SealMasterNP-9Two-Bolt Pillow Block Bearing Unit, 9/16″ Bore, Setscrew Locking, Non-Expansion, Cast Iron, Felt Seals

Product Description

What this part is

A SealMaster NP-9 mounted ball bearing unit — a two-bolt cast iron pillow block, not a flange unit. The NP series is SealMaster’s normal-duty Gold Line pillow block: a wide-inner-ring ball bearing insert with a spherical outer race, self-aligning in a one-piece cast iron housing, locked to the shaft by two setscrews in the extended inner ring.

Decoding the designation

NP – normal-duty two-bolt pillow block housing (SealMaster MP, NP and MRP are all pillow blocks; SF, SFT and FB are the flange styles)
9 – bore size in sixteenths, so 9/16 in shaft
Non-expansion type: the insert is axially located in the housing, so this end of the shaft is the locating end

Correcting the source data

Earlier copy described this as a flange mount unit. It is a two-bolt pillow block — it bolts to a horizontal surface parallel to the shaft, not to a vertical face perpendicular to it. If you were shopping for a flange, this is not the housing you want.

Published specifications

Shaft size: 9/16 in
Bolt hole spacing, centre to centre: 3-3/4 in
Bolt size: 1/2 in
Base to shaft centre height: 1-3/16 in
Overall length: 5 in · overall height: 2-7/16 in · base width: 1-1/2 in
Housing: cast iron · insert races: 52100 chrome steel
Locking: two setscrews · Seals: felt · Relubricatable via grease fitting
Expansion: non-expansion (locating)

What these specs mean in practice

Setscrew locking is quick to fit and quick to service, but it is a one-direction-friendly lock: it holds well against steady loads and light shock, and it will mark the shaft. On a reversing or heavily shock-loaded drive an eccentric collar or concentric clamping unit holds better. Felt seals suit clean-to-moderately-dusty indoor duty; they are not a wash-down or slurry seal.

Because the insert self-aligns on its spherical outer race, the housing tolerates modest misalignment between mounting surface and shaft — useful on bolted-up steel frames and conveyor side rails. Only one end of a two-bearing shaft should be non-expansion; pair this with an expansion unit at the far end if the shaft will grow thermally.

Quantity and configuration

One complete unit: cast iron housing with the bearing insert, seals and setscrews installed. No shaft, no mounting hardware.

Fitting notes

Check that the 3-3/4 in bolt centres and 1-3/16 in centre height match the frame you are replacing into — SealMaster NPL and MP housings in the same bore size use different centres and heights and will not drop into an NP footprint. Clean the shaft seat, slide the unit on, align the shaft, then tighten both setscrews evenly.

Interchange guidance

Same-bore normal-duty two-bolt pillow blocks from other makers are functionally similar but rarely share the NP footprint, so treat them as related sizes rather than drop-in equivalents unless you have verified the bolt centres and centre height. SealMaster’s own NPL-9 is a related size, not the same housing.