plus insert, complete; setscrews are fitted. No mounting bolts, shims or take-up frame are included.

Interchange guidance

SealMaster is now part of Regal Rexnord, so current literature and stock appear under that name; older paperwork will say SealMaster, Stephens-Adamson or Gold Line. Two-bolt pillow blocks for a 1-1/2 in shaft are a widely duplicated envelope — Dodge/Baldor P2B-SC-108 and P2B-SCM-108, Link-Belt P3U224, Browning VPS-224, Timken VPB-224, Sealmaster NP-24/MP-24, NTN UCP-1.1/2 and SKF SYH 1.1/2 all serve the same shaft size — but base-to-bore centreline and bolt centres differ between series, so confirm your existing footprint before treating any of them as a drop-in. If you need the bolt pattern matched exactly, send us the dimension between your two existing bolt holes.