Mounted Bearing Nomenclature: How to Read a Part Number

A mounted bearing part number is not an arbitrary code. Manufacturers build it from a small set of components — housing family, locking style, duty level, and bore size — and once you can read those components, you can identify most units from the number alone, or reconstruct a number from a unit on the machine. This guide decodes the two systems we are asked about most, Sealmaster and Browning, using designations verified against our own catalog data.

The anatomy of a mounted bearing number

Most mounted ball bearing catalog numbers follow the same skeleton: a letter prefix that names the housing and how the bearing insert locks to the shaft, followed by a number that states the bore — the shaft diameter the unit fits. In Browning's system the locking style is a letter inside the prefix itself; in Sealmaster's system the base prefix carries the housing and duty level. Material variants add letters ahead of the housing code: Browning uses S for stainless and SS for stamped steel, while Sealmaster's corrosion-resistant line leads with CR.

Worked example: VPS-216 combines Browning's VP pillow-block prefix with S for setscrew locking; the trailing 16 states a 1-inch bore. NP-16 is a Sealmaster normal-duty pillow block, also 1-inch bore. Same unit function, two vocabularies.

Browning housing prefixes

The first letters of a Browning number name the housing family. The final letter of the prefix is the locking style, listed in the second table — so VPS, VPE, and VPB are one housing (a two-bolt pillow block) with three different shaft-locking mechanisms.

Setscrew locking holds the shaft with screws through the insert's inner ring and is the default for general duty. An eccentric collar locks by cam action when spun against the inner ring, resisting vibration loosening in reversing applications. BOA is Browning's concentric collar system: it clamps evenly around the shaft, which keeps the assembly balanced at higher speeds and avoids the point contact of setscrews on the shaft surface.

Sealmaster housing prefixes

Sealmaster encodes the duty level into the housing prefix: N is the normal-duty Gold Line, M marks medium duty, and the CR prefix ahead of any housing code marks the corrosion-resistant line. Flange units split by bolt pattern exactly as Browning's do — the difference is only in which letters say so.

Bore numbers: sixteenths of an inch

The number after the prefix states the bore in sixteenths of an inch: divide by 16 to get the shaft size. A -16 unit fits a 1-inch shaft, a -20 fits 1-1/4 inch, and a -32 fits a 2-inch shaft. Sealmaster states the sixteenths directly (NP-16); Browning places a catalog-series digit ahead of them, so VPS-216 reads as series 2 with a 16-sixteenths — 1-inch — bore. This one rule decodes the size of nearly every inch-series mounted bearing from Sealmaster, Browning, and their competitors.

For the full fractional-to-decimal-to-metric table, see the Shaft Size Conversion Chart.

When the number does not decode cleanly

Real catalogs carry exceptions: transitional families, dual-meaning prefixes, and legacy designations that predate the current system. If a number on your equipment does not match the tables above — or matches two of them — send it to us through the cross-reference form and we will identify the unit and its current replacement. You can also browse the mounted bearings catalog by housing type directly.