Mounted Bearing Selection Guide

A mounted bearing is a bearing insert and a housing sold as one unit that slips onto the shaft and bolts to the machine. Choosing one is a sequence of decisions: the bearing type that carries the load, the bore that fits the shaft, the housing style that fits the mounting surface, the locking method that holds the shaft, and the seal and housing material that suit the environment. This guide takes each decision in turn and names the mounted bearing series stocked for it.

What do you need to know before choosing a mounted bearing?

Eight things decide the selection: the equipment constraints (shaft diameter and the housing style the machine can take), the load magnitude and direction, static and dynamic misalignment, shaft expansion, noise, vibration and shock loading, the environment, and the bearing type. The load and the shaft size usually settle the bearing type first; the rest of the list refines the housing, lock and seal.

Load direction is either radial (perpendicular to the shaft centerline), thrust (along the centerline) or a combination of the two. Misalignment comes in two forms: static misalignment is a fixed angle from bearings mounted on different planes, and dynamic misalignment is an eccentric shaft rotation from shafting imperfections that changes the angle as the shaft turns. Each bearing type tolerates a different amount of each, and exceeding the limit raises the contact stress between rolling elements and raceways and shortens bearing life.

Ball, tapered roller or spherical roller: which bearing type carries the load?

Ball bearings suit light to moderate loads and run at the highest speeds; roller bearings suit moderate to heavy loads. A mounted tapered roller bearing is set at an angle and accepts heavy radial and thrust loads together, which is why it is the choice for mining, bulk material handling and off-highway equipment. A mounted spherical roller bearing is internally self-aligning and is the type for applications with both static and dynamic misalignment, but it is not suited to higher speeds.

Rated 1 (poor) to 5 (best).

A radial ball bearing makes a small elliptical contact with the raceway, so it generates less friction and heat and has the higher speed range, but that same small contact limits it to light and moderate loads. It has a zero degree free contact angle and takes light thrust only in combination with a radial load. Mounted ball units have external static self-aligning capability: the insert can misalign with respect to the housing, by up to plus or minus 2 degrees on Sealmaster Gold units and plus or minus 1 1/2 degrees on Browning units. Tapered rollers make a line contact, and a double row doubles the number of rolling elements carrying the load; mounted tapered roller units are externally self-aligning in the same way as ball units. Spherical rollers have a barrel profile on a curved raceway, so the rolling elements and raceways move relative to each other and the bearing aligns itself internally; some sliding at that interface is what rules them out of high speed work.

Where a ball bearing cannot reach the required load or life, move up to mounted tapered roller bearings or mounted spherical roller bearings; ball bearings usually cost less for a given shaft size and are considered first. Vibration and shock loading, as in vibratory conveyors and shakers, also favors a roller bearing, because its larger contact area spreads the load. Noise-sensitive equipment such as fans is typically low duty, which makes a mounted ball bearing a good choice, with a concentric lock preferred to keep vibration to a minimum.

How does the shaft size decide the bearing?

The shaft diameter is the bore of the bearing, and it is often fixed by the equipment before any other choice is made. Small diameter shafts carry light loads and point to a ball bearing; higher loads dictate larger shafts and then tapered or spherical roller bearings. Inch-series mounted ball bearings state the bore in sixteenths of an inch at the end of the part number, so an NP-16 is a 1 inch bore and a MP-23 is 1 7/16 inches.

Mounted ball bearings slip fit onto the shaft: the shaft is slightly smaller and the bore slightly larger than the nominal size, so no press or heating is needed. The lock then depends on the shaft being held to size, and a ground finish is the normal recommendation. The shaft tolerances the two lines are designed around are below; a shaft outside them is not something a premium lock corrects.

Sealmaster Gold standard duty units run from 1/2 inch to 2 15/16 inches (20 mm to 75 mm) in the NP pillow block, and the medium duty MP series from 15/16 inch to 4 inches (25 mm to 100 mm). The standard duty insert number begins with 2 and the medium duty insert with 3, and a metric unit ends in the bore in millimeters divided by five, so NP-205 is a 25 mm bore. The shaft size conversion chart converts between fractions, decimals and millimeters, and the mounted bearing nomenclature guide reads the rest of the part number.

