Machine Design: Gears and Keys

Gear Types

• Two helical gears, one with a right-hand helix and the other with a left-hand helix, are equivalent to a double helical gear (or herringbone gear).

Bolt Specifications

• The nominal diameter of bolts typically refers to the major diameter, which is the largest diameter of the threaded portion.

Lubrication Types

• Manual or drip lubrication refers to lubrication by the application of grease or oil without using pressurized systems.

Mating of Cylindrical Parts

• The opposite of clearance in cylindrical part mating is known as interference when the internal member is larger than the external member.

Electromagnetic Brakes

• An electromagnetic brake uses an electromagnet to generate a force that slows down or stops a rotating wheel.

Stress-Strain Characteristics

• The stress-strain curve for a glass rod during a tensile test typically shows a brittle behavior, with minimal plastic deformation before fracture.

Gear Ratios

• The ratio of the number of teeth to the pitch diameter of a gear is called the gear's tooth density or gear ratio.

Key Types

• A woodruff key is commonly used where maximum torque capacity is desired due to its unique design.

Radial Distance

• The radial distance between the sharp crest of a gear tooth and the bounding cylinder is known as the addendum.

Quantities Description

• Exact quantities are those that are completely specified by their known magnitude, such as length or mass.

Stress Ratio

• The ratio of stress acting on an elastic material to the decrease in volume per unit volume is known as the bulk modulus.

Material Strength

• The ability of a material to withstand completely reversing loads is referred to as fatigue strength.

Pitch Circle Circumference Ratio

• The ratio of the circumference of the pitch circle to the number of teeth is referred to as the pitch of the gear.

Common Thread Types

• Unified National Thread is a type of thread commonly used in manufacturing for its standardized dimensions.

Thread Angle

• The angle included between the sides of a screw thread, measured in an axial plane, is typically 60 degrees for standard threads.

Tooth Space Depth

• The depth of tooth space below the pitch circle is termed the dedendum.

Material Strain Properties

• The property of a material relating lateral strain to longitudinal strain is known as the Poisson's ratio.

Twisting Strength

• The characteristic of a material to withstand forces causing twisting is referred to as its torsional strength.