Short Answer:

Keys and keyways are common machine elements used to connect rotating parts like shafts and gears. In machine drawings, keys are represented as rectangular or square blocks along the shaft, and keyways are the matching slots cut into the shaft or hub to fit the key. These are shown in detailed views or sections with proper dimensions and notes.

Standard symbols, shapes, and conventions are used to clearly indicate the size, position, and type of key and keyway, ensuring that the parts fit together correctly during manufacturing and assembly.

Detailed Explanation:

Representation of keys and keyways in machine drawings

Keys and keyways are essential components for transmitting torque between shafts and other rotating parts such as gears, pulleys, or couplings. To avoid slipping and provide a secure connection, the key fits tightly into a keyway cut on both the shaft and the mating part. Proper representation of these features in technical drawings is critical to ensure correct manufacturing and assembly.

How keys are shown in drawings

Shape and location: Keys are shown as rectangular or square blocks placed along the shaft’s length.
Detailed views: Since keys are often hidden inside the shaft and hub, they are usually shown in sectional views or detailed enlarged views for clarity.
Dimensions: Length, width, and height (thickness) of the key are clearly dimensioned.
Types of keys: Common types such as parallel keys, Woodruff keys, and taper keys have standard shapes and are represented accordingly.

How keyways are shown in drawings

Slots on shaft and hub: Keyways appear as long grooves or slots cut into the shaft and mating hub.
Section views: Keyways are best shown in cross-section, revealing the exact profile and depth.
Dimensioning: The width and depth of the keyway, along with its position along the shaft, are dimensioned precisely.
Location details: Drawings often include notes about the length of keyways and their location relative to shoulders or other features.

Standard symbols and conventions

Hidden lines: If keys or keyways are not sectioned, hidden lines (dashed) are used to indicate their presence.
Leader lines and notes: Leader lines point to the key/keyway with labels or part numbers for identification.
Surface finish and tolerances: These may be added to control the fit between key and keyway.
Key fits: Information about clearance or interference fit is sometimes included.

Importance of proper representation

Ensures correct fit: Accurate drawings help machinists cut keyways and manufacture keys that fit perfectly.
Prevents assembly issues: Correct sizing and positioning avoid misalignment or slippage during operation.
Facilitates inspection: Clear drawings enable quality control to verify dimensions and tolerances.
Supports maintenance: Easy identification of key types and sizes helps in repair or replacement.

Additional notes in drawings

Drawing may specify material for keys.
Notes on heat treatment or surface coating if required.
Sometimes indicate tolerances and manufacturing methods (milling, broaching).
Indicate if keys are standard catalog parts or custom made.

Conclusion:

Keys and keyways are represented in machine drawings as rectangular blocks and matching slots on shafts and hubs, respectively. They are usually shown in detailed or sectional views with precise dimensions and notes to ensure proper fit and function. Proper representation is essential for manufacturing accuracy, assembly reliability, and effective maintenance. Clear and standard drawing conventions help avoid errors and ensure smooth mechanical operation.