Knurling – Meaning, Necessity, Types, Grade and Cutting Speed

In the ITI Turner trade, knurling is an important lathe operation used to produce a patterned surface on a workpiece. It is mainly used to improve grip and enhance the appearance of the component. Unlike cutting operations, knurling is a forming process in which material is displaced rather than removed. This chapter explains the meaning, necessity, types, grades, and cutting speed for knurling.

Meaning of Knurling

Knurling is a process of producing a regular pattern of ridges or indentations on the surface of a workpiece using a knurling tool. The pattern is formed by pressing hardened rollers against the rotating workpiece.

It is commonly performed on a lathe machine.

Principle of Knurling

Knurling works on the principle of plastic deformation. The knurling tool presses against the workpiece surface, displacing the material to form a pattern without removing it.

Necessity of Knurling

• Provides better grip on handles and knobs
• Improves appearance of components
• Prevents slipping during use
• Increases friction between surfaces

Types of Knurling

1. Straight Knurling

Produces straight parallel lines on the surface.

2. Diamond Knurling

Produces a diamond-shaped pattern by crossing two sets of lines.

3. Diagonal Knurling

Produces angled lines in one direction.

4. Cross Knurling

Combination of two diagonal patterns forming a cross design.

Grades of Knurling

Knurling patterns are classified into different grades based on the pitch and coarseness of the pattern:

• Fine Knurl: Small pitch, used for small components
• Medium Knurl: General-purpose use
• Coarse Knurl: Large pitch, used for heavy-duty components

Knurling Tool

A knurling tool consists of one or more hardened steel rollers with a specific pattern. These rollers press against the workpiece to form the knurl.

Cutting Speed for Knurling

Knurling is usually performed at low speeds compared to turning operations.

• Recommended speed: 10 to 30 m/min (depending on material)

Lower speeds are preferred to avoid excessive heat and ensure proper pattern formation.

Factors Affecting Knurling

• Material of workpiece
• Knurling pressure
• Speed of operation
• Type of knurling tool

Advantages of Knurling

• Improves grip
• Enhances appearance
• Simple operation
• No material removal

Limitations

• Increases diameter of workpiece
• Requires proper pressure control

Precautions While Knurling

• Use correct speed
• Apply sufficient pressure
• Use cutting fluid
• Ensure proper alignment of tool

Applications of Knurling

• Handles and knobs
• Tool grips
• Screw heads
• Machine components

Application in Turner Workshop

In the Turner trade, knurling is used to create rough surfaces for better grip and decorative purposes. It is commonly applied to handles, knobs, and shafts.

Proper selection of type and grade ensures effective results.

Conclusion

Knurling is an important forming operation in machining. It improves grip and enhances the appearance of components.

Understanding its types, grades, and cutting speed helps in achieving proper results.

In conclusion, mastering knurling techniques is essential for producing functional and high-quality components in the ITI Turner trade.