Which mounting style: pillow block, flange, take-up or hanger?

The mounting style follows the surface the housing bolts to and the direction the shaft runs. A pillow block bolts to a flat surface parallel to the shaft and is the most popular style, with two or four bolt holes; a flange bolts to a surface perpendicular to the shaft and is the second most popular, in two, three and four bolt patterns. Take-ups sit in a frame so the bearing position can be adjusted, and hanger bearings thread onto the end of a pipe and hang down to support a screw conveyor shaft.

Flange units are strongest when the load is applied toward the base, in thrust, and are often used on vertical shafts; a SF-16 is the four-bolt flange for a 1 inch shaft. Flange cartridges are made in four and six bolt styles, are strongest under radial load and withstand rotating radial loads in eccentric load situations. Take-up units are common on belt conveyors, where the frame adjusts belt tension: Sealmaster ST units such as the ST-16 have slotted sides that fit the STH take-up frame rails, and an acme threaded adjustment rod positions the bearing. Of the two hanger series, SCHB units carry the lubrication fitting inside the threaded shank for remote lubrication through the pipe, and SEHB units such as the SEHB-16 have grease fittings on the outside of the body; the BDZ suffix on an SEHB specifies tight internal clearance and housing fit for high vibration.

In these housing styles Browning numbers by duty: the 100 series is intermediate duty, the 200 series standard duty and the 300 series medium duty, so a VPS-216 is a standard duty two-bolt pillow block for a 1 inch shaft. Other Browning 100 series, including the L, LR and SL insert lines, are light duty. Where the machine supplies its own housing, a cylindrical OD insert in the insert bearings category is mounted in its cylindrical bore instead.

Setscrew, eccentric collar, Skwezloc concentric collar or adapter: which locking method?

A single setscrew lock is the most popular mounting method and suits moderate loads and speeds; a concentric locking collar is the choice for high speed, vibration reduction, runout control and stainless or hardened shafting; a double setscrew lock is the choice for heavy loads, high thrust and vertical shafts. An eccentric collar is a Browning option for a shaft that turns in one direction only, and an adapter mount is the alternative to a collar on mounted spherical roller bearings.

Where a cell says thrust device, a thrust collar or axial locating device is required with the friction grip lock.

The single lock has an extended inner ring on one side held to the shaft by two setscrews spaced 120 degrees apart, a balanced three point contact that minimizes inner ring distortion. It takes the least space on the shaft and is sometimes the only practical lock in a flange or cartridge housing where the back side is inaccessible. The double lock extends the inner ring on both sides and uses four screws; it is specified where lock reliability is critical, on high load, high thrust, vertical shaft, eccentric drive, high vibration and high speed applications, and it reduces fretting corrosion on the shaft. Both leave setscrew marks that are flattened with a punch before the bearing is removed. The Sealmaster suffix D denotes double setscrew locking, so an NPD is the double lock version of the NP-16 housing.

The Skwezloc concentric collar (Browning calls its version BOA) has an inner ring extension slit into six tangs; a split collar tightened by one Torx Plus head cap screw clamps them to the shaft with 360 degrees of holding. It centers the shaft in the bore, keeps the ball path round, does not mark the shaft, and is the lock specified for air handling, HVAC, fans, blowers, saws, routers and spindles where noise, vibration and runout matter. On a vertical shaft or under high thrust it needs a thrust collar or axial locating device, because the grip is friction alone. The Sealmaster suffix T denotes the Skwezloc collar: the NP-16T is the same housing and bore as the NP-16 with the concentric lock, and its maximum speed rating rises from 6,350 to 9,000 rpm. The current collar is designed for commercial turned and polished shafting at +.000 / -.003 inch on 1/2 to 2 inch shafts and +.000 / -.004 inch on 2 1/8 to 2 7/16 inch shafts, against the +.0000 / -.0005 and -.0010 inch tolerances of turned, ground and polished shafting, with the maximum speed on commercial shafting equal to setscrew locking.

