Critical Thinking Strategies Quiz

Bearings

• Two basic types of bearings are used: friction and anti-friction.
• Friction bearings have a sliding contact between a shaft and the bearing.
• Anti-friction bearings have a rolling contact between a shaft and the bearing.
• Bearing housings are the outer casing.
• Common materials for housings are cast iron, cast steel, and fabricated steel.
• Bearing dimensions, style, speed, direction of pull, and support design are considered in choosing a bearing.

Friction Bearings

• Nominal sizes are often utilized, like "27/16" bearing.
• The size of the bore (ID) is a critical dimension for bearing installation and alignment.
• Bearing styles include solid and split bearings.

Solid Bearings

• Used with low speed and load.
• Frequently mounted in inverted positions.
• Require the bearing to be slid onto the shaft as a unit.

Split Bearings

• Used for medium to heavy loads.
• Various designs include two-bolt and four-bolt options.

Angle Bearings

• Used for drives when the direction of the load is parallel to, or at an angle to, the horizontal,
• Or when the bearing is mounted on a vertical support.

Integrated Bearings

• Common in industrial heavy-duty machines.
• The base of the bearing is cast as an integral part of the machine.

Liner Materials

• Metallic liners are typically used for medium-speed and light-to-heavy-load applications.
• Some common metallic liners include babbitt, brass, bronze, and aluminum.
• Non-metallic liners like nylon, polyurethane, and phenol laminates (e.g., Celoron™ and Micarta™) are sometimes used.

Liner Material Properties

• Liner material should be softer than the shaft material.
• Low coefficient of friction
• Wear resistant
• Good heat conductivity
• Readily available

Babbitt

• A common anti-friction lining material for bearings.
• Melts at around 288°C (550°F)..
• Fills cracks and irregularities.
• Can be used in badly worn bearing housings.

Metallic Liner Materials

• Babbitt
• Brass
• Bronze
• Aluminum
• Sintered bronze

Non-Metallic Liner Materials

• Nylon
• Polyurethane
• Phenol laminates

Bearing Housings

• The housing is sometimes called a pillow block.
• The parts include the base, base bolt slots, the cap, and the cap bolt holes.

Installing & Removing Bearings

• Bearings are installed square on the shaft.
• There are push fit and interference fit methods.

Bearing Clearance

• A small clearance is needed between the shaft and the bearing cap to prevent binding.
• Shims can be used to adjust clearance.

Bearing Removal

• Non-destructive methods use pullers or presses.
• Destructive removal involves cutting away the bearing rings using an oxyacetylene torch.

Thrust Control

• Thrust is controlled by shaft collars and thrust washers.

Kingsbury Thrust Bearings

• Specialized bearings for high-speed applications.
• Designs include fixed-pad and tilting-pad configurations.

Guide Bearings

• Used as a positioning or guidance device in linear motion.
• Often has a thin layer of bearing material.

Pivoted Shoe Bearings

• Used for high peripheral speeds and shaft stabilization.
• Cylindrical shapes for fitted grooves in a retaining ring.

Rolling Elements

• Ball bearings
• Roller bearings (cylindrical, tapered, spherical, needle)
• Spherical roller bearings: rollers curved across their width, running in concave channels.

Shields & Seals

• Prevent foreign materials in the housing.
• Open bearings: foreign materials are blocked by shaft lip seals or equivalent
• Shielded bearings: solids are blocked
• Sealed bearings: solids and fluids are blocked.

Lubrication

• Clean bearings before installing them.
• Oil or grease are common lubricants.

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