The eccentric lock uses a collar with an eccentric bore that mates with an eccentric profile on the inner ring extension. The collar is turned in the direction of shaft rotation until the two profiles wedge into a friction grip, then a setscrew on the collar is tightened. It is available on Browning units only, and because rotation tightens it, it is not used where the shaft turns in both directions. Browning states the lock in the series letters: S is setscrew, B is the BOA concentric collar and E is eccentric, so the VPE-216 is the eccentric lock version of the VPS-216, and every product page lists the fitted lock under Shaft Locking Type. On mounted spherical roller bearings the choice is between a collar mount with setscrews at 120 degrees and an adapter mount, whose axial cap screws mount and dismount the bearing from one side with a hex key and torque wrench and no feeler gauges; the adapter mount is the A suffix, as in USRB5000A.

Two limits push the choice toward a Skwezloc or double lock: a load approaching the rating table figure at 5,000 hours life and 150 to 250 rpm, and a speed in the range of 80 to 100 percent of the maximum listed. In both cases the shaft size should be closely controlled, and at high load an EP grease may be required.

Which seal and housing material suit the environment?

Seals keep contamination out and lubricant in, and the right one depends on speed, the level and type of contamination, the temperature and the lubricant. A felt seal suits dry applications with light to moderate contamination and runs with less drag and less heat than a rubber contact seal; a non-contacting labyrinth seal suits dry, low contamination environments, reduces drag further and normally cannot be blown out by over-greasing; a contacting rubber lip seal is the choice for wet and dirty environments. Sealmaster Gold units ship with a felt seal and flinger as standard, and a contact seal is specified by adding the suffix C to the part number; Browning units ship with a contact seal, with a flinger on the 200 and 300 series.

The felt seal is two metal stampings around a felt washer. The outer flinger rotates with the shaft, slinging debris away from the seal and churning lubricant back toward the ball path, and the felt filters what gets past while letting oxidized grease purge during relubrication. Rubber lip seals are made in Buna N nitrile, FKM and silicone, with multiple lip versions for severe service: the Sealmaster DRT high contamination option carries a double or triple lip contact seal and a 100 percent grease fill. Every product page lists the seal type fitted, from Felt Labyrinth Seal to Single Lip Contact Seal with Flinger, Triple Lip Contact Seal and High Temp Labyrinth.

Gray cast iron is the most common housing material and has adequate strength for most applications, but it can be brittle under tensile forces and is not recommended where shock loads are present; ductile iron or cast steel is preferred for heavy loads, shock and vibration, at a slightly higher cost. Sealmaster hanger bearings are ductile iron as standard. Where humidity, moisture or chemicals are present, a coating or an alternative material is used: the housing materials on the product pages run from Cast Iron and Ductile Iron to Stainless Steel, Polyamide, Composite and Stamped Steel. Standard bearings are rated for -20 to 200 F on Browning and -20 to 220 F on Sealmaster Gold; the HT, HTA and HTC high temperature options extend that to 400 F with increased internal clearance and a synthetic grease, behind a Nomex seal on HT and HTA and a silicone fiberglass or FKM spring seal on HTC.

What else changes the choice: expansion, speed and noise?

A shaft that heats up grows in length, and one bearing on it must be free to let it. An expansion unit has an internal feature that lets the insert float axially in the housing; it is paired with a fixed unit at the drive end of the shaft, and both are recommended on the same shaft in high temperature applications. Not providing expansion where it is needed produces thrust loads the bearing was not selected for and shortens its life.

Sealmaster expansion units carry the prefix E, as in ENP-23, and share the mounting dimensions of the fixed unit; the expansion capability runs from 3/32 inch on the smallest bores to 7/16 inch at 4 7/16 inches. The product pages list each unit as Fixed or Expansion under the Fixed vs. Expansion specification. For fans and other light frames, the Sealmaster CXU air handling option adds a controlled housing fit that lets the bearing self-align on lightweight structures and a two stage noise test; the HS high speed option is offered in Skwezloc locking only, with a backed off felt seal and increased internal clearance. Once the bearing is chosen, how and how often it is greased is covered in the bearing lubrication basics guide.

When the load, speed or environment falls outside the ranges above, or the shaft is worn or out of tolerance, send the application details through the bearing selection support form and we will confirm the unit before you order. Ready to buy? Browse pillow blocks, two-bolt flanges and four-bolt flanges by bore, lock and seal.